IPsec

In <a title="Computing" href="https://en.wikipedia.org/wiki/Computing">computing</a>, Internet Protocol Security (IPsec) is a secure network <a class="mw-redirect" title="Protocol suite" href="https://en.wikipedia.org/wiki/Protocol_suite">protocol suite</a> that <a title="Authentication" href="https://en.wikipedia.org/wiki/Authentication">authenticates</a> and <a title="Encryption" href="https://en.wikipedia.org/wiki/Encryption">encrypts</a> the <a class="mw-redirect" title="Packet (information technology)" href="https://en.wikipedia.org/wiki/Packet_(information_technology)">packets</a> of data sent over an <a title="Internet Protocol" href="https://en.wikipedia.org/wiki/Internet_Protocol">internet protocol</a> network. It is used in <a title="Virtual private network" href="https://en.wikipedia.org/wiki/Virtual_private_network">virtual private networks</a> (VPNs).

IPsec includes protocols for establishing <a title="Mutual authentication" href="https://en.wikipedia.org/wiki/Mutual_authentication">mutual authentication</a> between agents at the beginning of a session and negotiation of <a title="Key (cryptography)" href="https://en.wikipedia.org/wiki/Key_(cryptography)">cryptographic keys</a> to use during the session. IPsec can protect data flows between a pair of hosts (host-to-host), between a pair of security gateways (network-to-network), or between a security gateway and a host (network-to-host).<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc2406-1">[1]</a> Internet Protocol security (IPsec) uses cryptographic security services to protect communications over Internet Protocol (IP) networks. IPsec supports network-level peer authentication, data-origin authentication, data integrity, data confidentiality (encryption), and replay protection.

The initial <a title="IPv4" href="https://en.wikipedia.org/wiki/IPv4">IPv4</a> suite was developed with few security provisions. As a part of the IPv4 enhancement, IPsec is a layer 3 <a title="OSI model" href="https://en.wikipedia.org/wiki/OSI_model">OSI model</a> or <a class="mw-redirect" title="Internet Layer" href="https://en.wikipedia.org/wiki/Internet_Layer">Internet Layer</a> end-to-end security scheme, while some other Internet security systems in widespread use operate above layer 3, such as <a title="Transport Layer Security" href="https://en.wikipedia.org/wiki/Transport_Layer_Security">Transport Layer Security</a> (TLS) and <a title="Secure Shell" href="https://en.wikipedia.org/wiki/Secure_Shell">Secure Shell</a> (SSH), both of which operate at the Application layer. IPsec can automatically secure applications at the IP layer.

<h2>Contents</h2>

<ul>

<li class="toclevel-1 tocsection-1"><a href="https://en.wikipedia.org/wiki/IPsec#History">1History</a></li>

<li class="toclevel-1 tocsection-2"><a href="https://en.wikipedia.org/wiki/IPsec#Security_architecture">2Security architecture</a>

<ul>

<li class="toclevel-2 tocsection-3"><a href="https://en.wikipedia.org/wiki/IPsec#Authentication_Header">2.1Authentication Header</a></li>

<li class="toclevel-2 tocsection-4"><a href="https://en.wikipedia.org/wiki/IPsec#Encapsulating_Security_Payload">2.2Encapsulating Security Payload</a></li>

<li class="toclevel-2 tocsection-5"><a href="https://en.wikipedia.org/wiki/IPsec#Security_association">2.3Security association</a></li>

</ul>

</li>

<li class="toclevel-1 tocsection-6"><a href="https://en.wikipedia.org/wiki/IPsec#Modes_of_operation">3Modes of operation</a>

<ul>

<li class="toclevel-2 tocsection-7"><a href="https://en.wikipedia.org/wiki/IPsec#Transport_mode">3.1Transport mode</a></li>

<li class="toclevel-2 tocsection-8"><a href="https://en.wikipedia.org/wiki/IPsec#Tunnel_mode">3.2Tunnel mode</a></li>

</ul>

</li>

<li class="toclevel-1 tocsection-9"><a href="https://en.wikipedia.org/wiki/IPsec#Cryptographic_algorithms">4Cryptographic algorithms</a></li>

<li class="toclevel-1 tocsection-10"><a href="https://en.wikipedia.org/wiki/IPsec#Implementations">5Implementations</a></li>

<li class="toclevel-1 tocsection-11"><a href="https://en.wikipedia.org/wiki/IPsec#Standards_status">6Standards status</a></li>

<li class="toclevel-1 tocsection-12"><a href="https://en.wikipedia.org/wiki/IPsec#Alleged_NSA_interference">7Alleged NSA interference</a></li>

<li class="toclevel-1 tocsection-13"><a href="https://en.wikipedia.org/wiki/IPsec#IETF_documentation">8IETF documentation</a>

<ul>

<li class="toclevel-2 tocsection-14"><a href="https://en.wikipedia.org/wiki/IPsec#Standards_track">8.1Standards track</a></li>

<li class="toclevel-2 tocsection-15"><a href="https://en.wikipedia.org/wiki/IPsec#Experimental_RFCs">8.2Experimental RFCs</a></li>

<li class="toclevel-2 tocsection-16"><a href="https://en.wikipedia.org/wiki/IPsec#Informational_RFCs">8.3Informational RFCs</a></li>

<li class="toclevel-2 tocsection-17"><a href="https://en.wikipedia.org/wiki/IPsec#Best_current_practice_RFCs">8.4Best current practice RFCs</a></li>

<li class="toclevel-2 tocsection-18"><a href="https://en.wikipedia.org/wiki/IPsec#Obsolete/historic_RFCs">8.5Obsolete/historic RFCs</a></li>

</ul>

</li>

<li class="toclevel-1 tocsection-20"><a href="https://en.wikipedia.org/wiki/IPsec#References">10References</a></li>

<li class="toclevel-1 tocsection-21"><a href="https://en.wikipedia.org/wiki/IPsec#External_links">11External links</a></li>

</ul>

</div>

<h2>History[<a title="Edit section: History" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=1">edit</a>]</h2>

From 1986 to 1991, the NSA sponsored the development of security protocols for the Internet under its Secure Data Network Systems (SDNS) program.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-2">[2]</a> This brought together various vendors including Motorola who produced a network encryption device in 1988. The work was openly published from about 1988 by <a title="National Institute of Standards and Technology" href="https://en.wikipedia.org/wiki/National_Institute_of_Standards_and_Technology">NIST</a> and, of these, Security Protocol at Layer 3 (SP3) would eventually morph into the ISO standard Network Layer Security Protocol (NLSP).<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-3">[3]</a>

From 1992 to 1995, various research groups improved upon SDNS's SP3. In 1992, the US <a class="mw-redirect" title="Naval Research Laboratory" href="https://en.wikipedia.org/wiki/Naval_Research_Laboratory">Naval Research Laboratory</a> (NRL) began the SIPP project to research and implement IP encryption. In December 1993, the experimental <a title="SwIPe (protocol)" href="https://en.wikipedia.org/wiki/SwIPe_(protocol)">Software IP Encryption Protocol</a> (swIPe) was developed on <a title="SunOS" href="https://en.wikipedia.org/wiki/SunOS">SunOS</a> at <a title="Columbia University" href="https://en.wikipedia.org/wiki/Columbia_University">Columbia University</a> and <a class="mw-redirect" title="AT&T Bell Labs" href="https://en.wikipedia.org/wiki/AT%26T_Bell_Labs">AT&T Bell Labs</a> by John Ioannidis and others. Funded by the <a title="White House" href="https://en.wikipedia.org/wiki/White_House">White House</a> in 1993, Wei Xu at <a title="Trusted Information Systems" href="https://en.wikipedia.org/wiki/Trusted_Information_Systems">Trusted Information Systems</a> (TIS) followed the swIPe research,<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-4">[4]</a> enhanced the IP security protocols and developed the <a title="Device driver" href="https://en.wikipedia.org/wiki/Device_driver">device driver</a> of <a title="Data Encryption Standard" href="https://en.wikipedia.org/wiki/Data_Encryption_Standard">Data Encryption Standard</a>. By December 1994, his team released the TIS Gauntlet Firewall product with the integrated <a title="Triple DES" href="https://en.wikipedia.org/wiki/Triple_DES">3DES</a> hardware encryption and provided commercial IP Security at over <a title="Digital Signal 1" href="https://en.wikipedia.org/wiki/Digital_Signal_1">T1</a> speeds, securing networks between the US East and West coasts.

During this period the <a title="Internet Engineering Task Force" href="https://en.wikipedia.org/wiki/Internet_Engineering_Task_Force">Internet Engineering Task Force</a> (IETF) IP Security Working Group formed<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-5">[5]</a> to standardize these efforts as an open, freely available set of security extensions, called IPsec.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-6">[6]</a> In 1995, the working group published RFC-1825 through RFC-1827 with the NRL having the first working implementation.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-7">[7]</a>

<h2>Security architecture[<a title="Edit section: Security architecture" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=2">edit</a>]</h2>

The IPsec is an <a title="Open standard" href="https://en.wikipedia.org/wiki/Open_standard">open standard</a> as a part of the IPv4 suite. IPsec uses the following <a class="mw-redirect" title="Protocol (computing)" href="https://en.wikipedia.org/wiki/Protocol_(computing)">protocols</a> to perform various functions:<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc2411-8">[8]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc4308-9">[9]</a>

<ul>

<li><a href="https://en.wikipedia.org/wiki/IPsec#Authentication_Header">Authentication Headers (AH)</a> provides connectionless <a title="Data integrity" href="https://en.wikipedia.org/wiki/Data_integrity">data integrity</a> and <a class="mw-redirect" title="Data origin authentication" href="https://en.wikipedia.org/wiki/Data_origin_authentication">data origin authentication</a> for IP <a class="mw-redirect" title="Datagrams" href="https://en.wikipedia.org/wiki/Datagrams">datagrams</a> and provides protection against <a title="Replay attack" href="https://en.wikipedia.org/wiki/Replay_attack">replay attacks</a>.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc2402-10">[10]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc4302-11">[11]</a></li>

<li><a href="https://en.wikipedia.org/wiki/IPsec#Encapsulating_Security_Payload">Encapsulating Security Payloads (ESP)</a> provides <a title="Confidentiality" href="https://en.wikipedia.org/wiki/Confidentiality">confidentiality</a>, connectionless <a title="Integrity" href="https://en.wikipedia.org/wiki/Integrity">integrity</a>, data-origin <a title="Authentication" href="https://en.wikipedia.org/wiki/Authentication">authentication</a>, an anti-replay service (a form of partial sequence integrity), and limited traffic-flow confidentiality.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc2406-1">[1]</a></li>

