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'''LRD''' can stand for:
'''IPsec (IP security)''' is a standard for securing [[Internet Protocol]] (IP) communications by [[encryption|encrypting]] and/or [[authentication|authenticating]] all IP packets. IPsec provides security at the [[network layer]].
*The [[Labour Research Department]], a United Kingdom trade union based research organisation
IPsec is set of [[cryptographic protocol]]s for (1) securing packet flows and (2) [[key exchange]]. Of the former, there are two: '''Encapsulating Security Payload (ESP)''' provides [[authentication]], data [[confidentiality]] and [[message integrity]]; '''Authentication Header (AH)''' provides authentication and message integrity, but does not offer confidentiality. Originally AH was only used for integrity and ESP was used only for encryption; authentication functionality was added subsequently to ESP. Currently only one [[Key-agreement protocol|key exchange]] protocol is defined, the [[Internet key exchange|IKE]] (Internet Key Exchange) protocol.
*The [[ISO 4217]] code for the [[Liberian dollar]]
*[[Les Rythmes Digitales]]
{{TLAdisambig}}
==Current status as a standard==
IPsec is an obligatory part of [[IPv6]], the new [[IETF]] Internet standard for [[Internet Protocol]] (IP) packet traffic, and is optional for use with [[IPv4]]. As a result, IPsec is expected to become more widely deployed as IPv6 becomes more popular. IPsec protocols are defined by [[Request for Comments|RFC]]s 2401-2412. [[As of 2004]], work is progressing to release updated replacement documents.
==Design intent==
IPsec was intended to provide either (1) ''tunnel mode'': portal-to-portal [[communications security]] in which security of packet traffic is provided to several machines (even to whole [[LAN]]s) by a single node, or (2) ''transport mode'': end-to-end security of packet traffic in which the end-point computers do the security processing. It can be used to construct [[Virtual Private Network]]s (VPN) in either mode, and this is the dominant use. Note, however, that the security implications are quite different between the two operational modes.
End-to-end communication security on an Internet-wide scale has been slower to develop than many had expected. Part of the reason is that no universal, or universally trusted, [[Public Key Infrastructure]] (PKI) has emerged ([[DNSSEC]] was originally envisioned for this), part is that many users understand neither their needs nor the available options well enough to force inclusion in vendors' products (which would lead to widespread adoption), and part is probably due to degradation (or anticipated degradation) of [[lag|Net responsivity]] due to bandwidth loss from such things as [[spamming|spam]].
==IPsec compared to other Internet security protocols==
IPsec protocols operate at layer 3 of the [[OSI model]], which makes them suitable for protecting both [[Transmission Control Protocol|TCP]] and [[User Datagram Protocol|UDP]]-based protocols when used alone. This means that, compared with transport layer and above protocols such as [[Secure Sockets Layer|SSL]] (OSI Layer 6), which cannot protect UDP level traffic, the IPsec protocols must cope with reliability and fragmentation issues, adding their complexity and processing overhead. [[Transport Layer Security|SSL/TLS]], in contrast, rely on a higher level layer [[Transmission Control Protocol|TCP]] (OSI Layer 4) to manage reliability and fragmentation.
== Technical details ==
=== Authentication Header ===
Authentication Header (AH) is intended to guarantee connectionless integrity and data origin authentication of IP datagrams. Further, it can optionally protect against [[replay attack]]s by using the [[sliding window]] technique and discarding old packets. AH tries to protect all fields of an IP datagram. Only fields changeable during transfer of an IP packet are excluded.
An AH packet diagram:
{| border="1" cellspacing="0" cellpadding="2px"
| style="text-align:left;" | 0
| style="text-align:left;" | 1
| style="text-align:left;" | 2
| style="text-align:left;" | 3
|--
| 0 1 2 3 4 5 6 7
| 0 1 2 3 4 5 6 7
| 0 1 2 3 4 5 6 7
| 0 1 2 3 4 5 6 7
|--
| style="text-align:center;" | Next Header
| style="text-align:center;" | Payload Length
| colspan="2" style="text-align:center;" | RESERVED
|--
| colspan="4" style="text-align:center;" | Security Parameters Index (SPI)
|--
| colspan="4" style="text-align:center;" | Sequence Number
|--
| colspan="4" style="text-align:center;" |
Authentication Data (variable)
|}
Field meanings:
; Next Header : Identifies the protocol of the transferred data.
; Payload Length : Size of AH packet.
; RESERVED : Reserved for future use (all zero until then).
; Security Parameters Index (SPI) : Identifies the security parameters in combination with IP address.
; Sequence Number : A monotonically increasing number, used to prevent replay attacks.
; Authentication Data : Contains the data necessary to authenticate the packet.
=== Encapsulated Security Payload (ESP) ===
The Encapsulating Security Payload (ESP) extension header provides origin authenticity, integrity, and confidentiality of a packet. Unlike the AH header, the IP packet header is not accounted for.
An ESP packet diagram:
{| border="1" cellspacing="0" cellpadding="2px"
| style="text-align:left;" colspan="8" | 0
| style="text-align:left;" colspan="8" | 1
| style="text-align:left;" colspan="8" | 2
| style="text-align:left;" colspan="8" | 3
|--
| 0 || 1 || 2 || 3 || 4 || 5 || 6 || 7
| 0 || 1 || 2 || 3 || 4 || 5 || 6 || 7
| 0 || 1 || 2 || 3 || 4 || 5 || 6 || 7
| 0 || 1 || 2 || 3 || 4 || 5 || 6 || 7
|--
| colspan="32" style="text-align:center;" | Security Parameters Index (SPI)
|--
| colspan="32" style="text-align:center;" | Sequence Number
|--
| colspan="32" style="text-align:center;border-bottom:none;" |
Payload * (variable)
|--
| style="border-top:none;" colspan="8" |
| colspan="24" style="text-align:center;border-bottom:none;" | Padding (0-255 bytes)
|--
| style="border-right:none;" colspan="8" |
| style="border-left:none;border-top:none;" colspan="8" |
| style="text-align:center;" colspan="8" | Pad Length
| style="text-align:center;" colspan="8" | Next Header
|--
| colspan="32" style="text-align:center;" |
Authentication Data (variable)
|}
Field meanings:
; Security Parameters Index (SPI) : Identifies the security parameters in combination with IP address
; Sequence Number : A monotonically increasing number, used to prevent replay attacks.
; Payload Data : The data to be transferred.
; Padding : Used with some block ciphers to pad the data to the full length of a block.
; Pad Length : Size of padding in bits.
; Next Header : Identifies the protocol of the transferred data.
; Authentication Data : Contains the data used to authenticate the packet.
== Implementations ==
IPsec support is usually implemented in the [[kernel (computer science)|kernel]] with key management and [[ISAKMP]]/[[IKE]] negotiation carried out from user-space. Existing IPsec implementations tend to include both of these functionalities. However, as there is a standard interface for key management, it is possible to control one kernel IPsec stack using key management tools from a different implementation.
Because of this, there is confusion as to the origins of the IPsec implementation that is in the [[Linux kernel]]. The [[FreeS/WAN]] project made the first complete and [[open source]] implementation of IPsec for [[Linux]]. It consists of a kernel IPsec stack ([[KLIPS]]), as well as a key management [[daemon (computer software)|daemon]] ([[pluto (openswan)|pluto]]). The FreeS/WAN project was disbanded in [[March 2