<li><a href="https://en.wikipedia.org/wiki/IPsec#Security_association">Security Associations (SA)</a> provides the bundle of algorithms and data that provide the parameters necessary for AH and/or ESP operations. The <a title="Internet Security Association and Key Management Protocol" href="https://en.wikipedia.org/wiki/Internet_Security_Association_and_Key_Management_Protocol">Internet Security Association and Key Management Protocol</a> (ISAKMP) provides a framework for authentication and key exchange,<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc2409_sec1-12">[12]</a> with actual authenticated keying material provided either by manual configuration with <a title="Pre-shared key" href="https://en.wikipedia.org/wiki/Pre-shared_key">pre-shared keys</a>, <a title="Internet Key Exchange" href="https://en.wikipedia.org/wiki/Internet_Key_Exchange">Internet Key Exchange</a> (IKE and IKEv2), <a title="Kerberized Internet Negotiation of Keys" href="https://en.wikipedia.org/wiki/Kerberized_Internet_Negotiation_of_Keys">Kerberized Internet Negotiation of Keys</a> (KINK), or IPSECKEY <a title="List of DNS record types" href="https://en.wikipedia.org/wiki/List_of_DNS_record_types">DNS records</a>.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc2409-13">[13]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc4306-14">[14]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc4430-15">[15]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-RFC_4025-16">[16]</a></li>

</ul>

<h3>Authentication Header[<a title="Edit section: Authentication Header" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=3">edit</a>]</h3>

The Security Authentication Header (<a href="https://en.wikipedia.org/wiki/IPsec#Authentication_Header">AH</a>) is derived partially from previous IETF standards work for authentication of the <a title="Simple Network Management Protocol" href="https://en.wikipedia.org/wiki/Simple_Network_Management_Protocol">Simple Network Management Protocol</a> (SNMP) version 2. Authentication Header (AH) is a member of the IPsec protocol suite. AH ensures connectionless <a title="Data integrity" href="https://en.wikipedia.org/wiki/Data_integrity">integrity</a> by using a <a title="Hash function" href="https://en.wikipedia.org/wiki/Hash_function">hash function</a> and a secret shared key in the AH algorithm. AH also guarantees the data origin by <a class="mw-redirect" title="Authenticating" href="https://en.wikipedia.org/wiki/Authenticating">authenticating</a> IP <a class="mw-redirect" title="Packet (information technology)" href="https://en.wikipedia.org/wiki/Packet_(information_technology)">packets</a>. Optionally a sequence number can protect the IPsec packet's contents against <a title="Replay attack" href="https://en.wikipedia.org/wiki/Replay_attack">replay attacks</a>,<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-17">[17]</a> using the <a class="mw-redirect" title="Sliding window" href="https://en.wikipedia.org/wiki/Sliding_window">sliding window</a> technique and discarding old packets.

<ul>

<li>In <a title="IPv4" href="https://en.wikipedia.org/wiki/IPv4">IPv4</a>, AH prevents option-insertion attacks. In <a title="IPv6" href="https://en.wikipedia.org/wiki/IPv6">IPv6</a>, AH protects both against header insertion attacks and option insertion attacks.</li>

<li>In <a title="IPv4" href="https://en.wikipedia.org/wiki/IPv4">IPv4</a>, the AH protects the IP payload and all header fields of an IP datagram except for mutable fields (i.e. those that might be altered in transit), and also IP options such as the IP Security Option (<a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc1108" rel="nofollow">RFC 1108</a>). Mutable (and therefore unauthenticated) IPv4 header fields are <a class="mw-redirect" title="Differentiated services code point" href="https://en.wikipedia.org/wiki/Differentiated_services_code_point">DSCP</a>/<a title="Type of service" href="https://en.wikipedia.org/wiki/Type_of_service">ToS</a>, <a title="Explicit Congestion Notification" href="https://en.wikipedia.org/wiki/Explicit_Congestion_Notification">ECN</a>, Flags, <a title="IP fragmentation" href="https://en.wikipedia.org/wiki/IP_fragmentation">Fragment</a> <a title="Offset (computer science)" href="https://en.wikipedia.org/wiki/Offset_(computer_science)">Offset</a>, <a title="Time to live" href="https://en.wikipedia.org/wiki/Time_to_live">TTL</a> and <a title="IPv4 header checksum" href="https://en.wikipedia.org/wiki/IPv4_header_checksum">Header Checksum</a>.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc4302-11">[11]</a></li>

<li>In <a title="IPv6" href="https://en.wikipedia.org/wiki/IPv6">IPv6</a>, the AH protects most of the IPv6 base header, AH itself, non-mutable extension headers after the AH, and the IP payload. Protection for the IPv6 header excludes the mutable fields: <a class="mw-redirect" title="Differentiated services code point" href="https://en.wikipedia.org/wiki/Differentiated_services_code_point">DSCP</a>, <a title="Explicit Congestion Notification" href="https://en.wikipedia.org/wiki/Explicit_Congestion_Notification">ECN</a>, Flow Label, and Hop Limit.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc4302-11">[11]</a></li>

</ul>

AH operates directly on top of IP, using IP protocol number 51.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-iana-18">[18]</a>

The following AH packet diagram shows how an AH packet is constructed and interpreted:<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc2402-10">[10]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc4302-11">[11]</a>

<table class="wikitable"><caption>Authentication Header formatOffsetsOctet160123Octet16Bit1001234567891011121314151617181920212223242526272829303100Next</caption>

<tbody>

<tr>

</tr>

<tr>

</tr>

<tr>

<td colspan="8"> HeaderPayload</td>

<td colspan="8"> LenReserved432Security</td>

</tr>

<tr>

<td colspan="32"> Parameters Index (SPI)</td>

</tr>

<tr>

<th>864Sequence</th>

<td colspan="32"> NumberC96Integrity</td>

</tr>

<tr>

<td colspan="32" rowspan="2"> Check Value (ICV)
...</td>

</tr>

<tr>

</tr>

</tbody>

</table>

</center>

<dl>

<dt>Next Header (8 bits) </dt>

<dd>Type of the next header, indicating what upper-layer protocol was protected. The value is taken from the <a title="List of IP protocol numbers" href="https://en.wikipedia.org/wiki/List_of_IP_protocol_numbers">list of IP protocol numbers</a>.</dd>

<dt>Payload Len (8 bits) </dt>

<dd>The length of this Authentication Header in 4-octet units, minus 2. For example, an AH value of 4 equals 3×(32-bit fixed-length AH fields) + 3×(32-bit ICV fields) − 2 and thus an AH value of 4 means 24 octets. Although the size is measured in 4-octet units, the length of this header needs to be a multiple of 8 octets if carried in an IPv6 packet. This restriction does not apply to an Authentication Header carried in an IPv4 packet.Reserved</dd>

<dd>Reserved for future use (all zeroes until then).Security</dd>

<dt> Parameters Index (32 bits) </dt>

<dd>Arbitrary value which is used (together with the destination IP address) to identify the <a title="Security association" href="https://en.wikipedia.org/wiki/Security_association">security association</a> of the receiving party.</dd>

<dt>Sequence Number (32 bits) </dt>

<dd>A <a class="mw-redirect" title="Monotonic" href="https://en.wikipedia.org/wiki/Monotonic">monotonic</a> strictly increasing sequence number (incremented by 1 for every packet sent) to prevent <a title="Replay attack" href="https://en.wikipedia.org/wiki/Replay_attack">replay attacks</a>. When replay detection is enabled, sequence numbers are never reused, because a new security association must be renegotiated before an attempt to increment the sequence number beyond its maximum value.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc4302-11">[11]</a></dd>

<dt>Integrity Check Value (multiple of 32 bits) </dt>

<dd>Variable length check value. It may contain padding to align the field to an 8-octet boundary for <a title="IPv6" href="https://en.wikipedia.org/wiki/IPv6">IPv6</a>, or a 4-octet boundary for <a title="IPv4" href="https://en.wikipedia.org/wiki/IPv4">IPv4</a>.</dd>

</dl>

<h3>Encapsulating Security Payload[<a title="Edit section: Encapsulating Security Payload" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=4">edit</a>]</h3>

The IP Encapsulating Security Payload (ESP)<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-19">[19]</a> was researched at the <a class="mw-redirect" title="Naval Research Laboratory" href="https://en.wikipedia.org/wiki/Naval_Research_Laboratory">Naval Research Laboratory</a> starting in 1992 as part of a <a title="DARPA" href="https://en.wikipedia.org/wiki/DARPA">DARPA</a>-sponsored research project, and was openly published by <a class="mw-redirect" title="IETF" href="https://en.wikipedia.org/wiki/IETF">IETF</a> SIPP<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-20">[20]</a> Working Group drafted in December 1993 as a security extension for SIPP. This <a href="https://en.wikipedia.org/wiki/IPsec#Encapsulating_Security_Payload">ESP</a> was originally derived from the US Department of Defense <a class="new" title="SP3D (page does not exist)" href="https://en.wikipedia.org/w/index.php?title=SP3D&action=edit&redlink=1">SP3D</a> protocol, rather than being derived from the ISO Network-Layer Security Protocol (NLSP). The SP3D protocol specification was published by <a class="mw-redirect" title="NIST" href="https://en.wikipedia.org/wiki/NIST">NIST</a> in the late 1980s, but designed by the Secure Data Network System project of the US Department of Defense. Encapsulating Security Payload (ESP) is a member of the IPsec protocol suite. It provides origin <a title="Information security" href="https://en.wikipedia.org/wiki/Information_security#Authenticity">authenticity</a> through source <a title="Authentication" href="https://en.wikipedia.org/wiki/Authentication">authentication</a>, <a title="Data integrity" href="https://en.wikipedia.org/wiki/Data_integrity">data integrity</a> through hash functions and <a title="Confidentiality" href="https://en.wikipedia.org/wiki/Confidentiality">confidentiality</a> through <a title="Encryption" href="https://en.wikipedia.org/wiki/Encryption">encryption</a> protection for IP <a class="mw-redirect" title="Packet (information technology)" href="https://en.wikipedia.org/wiki/Packet_(information_technology)">packets</a>. ESP also supports <a title="Encryption" href="https://en.wikipedia.org/wiki/Encryption">encryption</a>-only and <a title="Authentication" href="https://en.wikipedia.org/wiki/Authentication">authentication</a>-only configurations, but using encryption without authentication is strongly discouraged because it is insecure.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-21">[21]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-22">[22]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-23">[23]</a>

Unlike <a class="mw-redirect" title="Authentication Header" href="https://en.wikipedia.org/wiki/Authentication_Header">Authentication Header (AH)</a>, ESP in transport mode does not provide integrity and authentication for the entire <a class="mw-redirect mw-disambig" title="IP packet (disambiguation)" href="https://en.wikipedia.org/wiki/IP_packet_(disambiguation)">IP packet</a>. However, in <a title="Tunneling protocol" href="https://en.wikipedia.org/wiki/Tunneling_protocol">Tunnel Mode</a>, where the entire original IP packet is <a title="Information hiding" href="https://en.wikipedia.org/wiki/Information_hiding">encapsulated</a> with a new packet header added, ESP protection is afforded to the whole inner IP packet (including the inner header) while the outer header (including any outer IPv4 options or IPv6 extension headers) remains unprotected. ESP operates directly on top of IP, using IP protocol number 50.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-iana-18">[18]</a>

The following ESP packet diagram shows how an ESP packet is constructed and interpreted:<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc2406-1">[1]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc4303-24">[24]</a>

<table class="wikitable"><caption>Encapsulating Security Payload format</caption>

<tbody>

<tr>

<th>Offsets</th>

<th>Octet16</th>

</tr>

<tr>

<th>Octet16</th>

</tr>

<tr>

<td colspan="32">Security Parameters Index (SPI)</td>

</tr>

<tr>

<th>432Sequence</th>

<td colspan="32"> Number864Payload</td>

</tr>

<tr>

</tr>

<tr>

</tr>

<tr>

</tr>

<tr>

<td colspan="16">Padding (0-255 octets)</td>

</tr>

<tr>

<td colspan="8">Pad LengthNext</td>

<td colspan="8"> Header......Integrity</td>

</tr>

<tr>

<td colspan="32" rowspan="2"> Check Value (ICV)
...</td>

</tr>

<tr>

</tr>

</tbody>

</table>

</center>

<dl>

<dt>Security Parameters Index (32 bits) </dt>

<dd>Arbitrary value used (together with the destination IP address) to identify the <a title="Security association" href="https://en.wikipedia.org/wiki/Security_association">security association</a> of the receiving party.</dd>

<dt>Sequence Number (32 bits) </dt>

<dd>A <a class="mw-redirect" title="Monotonic" href="https://en.wikipedia.org/wiki/Monotonic">monotonically</a> increasing sequence number (incremented by 1 for every packet sent) to protect against <a title="Replay attack" href="https://en.wikipedia.org/wiki/Replay_attack">replay attacks</a>. There is a separate counter kept for every security association.</dd>

<dt>Payload data (variable) </dt>

<dd>The protected contents of the original IP packet, including any data used to protect the contents (e.g. an Initialisation Vector for the cryptographic algorithm). The type of content that was protected is indicated by the Next Header field.Padding</dd>

<dt> (0-255 octets) </dt>

<dd>Padding for encryption, to extend the payload data to a size that fits the encryption's <a title="Block cipher" href="https://en.wikipedia.org/wiki/Block_cipher">cipher</a> block size, and to align the next field.</dd>

<dt>Pad Length (8 bits) </dt>

<dd>Size of the padding (in octets).Next</dd>

<dt> Header (8 bits) </dt>

<dd>Type of the next header. The value is taken from the <a title="List of IP protocol numbers" href="https://en.wikipedia.org/wiki/List_of_IP_protocol_numbers">list of IP protocol numbers</a>.</dd>

<dt>Integrity Check Value (multiple of 32 bits) </dt>

</dl>

<h3>Security association[<a title="Edit section: Security association" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=5">edit</a>]</h3>

<div class="hatnote navigation-not-searchable">Main article: <a title="Security association" href="https://en.wikipedia.org/wiki/Security_association">Security association</a></div>

The IPsec protocols use a <a title="Security association" href="https://en.wikipedia.org/wiki/Security_association">security association</a>, where the communicating parties establish shared security attributes such as <a class="mw-redirect" title="Algorithms" href="https://en.wikipedia.org/wiki/Algorithms">algorithms</a> and keys. As such IPsec provides a range of options once it has been determined whether AH or ESP is used. Before exchanging data the two hosts agree on which algorithm is used to encrypt the IP packet, for example <a title="Data Encryption Standard" href="https://en.wikipedia.org/wiki/Data_Encryption_Standard">DES</a> or <a title="International Data Encryption Algorithm" href="https://en.wikipedia.org/wiki/International_Data_Encryption_Algorithm">IDEA</a>, and which hash function is used to ensure the integrity of the data, such as <a title="MD5" href="https://en.wikipedia.org/wiki/MD5">MD5</a> or <a title="Secure Hash Algorithms" href="https://en.wikipedia.org/wiki/Secure_Hash_Algorithms">SHA</a>. These parameters are agreed for the particular session, for which a lifetime must be agreed and a <a title="Session key" href="https://en.wikipedia.org/wiki/Session_key">session key</a>.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-25">[25]</a>

The algorithm for authentication is also agreed before the data transfer takes place and IPsec supports a range of methods. Authentication is possible through <a title="Pre-shared key" href="https://en.wikipedia.org/wiki/Pre-shared_key">pre-shared key</a>, where a <a class="mw-redirect" title="Symmetric key" href="https://en.wikipedia.org/wiki/Symmetric_key">symmetric key</a> is already in the possession of both hosts, and the hosts send each other hashes of the shared key to prove that they are in possession of the same key. IPsec also supports <a class="mw-redirect" title="Public key encryption" href="https://en.wikipedia.org/wiki/Public_key_encryption">public key encryption</a>, where each host has a public and a private key, they exchange their public keys and each host sends the other a <a title="Cryptographic nonce" href="https://en.wikipedia.org/wiki/Cryptographic_nonce">nonce</a> encrypted with the other host's public key. Alternatively if both hosts hold a <a title="Public key certificate" href="https://en.wikipedia.org/wiki/Public_key_certificate">public key certificate</a>from a <a title="Certificate authority" href="https://en.wikipedia.org/wiki/Certificate_authority">certificate authority</a>, this can be used for IPsec authentication.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-26">[26]</a>

The security associations of IPsec are established using the <a title="Internet Security Association and Key Management Protocol" href="https://en.wikipedia.org/wiki/Internet_Security_Association_and_Key_Management_Protocol">Internet Security Association and Key Management Protocol</a> (ISAKMP). ISAKMP is implemented by manual configuration with pre-shared secrets, <a title="Internet Key Exchange" href="https://en.wikipedia.org/wiki/Internet_Key_Exchange">Internet Key Exchange</a> (IKE and IKEv2), <a title="Kerberized Internet Negotiation of Keys" href="https://en.wikipedia.org/wiki/Kerberized_Internet_Negotiation_of_Keys">Kerberized Internet Negotiation of Keys</a> (KINK), and the use of IPSECKEY <a title="List of DNS record types" href="https://en.wikipedia.org/wiki/List_of_DNS_record_types">DNS records</a>.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-RFC_4025-16">[16]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-27">[27]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-28">[28]</a> <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc5386" rel="nofollow">RFC 5386</a> defines Better-Than-Nothing Security (BTNS) as an unauthenticated mode of IPsec using an extended IKE protocol.

In order to decide what protection is to be provided for an outgoing packet, IPsec uses the <a title="Security Parameter Index" href="https://en.wikipedia.org/wiki/Security_Parameter_Index">Security Parameter Index</a> (SPI), an index to the security association database (SADB), along with the destination address in a packet header, which together uniquely identifies a security association for that packet. A similar procedure is performed for an incoming packet, where IPsec gathers decryption and verification keys from the security association database.

For <a title="IP multicast" href="https://en.wikipedia.org/wiki/IP_multicast">IP multicast</a> a security association is provided for the group, and is duplicated across all authorized receivers of the group. There may be more than one security association for a group, using different SPIs, thereby allowing multiple levels and sets of security within a group. Indeed, each sender can have multiple security associations, allowing authentication, since a receiver can only know that someone knowing the keys sent the data. Note that the relevant standard does not describe how the association is chosen and duplicated across the group; it is assumed that a responsible party will have made the choice.

<h2>Modes of operation[<a title="Edit section: Modes of operation" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=6">edit</a>]</h2>

The IPsec protocols AH and ESP can be implemented in a host-to-host transport mode, as well as in a network tunneling mode.

IPsec Modes</div>

</div>

<h3>Transport mode[<a title="Edit section: Transport mode" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=7">edit</a>]</h3>

In transport mode, only the payload of the IP packet is usually <a class="mw-redirect" title="Encrypted" href="https://en.wikipedia.org/wiki/Encrypted">encrypted</a> or authenticated. The routing is intact, since the IP header is neither modified nor encrypted; however, when the <a class="mw-redirect" title="Authentication Header" href="https://en.wikipedia.org/wiki/Authentication_Header">authentication header</a> is used, the IP addresses cannot be modified by <a title="Network address translation" href="https://en.wikipedia.org/wiki/Network_address_translation">network address translation</a>, as this always invalidates the <a class="mw-redirect" title="Hash value" href="https://en.wikipedia.org/wiki/Hash_value">hash value</a>. The <a title="Transport layer" href="https://en.wikipedia.org/wiki/Transport_layer">transport</a> and <a title="Application layer" href="https://en.wikipedia.org/wiki/Application_layer">application</a> layers are always secured by a hash, so they cannot be modified in any way, for example by <a class="mw-redirect" title="Port address translation" href="https://en.wikipedia.org/wiki/Port_address_translation">translating</a> the <a class="mw-redirect" title="TCP and UDP port" href="https://en.wikipedia.org/wiki/TCP_and_UDP_port">port</a> numbers.

A means to encapsulate IPsec messages for <a title="NAT traversal" href="https://en.wikipedia.org/wiki/NAT_traversal">NAT traversal</a> has been defined by <a title="Request for Comments" href="https://en.wikipedia.org/wiki/Request_for_Comments">RFC</a> documents describing the <a class="mw-redirect" title="NAT-T" href="https://en.wikipedia.org/wiki/NAT-T">NAT-T</a> mechanism.

<h3>Tunnel mode[<a title="Edit section: Tunnel mode" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=8">edit</a>]</h3>

<div class="hatnote navigation-not-searchable">Main article: <a title="Tunneling protocol" href="https://en.wikipedia.org/wiki/Tunneling_protocol">Tunneling protocol</a></div>

In tunnel mode, the entire IP packet is encrypted and authenticated. It is then encapsulated into a new IP packet with a new IP header. Tunnel mode is used to create <a title="Virtual private network" href="https://en.wikipedia.org/wiki/Virtual_private_network">virtual private networks</a> for network-to-network communications (e.g. between routers to link sites), host-to-network communications (e.g. remote user access) and host-to-host communications (e.g. private chat).<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-29">[29]</a>

Tunnel mode supports NAT traversal.

<h2>Cryptographic algorithms[<a title="Edit section: Cryptographic algorithms" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=9">edit</a>]</h2>

Cryptographic algorithms defined for use with IPsec include:

<ul>

<li><a title="HMAC" href="https://en.wikipedia.org/wiki/HMAC">HMAC</a>-<a class="mw-redirect" title="SHA1" href="https://en.wikipedia.org/wiki/SHA1">SHA1</a>/<a class="mw-redirect" title="SHA2" href="https://en.wikipedia.org/wiki/SHA2">SHA2</a> for integrity protection and authenticity.</li>

<li><a class="mw-redirect" title="TripleDES" href="https://en.wikipedia.org/wiki/TripleDES">TripleDES</a>-<a class="mw-redirect" title="Cipher block chaining" href="https://en.wikipedia.org/wiki/Cipher_block_chaining">CBC</a> for confidentiality</li>

<li><a title="Advanced Encryption Standard" href="https://en.wikipedia.org/wiki/Advanced_Encryption_Standard">AES</a>-CBC for confidentiality.</li>

<li>AES-<a title="Galois/Counter Mode" href="https://en.wikipedia.org/wiki/Galois/Counter_Mode">GCM</a> providing confidentiality and authentication together efficiently.</li>

</ul>

Refer to [<a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc8221" rel="nofollow">RFC 8221</a>] for details.

<h2>Implementations[<a title="Edit section: Implementations" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=10">edit</a>]</h2>

The IPsec can be implemented in the IP stack of an <a title="Operating system" href="https://en.wikipedia.org/wiki/Operating_system">operating system</a>, which requires modification of the source code. This method of implementation is done for hosts and security gateways. Various IPsec capable IP stacks are available from companies, such as HP or IBM.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-30">[30]</a> An alternative is so called <a class="new" title="Bump-in-the-stack (page does not exist)" href="https://en.wikipedia.org/w/index.php?title=Bump-in-the-stack&action=edit&redlink=1">bump-in-the-stack</a> (BITS) implementation, where the operating system source code does not have to be modified. Here IPsec is installed between the IP stack and the network <a title="Device driver" href="https://en.wikipedia.org/wiki/Device_driver">drivers</a>. This way operating systems can be retrofitted with IPsec. This method of implementation is also used for both hosts and gateways. However, when retrofitting IPsec the encapsulation of IP packets may cause problems for the automatic <a class="mw-redirect" title="Path MTU discovery" href="https://en.wikipedia.org/wiki/Path_MTU_discovery">path MTU discovery</a>, where the <a title="Maximum transmission unit" href="https://en.wikipedia.org/wiki/Maximum_transmission_unit">maximum transmission unit</a> (MTU) size on the network path between two IP hosts is established. If a host or gateway has a separate <a class="mw-redirect" title="Cryptoprocessor" href="https://en.wikipedia.org/wiki/Cryptoprocessor">cryptoprocessor</a>, which is common in the military and can also be found in commercial systems, a so-called <a title="Bump-in-the-wire" href="https://en.wikipedia.org/wiki/Bump-in-the-wire">bump-in-the-wire</a> (BITW) implementation of IPsec is possible.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-31">[31]</a>

When IPsec is implemented in the <a class="mw-redirect" title="Kernel (computer science)" href="https://en.wikipedia.org/wiki/Kernel_(computer_science)">kernel</a> the key management and <a class="mw-redirect" title="ISAKMP" href="https://en.wikipedia.org/wiki/ISAKMP">ISAKMP</a>/<a title="Internet Key Exchange" href="https://en.wikipedia.org/wiki/Internet_Key_Exchange">IKE</a> negotiation is carried out from user space. The openly specified "PF_KEY Key Management API, Version 2" is often used to enable the application-space key management application to update the IPsec Security Associations stored within the kernel-space IPsec implementation.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc2367-32">[32]</a> Existing IPsec implementations usually include ESP, AH, and IKE version 2. Existing IPsec implementations on UNIX-like operating systems, for example, Solaris or Linux, usually include PF_KEY version 2.

Embedded IPsec can be used to ensure the secure communication among applications running over constrained resource systems with a small overhead.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-33">[33]</a>

<h2>Standards status[<a title="Edit section: Standards status" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=11">edit</a>]</h2>

IPsec was developed in conjunction with <a title="IPv6" href="https://en.wikipedia.org/wiki/IPv6">IPv6</a> and was originally required to be supported by all standards-compliant implementations of <a title="IPv6" href="https://en.wikipedia.org/wiki/IPv6">IPv6</a> before <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc6434" rel="nofollow">RFC 6434</a> made it only a recommendation.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-rfc6434-34">[34]</a> IPsec is also optional for <a title="IPv4" href="https://en.wikipedia.org/wiki/IPv4">IPv4</a> implementations. IPsec is most commonly used to secure IPv4 traffic.[<a title="Wikipedia:Citation needed" href="https://en.wikipedia.org/wiki/Wikipedia:Citation_needed">citation needed</a>]

IPsec protocols were originally defined in <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc1825" rel="nofollow">RFC 1825</a> through <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc1829" rel="nofollow">RFC 1829</a>, which were published in 1995. In 1998, these documents were superseded by <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2401" rel="nofollow">RFC 2401</a> and <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2412" rel="nofollow">RFC 2412</a> with a few incompatible engineering details, although they were conceptually identical. In addition, a mutual authentication and key exchange protocol <a title="Internet Key Exchange" href="https://en.wikipedia.org/wiki/Internet_Key_Exchange">Internet Key Exchange</a> (IKE) was defined to create and manage security associations. In December 2005, new standards were defined in <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4301" rel="nofollow">RFC 4301</a> and <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4309" rel="nofollow">RFC 4309</a> which are largely a superset of the previous editions with a second version of the Internet Key Exchange standard <a class="mw-redirect" title="IKEv2" href="https://en.wikipedia.org/wiki/IKEv2">IKEv2</a>. These third-generation documents standardized the abbreviation of IPsec to uppercase “IP” and lowercase “sec”. “ESP” generally refers to <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4303" rel="nofollow">RFC 4303</a>, which is the most recent version of the specification.

Since mid-2008, an IPsec Maintenance and Extensions (ipsecme) working group is active at the IETF.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-35">[35]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-36">[36]</a>

<h2>Alleged NSA interference[<a title="Edit section: Alleged NSA interference" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=12">edit</a>]</h2>

In 2013, as part of <a class="mw-redirect" title="2013 mass surveillance disclosures" href="https://en.wikipedia.org/wiki/2013_mass_surveillance_disclosures">Snowden leaks</a>, it was revealed that the US <a title="National Security Agency" href="https://en.wikipedia.org/wiki/National_Security_Agency">National Security Agency</a> had been actively working to "Insert vulnerabilities into commercial encryption systems, IT systems, networks, and endpoint communications devices used by targets" as part of the <a class="mw-redirect" title="Bullrun (code name)" href="https://en.wikipedia.org/wiki/Bullrun_(code_name)">Bullrun</a> program.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-37">[37]</a> There are allegations that IPsec was a targeted encryption system.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-gilmore_bullrun-38">[38]</a>

The OpenBSD IPsec stack was the first implementation that was available under a permissive open-source license, and was therefore copied widely. In a letter which OpenBSD lead developer <a title="Theo de Raadt" href="https://en.wikipedia.org/wiki/Theo_de_Raadt">Theo de Raadt</a> received on 11 Dec 2010 from Gregory Perry, it is alleged that Jason Wright and others, working for the FBI, inserted "a number of <a title="Backdoor (computing)" href="https://en.wikipedia.org/wiki/Backdoor_(computing)">backdoors</a> and <a class="mw-redirect" title="Side channel" href="https://en.wikipedia.org/wiki/Side_channel">side channel</a> key leaking mechanisms" into the OpenBSD crypto code. In the forwarded email from 2010, Theo de Raadt did not at first express an official position on the validity of the claims, apart from the implicit endorsement from forwarding the email.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-39">[39]</a>Jason Wright's response to the allegations: "Every urban legend is made more real by the inclusion of real names, dates, and times. Gregory Perry's email falls into this category. … I will state clearly that I did not add backdoors to the OpenBSD operating system or the OpenBSD crypto framework (OCF)."<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-40">[40]</a> Some days later, de Raadt commented that "I believe that NETSEC was probably contracted to write backdoors as alleged. … If those were written, I don't believe they made it into our tree."<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-41">[41]</a> This was published before the Snowden leaks.

An alternative explanation put forward by the authors of the <a title="Logjam (computer security)" href="https://en.wikipedia.org/wiki/Logjam_(computer_security)">Logjam attack</a> suggests that the NSA compromised IPsec VPNs by undermining the <a class="mw-redirect" title="Diffie-Hellman" href="https://en.wikipedia.org/wiki/Diffie-Hellman">Diffie-Hellman</a> algorithm used in the key exchange. In their paper<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-42">[42]</a> they allege the NSA specially built a computing cluster to precompute multiplicative subgroups for specific primes and generators, such as for the second Oakley group defined in <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2409" rel="nofollow">RFC 2409</a>. As of May 2015, 90% of addressable IPsec VPNs supported the second Oakley group as part of IKE. If an organization were to precompute this group, they could derive the keys being exchanged and decrypt traffic without inserting any software backdoors.

A second alternative explanation that was put forward was that the <a title="Equation Group" href="https://en.wikipedia.org/wiki/Equation_Group">Equation Group</a> used <a title="Zero-day (computing)" href="https://en.wikipedia.org/wiki/Zero-day_(computing)">zero-day exploits</a> against several manufacturers' VPN equipment which were validated by <a title="Kaspersky Lab" href="https://en.wikipedia.org/wiki/Kaspersky_Lab">Kaspersky Lab</a> as being tied to the Equation Group<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-43">[43]</a> and validated by those manufacturers as being real exploits, some of which were zero-day exploits at the time of their exposure.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-44">[44]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-45">[45]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-46">[46]</a> The <a title="Cisco PIX" href="https://en.wikipedia.org/wiki/Cisco_PIX#Security_vulnerabilities">Cisco PIX and ASA</a> firewalls had vulnerabilities that were used for wiretapping by the NSA.

Furthermore, IPsec VPNs using "Aggressive Mode" settings send a hash of the PSK in the clear. This can be and apparently is targeted by the NSA using offline dictionary attacks.<a href="https://en.wikipedia.org/wiki/IPsec#cite_note-47">[47]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-48">[48]</a><a href="https://en.wikipedia.org/wiki/IPsec#cite_note-49">[49]</a>

<h2>IETF documentation[<a title="Edit section: IETF documentation" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=13">edit</a>]</h2>

<h3>Standards track[<a title="Edit section: Standards track" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=14">edit</a>]</h3>

<ul>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc1829" rel="nofollow">RFC 1829</a>: The ESP DES-CBC Transform</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2403" rel="nofollow">RFC 2403</a>: The Use of HMAC-MD5-96 within ESP and AH</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2404" rel="nofollow">RFC 2404</a>: The Use of HMAC-SHA-1-96 within ESP and AH</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2405" rel="nofollow">RFC 2405</a>: The ESP DES-CBC Cipher Algorithm With Explicit IV</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2410" rel="nofollow">RFC 2410</a>: The NULL Encryption Algorithm and Its Use With IPsec</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2451" rel="nofollow">RFC 2451</a>: The ESP CBC-Mode Cipher Algorithms</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2857" rel="nofollow">RFC 2857</a>: The Use of HMAC-RIPEMD-160-96 within ESP and AH</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc3526" rel="nofollow">RFC 3526</a>: More Modular Exponential (MODP) Diffie-Hellman groups for Internet Key Exchange (IKE)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc3602" rel="nofollow">RFC 3602</a>: The AES-CBC Cipher Algorithm and Its Use with IPsec</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc3686" rel="nofollow">RFC 3686</a>: Using Advanced Encryption Standard (AES) Counter Mode With IPsec Encapsulating Security Payload (ESP)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc3947" rel="nofollow">RFC 3947</a>: Negotiation of NAT-Traversal in the IKE</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc3948" rel="nofollow">RFC 3948</a>: UDP Encapsulation of IPsec ESP Packets</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4106" rel="nofollow">RFC 4106</a>: The Use of Galois/Counter Mode (GCM) in IPsec Encapsulating Security Payload (ESP)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4301" rel="nofollow">RFC 4301</a>: Security Architecture for the Internet Protocol</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4302" rel="nofollow">RFC 4302</a>: IP Authentication Header</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4303" rel="nofollow">RFC 4303</a>: IP Encapsulating Security Payload</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4304" rel="nofollow">RFC 4304</a>: Extended Sequence Number (ESN) Addendum to IPsec Domain of Interpretation (DOI) for Internet Security Association and Key Management Protocol (ISAKMP)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4307" rel="nofollow">RFC 4307</a>: Cryptographic Algorithms for Use in the Internet Key Exchange Version 2 (<a class="mw-redirect" title="IKEv2" href="https://en.wikipedia.org/wiki/IKEv2">IKEv2</a>)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4308" rel="nofollow">RFC 4308</a>: Cryptographic Suites for IPsec</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4309" rel="nofollow">RFC 4309</a>: Using Advanced Encryption Standard (AES) CCM Mode with IPsec Encapsulating Security Payload (ESP)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4543" rel="nofollow">RFC 4543</a>: The Use of Galois Message Authentication Code (GMAC) in IPsec ESP and AH</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4555" rel="nofollow">RFC 4555</a>: IKEv2 Mobility and Multihoming Protocol (MOBIKE)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4806" rel="nofollow">RFC 4806</a>: Online Certificate Status Protocol (OCSP) Extensions to IKEv2</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4868" rel="nofollow">RFC 4868</a>: Using HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512 with IPsec</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4945" rel="nofollow">RFC 4945</a>: The Internet IP Security PKI Profile of IKEv1/ISAKMP, IKEv2, and PKIX</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc5280" rel="nofollow">RFC 5280</a>: Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc5282" rel="nofollow">RFC 5282</a>: Using Authenticated Encryption Algorithms with the Encrypted Payload of the Internet Key Exchange version 2 (IKEv2) Protocol</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc5386" rel="nofollow">RFC 5386</a>: Better-Than-Nothing Security: An Unauthenticated Mode of IPsec</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc5529" rel="nofollow">RFC 5529</a>: Modes of Operation for Camellia for Use with IPsec</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc5685" rel="nofollow">RFC 5685</a>: Redirect Mechanism for the Internet Key Exchange Protocol Version 2 (IKEv2)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc5723" rel="nofollow">RFC 5723</a>: Internet Key Exchange Protocol Version 2 (IKEv2) Session Resumption</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc5857" rel="nofollow">RFC 5857</a>: IKEv2 Extensions to Support Robust Header Compression over IPsec</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc5858" rel="nofollow">RFC 5858</a>: IPsec Extensions to Support Robust Header Compression over IPsec</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc7296" rel="nofollow">RFC 7296</a>: Internet Key Exchange Protocol Version 2 (IKEv2)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc7321" rel="nofollow">RFC 7321</a>: Cryptographic Algorithm Implementation Requirements and Usage Guidance for Encapsulating Security Payload (ESP) and Authentication Header (AH)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc7383" rel="nofollow">RFC 7383</a>: Internet Key Exchange Protocol Version 2 (IKEv2) Message Fragmentation</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc7427" rel="nofollow">RFC 7427</a>: Signature Authentication in the Internet Key Exchange Version 2 (IKEv2)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc7634" rel="nofollow">RFC 7634</a>: ChaCha20, Poly1305, and Their Use in the Internet Key Exchange Protocol (IKE) and IPsec</li>

</ul>

<h3>Experimental RFCs[<a title="Edit section: Experimental RFCs" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=15">edit</a>]</h3>

<ul>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4478" rel="nofollow">RFC 4478</a>: Repeated Authentication in Internet Key Exchange (IKEv2) Protocol</li>

</ul>

<h3>Informational RFCs[<a title="Edit section: Informational RFCs" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=16">edit</a>]</h3>

<ul>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2367" rel="nofollow">RFC 2367</a>: PF_KEY Interface</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2412" rel="nofollow">RFC 2412</a>: The OAKLEY Key Determination Protocol</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc3706" rel="nofollow">RFC 3706</a>: A Traffic-Based Method of Detecting Dead Internet Key Exchange (IKE) Peers</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc3715" rel="nofollow">RFC 3715</a>: IPsec-Network Address Translation (NAT) Compatibility Requirements</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4621" rel="nofollow">RFC 4621</a>: Design of the IKEv2 Mobility and Multihoming (MOBIKE) Protocol</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4809" rel="nofollow">RFC 4809</a>: Requirements for an IPsec Certificate Management Profile</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc5387" rel="nofollow">RFC 5387</a>: Problem and Applicability Statement for Better-Than-Nothing Security (BTNS)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc5856" rel="nofollow">RFC 5856</a>: Integration of Robust Header Compression over IPsec Security Associations</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc5930" rel="nofollow">RFC 5930</a>: Using Advanced Encryption Standard Counter Mode (AES-CTR) with the Internet Key Exchange version 02 (IKEv2) Protocol</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc6027" rel="nofollow">RFC 6027</a>: IPsec Cluster Problem Statement</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc6071" rel="nofollow">RFC 6071</a>: IPsec and IKE Document Roadmap</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc6379" rel="nofollow">RFC 6379</a>: Suite B Cryptographic Suites for IPsec</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc6380" rel="nofollow">RFC 6380</a>: Suite B Profile for Internet Protocol Security (IPsec)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc6467" rel="nofollow">RFC 6467</a>: Secure Password Framework for Internet Key Exchange Version 2 (IKEv2)</li>

</ul>

<h3>Best current practice RFCs[<a title="Edit section: Best current practice RFCs" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=17">edit</a>]</h3>

<ul>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc5406" rel="nofollow">RFC 5406</a>: Guidelines for Specifying the Use of IPsec Version 2</li>

</ul>

<h3>Obsolete/historic RFCs[<a title="Edit section: Obsolete/historic RFCs" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=18">edit</a>]</h3>

<ul>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc1825" rel="nofollow">RFC 1825</a>: Security Architecture for the Internet Protocol (obsoleted by <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2401" rel="nofollow">RFC 2401</a>)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc1826" rel="nofollow">RFC 1826</a>: IP Authentication Header (obsoleted by <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2402" rel="nofollow">RFC 2402</a>)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc1827" rel="nofollow">RFC 1827</a>: IP Encapsulating Security Payload (ESP) (obsoleted by <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2406" rel="nofollow">RFC 2406</a>)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc1828" rel="nofollow">RFC 1828</a>: IP Authentication using Keyed MD5 (historic)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2401" rel="nofollow">RFC 2401</a>: Security Architecture for the Internet Protocol (IPsec overview) (obsoleted by <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4301" rel="nofollow">RFC 4301</a>)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2406" rel="nofollow">RFC 2406</a>: IP Encapsulating Security Payload (ESP) (obsoleted by <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4303" rel="nofollow">RFC 4303</a> and <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4305" rel="nofollow">RFC 4305</a>)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2407" rel="nofollow">RFC 2407</a>: The Internet IP Security Domain of Interpretation for ISAKMP (obsoleted by <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4306" rel="nofollow">RFC 4306</a>)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2409" rel="nofollow">RFC 2409</a>: The Internet Key Exchange (obsoleted by <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4306" rel="nofollow">RFC 4306</a>)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4305" rel="nofollow">RFC 4305</a>: Cryptographic Algorithm Implementation Requirements for Encapsulating Security Payload (ESP) and Authentication Header (AH) (obsoleted by <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4835" rel="nofollow">RFC 4835</a>)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4306" rel="nofollow">RFC 4306</a>: Internet Key Exchange (IKEv2) Protocol (obsoleted by <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc5996" rel="nofollow">RFC 5996</a>)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4718" rel="nofollow">RFC 4718</a>: IKEv2 Clarifications and Implementation Guidelines (obsoleted by <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc7296" rel="nofollow">RFC 7296</a>)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc4835" rel="nofollow">RFC 4835</a>: Cryptographic Algorithm Implementation Requirements for Encapsulating Security Payload (ESP) and Authentication Header (AH) (obsoleted by <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc7321" rel="nofollow">RFC 7321</a>)</li>

<li><a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc5996" rel="nofollow">RFC 5996</a>: Internet Key Exchange Protocol Version 2 (IKEv2) (obsoleted by <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc7296" rel="nofollow">RFC 7296</a>)</li>

</ul>

<ul>

<li><img src="/b2c7126d-7cf3-455f-b111-4e9464b0b44b.png" /><a title="Portal:Cryptography" href="https://en.wikipedia.org/wiki/Portal:Cryptography">Cryptography portal</a></li>

</ul>

</div>

<ul>

<li><a title="Dynamic Multipoint Virtual Private Network" href="https://en.wikipedia.org/wiki/Dynamic_Multipoint_Virtual_Private_Network">Dynamic Multipoint Virtual Private Network</a></li>

<li><a title="Information security" href="https://en.wikipedia.org/wiki/Information_security">Information security</a></li>

<li><a title="NAT traversal" href="https://en.wikipedia.org/wiki/NAT_traversal">NAT traversal</a></li>

<li><a title="Opportunistic encryption" href="https://en.wikipedia.org/wiki/Opportunistic_encryption">Opportunistic encryption</a></li>

<li><a title="Tcpcrypt" href="https://en.wikipedia.org/wiki/Tcpcrypt">tcpcrypt</a></li>

</ul>

<h2>References[<a title="Edit section: References" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=20">edit</a>]</h2>

<li id="cite_note-rfc2406-1">^ <a href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc2406_1-0">Jump up to:a</a> <a href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc2406_1-1">b</a> <a href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc2406_1-2">c</a> <cite class="citation">Kent, S.; Atkinson, R. (November 1998). <a class="external text" href="https://tools.ietf.org/html/rfc2406" rel="nofollow">IP Encapsulating Security Payload (ESP)</a>. <a title="Internet Engineering Task Force" href="https://en.wikipedia.org/wiki/Internet_Engineering_Task_Force">IETF</a>. <a title="Digital object identifier" href="https://en.wikipedia.org/wiki/Digital_object_identifier">doi</a>:<a class="external text" href="https://doi.org/10.17487%2FRFC2406" rel="nofollow">10.17487/RFC2406</a>. RFC 2406.</cite></li>

<li id="cite_note-2"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-2">^{</a> }<cite class="citation web"><a class="external text" href="https://ieeexplore.ieee.org/document/6168355/" rel="nofollow">"Implementation of IPSec Protocol - IEEE Conference Publication"</a>. ieeexplore.ieee.org. Retrieved 2018-05-12.</cite></li>

<li id="cite_note-3"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-3">^{</a> }<a class="external free" href="http://www.toad.com/gnu/netcrypt.html" rel="nofollow">http://www.toad.com/gnu/netcrypt.html</a></li>

<li id="cite_note-4"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-4">^{</a> }<cite class="citation web"><a class="external text" href="https://www.le-vpn.com/history-of-vpn/" rel="nofollow">"The history of VPN creation"</a>.</cite></li>

<li id="cite_note-5"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-5">^{</a> }<cite class="citation web"><a class="external text" href="https://datatracker.ietf.org/wg/ipsec/history/" rel="nofollow">"IETF IP Security Protocol (ipsec) Working group History"</a>.</cite></li>

<li id="cite_note-6"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-6">^{</a> }<cite class="citation web"><a class="external text" href="http://tools.ietf.org/html/rfc4301#page-4" rel="nofollow">"RFC4301: Security Architecture for the Internet Protocol"</a>. Network Working Group of the IETF. December 2005. p. 4. <q>The spelling "IPsec" is preferred and used throughout this and all related IPsec standards. All other capitalizations of IPsec [...] are deprecated.</q></cite></li>

<li id="cite_note-7"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-7">^{</a> }<cite class="citation web"><a class="external text" href="https://www.nrl.navy.mil/itd/sites/www.nrl.navy.mil.itd/files/files/itd_accomp_ipsec.pdf" rel="nofollow">"NRL ITD Accomplishments - IPSec and IPv6"</a> (PDF). US Naval Research Laboratories.</cite></li>

<li id="cite_note-rfc2411-8"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc2411_8-0">^{</a> }<cite class="citation">Thayer, R.; Doraswamy, N.; Glenn, R. (November 1998). <a class="external text" href="https://tools.ietf.org/html/rfc2411" rel="nofollow">IP Security Document Roadmap</a>. <a title="Internet Engineering Task Force" href="https://en.wikipedia.org/wiki/Internet_Engineering_Task_Force">IETF</a>. <a title="Digital object identifier" href="https://en.wikipedia.org/wiki/Digital_object_identifier">doi</a>:<a class="external text" href="https://doi.org/10.17487%2FRFC2411" rel="nofollow">10.17487/RFC2411</a>. RFC 2411.</cite></li>

<li id="cite_note-rfc4308-9"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc4308_9-0">^{</a> }<cite class="citation">Hoffman, P. (December 2005). <a class="external text" href="https://tools.ietf.org/html/rfc4308" rel="nofollow">Cryptographic Suites for IPsec</a>. <a title="Internet Engineering Task Force" href="https://en.wikipedia.org/wiki/Internet_Engineering_Task_Force">IETF</a>. <a title="Digital object identifier" href="https://en.wikipedia.org/wiki/Digital_object_identifier">doi</a>:<a class="external text" href="https://doi.org/10.17487%2FRFC4308" rel="nofollow">10.17487/RFC4308</a>. RFC 4308.</cite></li>

<li id="cite_note-rfc2402-10">^ <a href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc2402_10-0">Jump up to:a</a> <a href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc2402_10-1">b</a> <cite class="citation">Kent, S.; Atkinson, R. (November 1998). <a class="external text" href="https://tools.ietf.org/html/rfc2402" rel="nofollow">IP Authentication Header</a>. <a title="Internet Engineering Task Force" href="https://en.wikipedia.org/wiki/Internet_Engineering_Task_Force">IETF</a>. <a title="Digital object identifier" href="https://en.wikipedia.org/wiki/Digital_object_identifier">doi</a>:<a class="external text" href="https://doi.org/10.17487%2FRFC2402" rel="nofollow">10.17487/RFC2402</a>. RFC 2402.</cite></li>

<li id="cite_note-rfc4302-11">^ <a href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc4302_11-0">Jump up to:a</a> <a href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc4302_11-1">b</a> <a href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc4302_11-2">c</a> <a href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc4302_11-3">d</a> <a href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc4302_11-4">e</a> <cite class="citation">Kent, S. (December 2005). <a class="external text" href="https://tools.ietf.org/html/rfc4302" rel="nofollow">IP Authentication Header</a>. <a title="Internet Engineering Task Force" href="https://en.wikipedia.org/wiki/Internet_Engineering_Task_Force">IETF</a>. <a title="Digital object identifier" href="https://en.wikipedia.org/wiki/Digital_object_identifier">doi</a>:<a class="external text" href="https://doi.org/10.17487%2FRFC4302" rel="nofollow">10.17487/RFC4302</a>. RFC 4302.</cite></li>

<li id="cite_note-rfc2409_sec1-12"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc2409_sec1_12-0">^{</a> }The <a title="Internet Key Exchange" href="https://en.wikipedia.org/wiki/Internet_Key_Exchange">Internet Key Exchange</a> (IKE), <a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2409" rel="nofollow">RFC 2409</a>, §1 Abstract</li>

<li id="cite_note-rfc2409-13"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc2409_13-0">^{</a> }<cite class="citation">Harkins, D.; Carrel, D. (November 1998). <a class="external text" href="https://tools.ietf.org/html/rfc2409" rel="nofollow">The Internet Key Exchange (IKE)</a>. <a title="Internet Engineering Task Force" href="https://en.wikipedia.org/wiki/Internet_Engineering_Task_Force">IETF</a>. <a title="Digital object identifier" href="https://en.wikipedia.org/wiki/Digital_object_identifier">doi</a>:<a class="external text" href="https://doi.org/10.17487%2FRFC2409" rel="nofollow">10.17487/RFC2409</a>. RFC 2409.</cite></li>

<li id="cite_note-rfc4306-14"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc4306_14-0">^{</a> }<cite class="citation">Kaufman, C. (ed.). <a class="external text" href="https://tools.ietf.org/html/rfc4306" rel="nofollow">IKE Version 2</a>. <a title="Internet Engineering Task Force" href="https://en.wikipedia.org/wiki/Internet_Engineering_Task_Force">IETF</a>. <a title="Digital object identifier" href="https://en.wikipedia.org/wiki/Digital_object_identifier">doi</a>:<a class="external text" href="https://doi.org/10.17487%2FRFC4306" rel="nofollow">10.17487/RFC4306</a>. RFC 4306.</cite></li>

<li id="cite_note-rfc4430-15"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc4430_15-0">^{</a> }<cite class="citation">Sakane, S.; Kamada, K.; Thomas, M.; Vilhuber, J. (November 1998). <a class="external text" href="https://tools.ietf.org/html/rfc4430" rel="nofollow">Kerberized Internet Negotiation of Keys (KINK)</a>. <a title="Internet Engineering Task Force" href="https://en.wikipedia.org/wiki/Internet_Engineering_Task_Force">IETF</a>. <a title="Digital object identifier" href="https://en.wikipedia.org/wiki/Digital_object_identifier">doi</a>:<a class="external text" href="https://doi.org/10.17487%2FRFC4430" rel="nofollow">10.17487/RFC4430</a>. RFC 4430.</cite></li>

<li id="cite_note-RFC_4025-16">^ <a href="https://en.wikipedia.org/wiki/IPsec#cite_ref-RFC_4025_16-0">Jump up to:a</a> <a href="https://en.wikipedia.org/wiki/IPsec#cite_ref-RFC_4025_16-1">b</a> <cite class="citation">Richardson, M. (February 2005). <a class="external text" href="https://tools.ietf.org/html/rfc4025" rel="nofollow">A Method for Storing IPsec Keying Material in DNS</a>. <a title="Internet Engineering Task Force" href="https://en.wikipedia.org/wiki/Internet_Engineering_Task_Force">IETF</a>. <a title="Digital object identifier" href="https://en.wikipedia.org/wiki/Digital_object_identifier">doi</a>:<a class="external text" href="https://doi.org/10.17487%2FRFC4025" rel="nofollow">10.17487/RFC4025</a>. RFC 4025.</cite></li>

<li id="cite_note-17"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-17">^{</a> }<cite class="citation book">Peter Willis (2001). Carrier-Scale IP Networks: Designing and Operating Internet Networks. IET. p. 270. <a title="International Standard Book Number" href="https://en.wikipedia.org/wiki/International_Standard_Book_Number">ISBN</a> <a title="Special:BookSources/9780852969823" href="https://en.wikipedia.org/wiki/Special:BookSources/9780852969823"><bdi>9780852969823</bdi></a>.</cite></li>

<li id="cite_note-iana-18">^ <a href="https://en.wikipedia.org/wiki/IPsec#cite_ref-iana_18-0">Jump up to:a</a> <a href="https://en.wikipedia.org/wiki/IPsec#cite_ref-iana_18-1">b</a> <cite class="citation web"><a class="external text" href="https://www.webcitation.org/5rXTFZt87?url=http://www.iana.org/assignments/protocol-numbers/protocol-numbers.xml" rel="nofollow">"Protocol Numbers"</a>. IANA. <a title="Internet Assigned Numbers Authority" href="https://en.wikipedia.org/wiki/Internet_Assigned_Numbers_Authority">IANA</a>. 2010-05-27. Archived from <a class="external text" href="http://www.iana.org/assignments/protocol-numbers/protocol-numbers.xml" rel="nofollow">the original</a> on 2010-07-27.</cite></li>

<li id="cite_note-19"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-19">^{</a> }<cite class="citation web"><a class="external text" href="http://www.toad.com/gnu/draft-ietf-sip-esp-00.txt" rel="nofollow">"SIPP Encapsulating Security Payload"</a>. IETF SIPP Working Group. 1993.</cite></li>

<li id="cite_note-20"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-20">^{</a> }<cite class="citation web"><a class="external text" href="http://tools.ietf.org/html/draft-ietf-sipp-spec-00" rel="nofollow">"Draft SIPP Specification"</a>. IETF. 1993. p. 21.</cite></li>

<li id="cite_note-21"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-21">^{</a> }<cite class="citation conference"><a title="Steven M. Bellovin" href="https://en.wikipedia.org/wiki/Steven_M._Bellovin">Bellovin, Steven M.</a> (1996). <a class="external text" href="http://www.cs.columbia.edu/_{smb/papers/badesp.ps}" rel="nofollow">"Problem Areas for the IP Security Protocols"</a> (<a title="PostScript" href="https://en.wikipedia.org/wiki/PostScript">PostScript</a>). Proceedings of the Sixth Usenix Unix Security Symposium. San Jose, CA. pp. 1–16. Retrieved 2007-07-09.</cite></li>

<li id="cite_note-22"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-22">^{</a> }<cite class="citation conference">Paterson, Kenneth G.; Yau, Arnold K.L. (2006-04-24). <a class="external text" href="http://eprint.iacr.org/2005/416" rel="nofollow">"Cryptography in theory and practice: The case of encryption in IPsec"</a> (PDF). Eurocrypt 2006, Lecture Notes in Computer Science Vol. 4004. Berlin. pp. 12–29. Retrieved 2007-08-13.</cite></li>

<li id="cite_note-23"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-23">^{</a> }<cite class="citation conference">Degabriele, Jean Paul; Paterson, Kenneth G. (2007-08-09). <a class="external text" href="http://eprint.iacr.org/2007/125" rel="nofollow">"Attacking the IPsec Standards in Encryption-only Configurations"</a> (PDF). IEEE Symposium on Security and Privacy, IEEE Computer Society. Oakland, CA. pp. 335–349. Retrieved 2007-08-13.</cite></li>

<li id="cite_note-rfc4303-24"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc4303_24-0">^{</a> }<cite class="citation">Kent, S. (December 2005). <a class="external text" href="https://tools.ietf.org/html/rfc4303" rel="nofollow">IP Encapsulating Security Payload (ESP)</a>. <a title="Internet Engineering Task Force" href="https://en.wikipedia.org/wiki/Internet_Engineering_Task_Force">IETF</a>. <a title="Digital object identifier" href="https://en.wikipedia.org/wiki/Digital_object_identifier">doi</a>:<a class="external text" href="https://doi.org/10.17487%2FRFC4303" rel="nofollow">10.17487/RFC4303</a>. RFC 4303.</cite></li>

<li id="cite_note-25"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-25">^{</a> }<cite class="citation book">Peter Willis (2001). Carrier-Scale IP Networks: Designing and Operating Internet Networks. IET. p. 271. <a title="International Standard Book Number" href="https://en.wikipedia.org/wiki/International_Standard_Book_Number">ISBN</a> <a title="Special:BookSources/9780852969823" href="https://en.wikipedia.org/wiki/Special:BookSources/9780852969823"><bdi>9780852969823</bdi></a>.</cite></li>

<li id="cite_note-26"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-26">^{</a> }<cite class="citation book">Peter Willis (2001). Carrier-Scale IP Networks: Designing and Operating Internet Networks. IET. pp. 272–3. <a title="International Standard Book Number" href="https://en.wikipedia.org/wiki/International_Standard_Book_Number">ISBN</a> <a title="Special:BookSources/9780852969823" href="https://en.wikipedia.org/wiki/Special:BookSources/9780852969823"><bdi>9780852969823</bdi></a>.</cite></li>

<li id="cite_note-28"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-28">^{</a> }<cite class="citation">Thomas, M. (June 2001). <a class="external text" href="https://tools.ietf.org/html/rfc3129" rel="nofollow">Requirements for Kerberized Internet Negotiation of Keys</a>. <a title="Digital object identifier" href="https://en.wikipedia.org/wiki/Digital_object_identifier">doi</a>:<a class="external text" href="https://doi.org/10.17487%2FRFC3129" rel="nofollow">10.17487/RFC3129</a>. RFC 3129.</cite></li>

<li id="cite_note-29"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-29">^{</a> }William, S., & Stallings, W. (2006). Cryptography and Network Security, 4/E. Pearson Education India. p. 492-493</li>

<li id="cite_note-30"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-30">^{</a> }<cite class="citation book">Peter Willis (2001). Carrier-Scale IP Networks: Designing and Operating Internet Networks. IET. p. 266. <a title="International Standard Book Number" href="https://en.wikipedia.org/wiki/International_Standard_Book_Number">ISBN</a> <a title="Special:BookSources/9780852969823" href="https://en.wikipedia.org/wiki/Special:BookSources/9780852969823"><bdi>9780852969823</bdi></a>.</cite></li>

<li id="cite_note-31"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-31">^{</a> }<cite class="citation book">Peter Willis (2001). Carrier-Scale IP Networks: Designing and Operating Internet Networks. IET. p. 267. <a title="International Standard Book Number" href="https://en.wikipedia.org/wiki/International_Standard_Book_Number">ISBN</a> <a title="Special:BookSources/9780852969823" href="https://en.wikipedia.org/wiki/Special:BookSources/9780852969823"><bdi>9780852969823</bdi></a>.</cite></li>

<li id="cite_note-rfc2367-32"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc2367_32-0">^{</a> }<a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc2367" rel="nofollow">RFC 2367</a>, PF_KEYv2 Key Management API, Dan McDonald, Bao Phan, & Craig Metz (July 1998)</li>

<li id="cite_note-33"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-33">^{</a> }<cite class="citation book">Hamad, Mohammad; Prevelakis, Vassilis (2015). Implementation and performance evaluation of embedded IPsec in microkernel OS. 2015 World Symposium on Computer Networks and Information Security (WSCNIS). IEEE. <a title="Digital object identifier" href="https://en.wikipedia.org/wiki/Digital_object_identifier">doi</a>:<a class="external text" href="https://doi.org/10.1109%2Fwscnis.2015.7368294" rel="nofollow">10.1109/wscnis.2015.7368294</a>. <a title="International Standard Book Number" href="https://en.wikipedia.org/wiki/International_Standard_Book_Number">ISBN</a> <a title="Special:BookSources/9781479999064" href="https://en.wikipedia.org/wiki/Special:BookSources/9781479999064"><bdi>9781479999064</bdi></a>.</cite></li>

<li id="cite_note-rfc6434-34"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-rfc6434_34-0">^{</a> }<a class="external mw-magiclink-rfc" href="https://tools.ietf.org/html/rfc6434" rel="nofollow">RFC 6434</a>, "IPv6 Node Requirements", E. Jankiewicz, J. Loughney, T. Narten (December 2011)</li>

<li id="cite_note-35"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-35">^{</a> }<cite class="citation web"><a class="external text" href="https://datatracker.ietf.org/wg/ipsecme/charter/" rel="nofollow">"ipsecme charter"</a>. Retrieved 2015-10-26.</cite></li>

<li id="cite_note-36"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-36">^{</a> }<cite class="citation web"><a class="external text" href="https://tools.ietf.org/wg/ipsecme/" rel="nofollow">"ipsecme status"</a>. Retrieved 2015-10-26.</cite></li>

<li id="cite_note-37"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-37">^{</a> }<cite class="citation web"><a class="external text" href="https://www.nytimes.com/interactive/2013/09/05/us/documents-reveal-nsa-campaign-against-encryption.html" rel="nofollow">"Secret Documents Reveal N.S.A. Campaign Against Encryption"</a>. New York Times.</cite></li>

<li id="cite_note-gilmore_bullrun-38"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-gilmore_bullrun_38-0">^{</a> }<cite class="citation web">John Gilmore. <a class="external text" href="http://www.mail-archive.com/cryptography@metzdowd.com/msg12325.html" rel="nofollow">"Re: [Cryptography] Opening Discussion: Speculation on "BULLRUN""</a>.</cite></li>

<li id="cite_note-39"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-39">^{</a> }<cite class="citation web">Theo de Raadt. <a class="external text" href="http://marc.info/?l=openbsd-tech&m=129236621626462&w=2" rel="nofollow">"Allegations regarding OpenBSD IPSEC"</a>.</cite></li>

<li id="cite_note-40"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-40">^{</a> }<cite class="citation web">Jason Wright. <a class="external text" href="http://marc.info/?l=openbsd-tech&m=129244045916861&w=2" rel="nofollow">"Allegations regarding OpenBSD IPSEC"</a>.</cite></li>

<li id="cite_note-41"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-41">^{</a> }<cite class="citation web">Theo de Raadt. <a class="external text" href="https://lwn.net/Articles/420858/" rel="nofollow">"Update on the OpenBSD IPSEC backdoor allegation"</a>.</cite></li>

<li id="cite_note-42"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-42">^{</a> }<cite class="citation web">David Adrian; Karthikeyan Bhargavan; Zakir Durumeric; Pierrick Gaudry; Matthew Green; <a class="mw-redirect" title="J. Alex Halderman" href="https://en.wikipedia.org/wiki/J._Alex_Halderman">J. Alex Halderman</a>; <a title="Nadia Heninger" href="https://en.wikipedia.org/wiki/Nadia_Heninger">Nadia Heninger</a>; Drew Springall; Emmanuel Thomé; Luke Valenta; Benjamin VanderSloot; Eric Wustrow; Santiago Zanella-Béguelink; Paul Zimmermann. <a class="external text" href="https://weakdh.org/imperfect-forward-secrecy.pdf" rel="nofollow">"Imperfect Forward Secrecy: How Diffie-Hellman Fails in Practice"</a> (PDF).</cite></li>

<li id="cite_note-43"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-43">^{</a> }<cite class="citation news">Goodin, Dan (August 16, 2016). <a class="external text" href="https://arstechnica.com/security/2016/08/code-dumped-online-came-from-omnipotent-nsa-tied-hacking-group/" rel="nofollow">"Confirmed: hacking tool leak came from "omnipotent" NSA-tied group"</a>. Ars Technica. Retrieved August 19, 2016.</cite></li>

<li id="cite_note-44"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-44">^{</a> }<cite class="citation news">Thomson, Iain (August 17, 2016). <a class="external text" href="https://www.theregister.co.uk/2016/08/17/cisco_two_shadow_brokers_vulnerabilities_real/" rel="nofollow">"Cisco confirms two of the Shadow Brokers' 'NSA' vulns are real"</a>. <a title="The Register" href="https://en.wikipedia.org/wiki/The_Register">The Register</a>. Retrieved September 16,2016.</cite></li>

<li id="cite_note-45"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-45">^{</a> }<cite class="citation news">Pauli, Darren (August 24, 2016). <a class="external text" href="https://www.theregister.co.uk/2016/08/24/equation_group_exploit_expanded_to_target_cisco_924_asa_boxes/" rel="nofollow">"Equation Group exploit hits newer Cisco ASA, Juniper Netscreen"</a>. <a title="The Register" href="https://en.wikipedia.org/wiki/The_Register">The Register</a>. Retrieved September 16, 2016.</cite></li>

<li id="cite_note-46"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-46">^{</a> }<cite class="citation news">Chirgwin, Richard (August 18, 2016). <a class="external text" href="https://www.theregister.co.uk/2016/08/18/fortinet_follows_cisco_in_confirming_shadow_broker_vuln/" rel="nofollow">"Fortinet follows Cisco in confirming Shadow Broker vuln"</a>. <a title="The Register" href="https://en.wikipedia.org/wiki/The_Register">The Register</a>. Retrieved September 16, 2016.</cite></li>

<li id="cite_note-47"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-47">^{</a> }<a class="external free" href="https://weakdh.org/imperfect-forward-secrecy-ccs15.pdf" rel="nofollow">https://weakdh.org/imperfect-forward-secrecy-ccs15.pdf</a></li>

<li id="cite_note-48"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-48">^{</a> }<a class="external free" href="http://crypto.stackexchange.com/questions/27404/what-are-the-problems-of-ikev1-aggressive-mode-compared-to-ikev1-main-mode-or-i" rel="nofollow">http://crypto.stackexchange.com/questions/27404/what-are-the-problems-of-ikev1-aggressive-mode-compared-to-ikev1-main-mode-or-i</a></li>

<li id="cite_note-49"><a title="Jump up" href="https://en.wikipedia.org/wiki/IPsec#cite_ref-49">^{</a> }<a class="external free" href="https://nohats.ca/wordpress/blog/2014/12/29/dont-stop-using-ipsec-just-yet/" rel="nofollow">https://nohats.ca/wordpress/blog/2014/12/29/dont-stop-using-ipsec-just-yet/</a></li>

</ol>

</div>

<h2>External links[<a title="Edit section: External links" href="https://en.wikipedia.org/w/index.php?title=IPsec&action=edit&section=21">edit</a>]</h2>

<ul>

<li>&lsaquo;The <a title="Help:Template" href="https://en.wikipedia.org/wiki/Help:Template">template</a> <a title="Template:Curlie" href="https://en.wikipedia.org/wiki/Template:Curlie">Curlie</a> is being <a title="Wikipedia:Templates for discussion/Log/2019 May 6" href="https://en.wikipedia.org/wiki/Wikipedia:Templates_for_discussion/Log/2019_May_6#Template:Curlie">considered for deletion</a>.&rsaquo; <a class="external text" href="https://curlie.org/Computers/Security/" rel="nofollow">Computer Security</a> at <a class="mw-redirect" title="Curlie" href="https://en.wikipedia.org/wiki/Curlie">Curlie</a></li>

<li><a class="external text" href="http://www.ietf.org/html.charters/wg-dir.html#Security%20Area" rel="nofollow">All IETF active security WGs</a>

<ul>

<li><a class="external text" href="http://datatracker.ietf.org/wg/ipsecme/" rel="nofollow">IETF ipsecme WG</a> ("IP Security Maintenance and Extensions" Working Group)</li>

<li><a class="external text" href="https://web.archive.org/web/20070416135452/http://www.ietf.org/html.charters/btns-charter.html" rel="nofollow">IETF btns WG</a> ("Better-Than-Nothing Security" Working Group) (chartered to work on unauthenticated IPsec, IPsec APIs, connection latching)]</li>

</ul>

</li>

<li><a class="external text" href="http://www.windowsecurity.com/articles/Securing_Data_in_Transit_with_IPSec.html" rel="nofollow">Securing Data in Transit with IPsec</a> WindowsSecurity.com article by Deb Shinder</li>

<li><a class="external text" href="http://www.microsoft.com/ipsec" rel="nofollow">IPsec</a> on Microsoft TechNet

<ul>

<li><a class="external text" href="http://www.microsoft.com/downloads/details.aspx?FamilyID=1d4c292c-7998-42e4-8786-789c7b457881&displaylang=en" rel="nofollow">Microsoft IPsec Diagnostic Tool</a> on Microsoft Download Center</li>

</ul>

</li>

<li><a class="external text" href="http://www.unixwiz.net/techtips/iguide-ipsec.html" rel="nofollow">An Illustrated Guide to IPsec</a> by Steve Friedl</li>

<li><a class="external text" href="https://www.ict.tuwien.ac.at/lva/384.081/infobase/P97-IPsec_v4-7.pdf" rel="nofollow">Security Architecture for IP (IPsec)</a> Data Communication Lectures by Manfred Lindner Part IPsec</li>

<li><a class="external text" href="http://www.linuxjournal.com/article/9916" rel="nofollow">Creating VPNs with IPsec and SSL/TLS</a> Linux Journal article by Rami Rosen</li>

</ul>

<tbody>

<tr>

<ul>

</ul>

</div>

<div id="Virtual_private_networking"><a title="Virtual private network" href="https://en.wikipedia.org/wiki/Virtual_private_network">Virtual private networking</a></div>

</th>

</tr>

<tr>

<th class="navbox-group" scope="row"><a class="mw-redirect" title="Communications protocol" href="https://en.wikipedia.org/wiki/Communications_protocol">Communications protocol</a></th>

<div>

<ul>

<li><a class="mw-selflink selflink">IPsec</a></li>

<li><a title="Split tunneling" href="https://en.wikipedia.org/wiki/Split_tunneling">Split tunneling</a></li>

<li>(<a title="Opportunistic encryption" href="https://en.wikipedia.org/wiki/Opportunistic_encryption">Opportunistic</a>: <a title="Tcpcrypt" href="https://en.wikipedia.org/wiki/Tcpcrypt">tcpcrypt</a>)</li>

</ul>

</div>

</td>

</tr>

<tr>

<th class="navbox-group" scope="row"><a title="Free software" href="https://en.wikipedia.org/wiki/Free_software">Free software</a></th>

<div>

<ul>

<li><a title="Cloudvpn" href="https://en.wikipedia.org/wiki/Cloudvpn">Cloudvpn</a></li>

<li><a title="FreeLAN" href="https://en.wikipedia.org/wiki/FreeLAN">FreeLAN</a></li>

<li><a title="FreeS/WAN" href="https://en.wikipedia.org/wiki/FreeS/WAN">FreeS/WAN</a></li>

<li><a title="Libreswan" href="https://en.wikipedia.org/wiki/Libreswan">Libreswan</a></li>

<li><a title="OpenConnect" href="https://en.wikipedia.org/wiki/OpenConnect">OpenConnect</a></li>

<li><a title="OpenIKED" href="https://en.wikipedia.org/wiki/OpenIKED">OpenIKED</a></li>

<li><a title="Openswan" href="https://en.wikipedia.org/wiki/Openswan">Openswan</a></li>

<li><a title="OpenVPN" href="https://en.wikipedia.org/wiki/OpenVPN">OpenVPN</a></li>

<li><a title="Social VPN" href="https://en.wikipedia.org/wiki/Social_VPN">Social VPN</a></li>

<li><a title="SoftEther VPN" href="https://en.wikipedia.org/wiki/SoftEther_VPN">SoftEther VPN</a></li>

<li><a title="StrongSwan" href="https://en.wikipedia.org/wiki/StrongSwan">strongSwan</a></li>

<li><a title="Tcpcrypt" href="https://en.wikipedia.org/wiki/Tcpcrypt">tcpcrypt</a></li>

<li><a title="WireGuard" href="https://en.wikipedia.org/wiki/WireGuard">WireGuard</a></li>

<li><a title="Shadowsocks" href="https://en.wikipedia.org/wiki/Shadowsocks">Shadowsocks</a></li>

</ul>

</div>

</td>

</tr>

<tr>

<th class="navbox-group" scope="row">Vendor-driven protocols</th>

<div>

<ul>

<li><a title="Layer 2 Forwarding Protocol" href="https://en.wikipedia.org/wiki/Layer_2_Forwarding_Protocol">Layer 2 Forwarding Protocol</a></li>

<li><a title="DirectAccess" href="https://en.wikipedia.org/wiki/DirectAccess">DirectAccess</a></li>

</ul>

</div>

</td>

</tr>

<tr>

<th class="navbox-group" scope="row"><a title="Proprietary software" href="https://en.wikipedia.org/wiki/Proprietary_software">Proprietary software</a></th>

<div>

<ul>

<li><a title="Avast SecureLine VPN" href="https://en.wikipedia.org/wiki/Avast_SecureLine_VPN">Avast SecureLine VPN</a></li>

<li><a title="Check Point VPN-1" href="https://en.wikipedia.org/wiki/Check_Point_VPN-1">Check Point VPN-1</a></li>

<li><a title="Cisco Systems VPN Client" href="https://en.wikipedia.org/wiki/Cisco_Systems_VPN_Client">Cisco Systems VPN Client</a></li>

<li><a title="LogMeIn Hamachi" href="https://en.wikipedia.org/wiki/LogMeIn_Hamachi">LogMeIn Hamachi</a></li>

<li><a title="Microsoft Forefront Unified Access Gateway" href="https://en.wikipedia.org/wiki/Microsoft_Forefront_Unified_Access_Gateway">Microsoft Forefront Unified Access Gateway</a></li>

<li><a class="mw-redirect" title="Tunnelbear" href="https://en.wikipedia.org/wiki/Tunnelbear">Tunnelbear</a></li>

<li><a title="NordVPN" href="https://en.wikipedia.org/wiki/NordVPN">NordVPN</a></li>

<li><a title="SaferVPN" href="https://en.wikipedia.org/wiki/SaferVPN">SaferVPN</a></li>

<li><a title="ExpressVPN" href="https://en.wikipedia.org/wiki/ExpressVPN">ExpressVPN</a></li>

<li><a title="ProtonVPN" href="https://en.wikipedia.org/wiki/ProtonVPN">ProtonVPN</a></li>

<li><a title="PureVPN" href="https://en.wikipedia.org/wiki/PureVPN">PureVPN</a></li>

<li><a title="Private Internet Access" href="https://en.wikipedia.org/wiki/Private_Internet_Access">Private Internet Access</a></li>

<li><a title="AzireVPN" href="https://en.wikipedia.org/wiki/AzireVPN">AzireVPN</a></li>

<li><a title="AceVPN" href="https://en.wikipedia.org/wiki/AceVPN">AceVPN</a></li>

</ul>

</div>

</td>

</tr>

<tr>

<th class="navbox-group" scope="row">Risk Vectors</th>

<div>

<ul>

<li><a title="Content-control software" href="https://en.wikipedia.org/wiki/Content-control_software">Content-control software</a></li>

<li><a title="Deep content inspection" href="https://en.wikipedia.org/wiki/Deep_content_inspection">Deep content inspection</a></li>

<li><a title="Deep packet inspection" href="https://en.wikipedia.org/wiki/Deep_packet_inspection">Deep packet inspection</a></li>

<li><a title="IP address blocking" href="https://en.wikipedia.org/wiki/IP_address_blocking">IP address blocking</a></li>

<li><a title="Network enumeration" href="https://en.wikipedia.org/wiki/Network_enumeration">Network enumeration</a></li>

<li><a title="Stateful firewall" href="https://en.wikipedia.org/wiki/Stateful_firewall">Stateful firewall</a></li>

<li><a title="TCP reset attack" href="https://en.wikipedia.org/wiki/TCP_reset_attack">TCP Reset</a></li>

<li><a title="VPN blocking" href="https://en.wikipedia.org/wiki/VPN_blocking">VPN blocking</a></li>

</ul>

</div>

</td>

</tr>

</tbody>

</table>

</div>

<tbody>

<tr>

<th id="Authority_control_frameless&#124;text-top&#124;10px&#124;alt=Edit_this_at_Wikidata&#124;link=https&#58;//www.wikidata.org/wiki/Q210214&#124;Edit_this_at_Wikidata" class="navbox-group" scope="row"><a title="Help:Authority control" href="https://en.wikipedia.org/wiki/Help:Authority_control">Authority control</a> <img src="/1cb9cba4-13b8-550f-90fe-4cdabf5d09fc.png" /></th>

<div>

<ul>

</ul>

</div>

</td>

</tr>

</tbody>

</table>

</div>

<div id="mw-normal-catlinks" class="mw-normal-catlinks"><a title="Help:Category" href="https://en.wikipedia.org/wiki/Help:Category">Categories</a>:

<ul>

<li><a title="Category:IPsec" href="https://en.wikipedia.org/wiki/Category:IPsec">IPsec</a></li>

<li><a title="Category:Internet protocols" href="https://en.wikipedia.org/wiki/Category:Internet_protocols">Internet protocols</a></li>

<li><a title="Category:Cryptographic protocols" href="https://en.wikipedia.org/wiki/Category:Cryptographic_protocols">Cryptographic protocols</a></li>

<li><a title="Category:Tunneling protocols" href="https://en.wikipedia.org/wiki/Category:Tunneling_protocols">Tunneling protocols</a></li>

<li><a title="Category:Network layer protocols" href="https://en.wikipedia.org/wiki/Category:Network_layer_protocols">Network layer protocols</a></li>

</ul>

</div>

IPsec

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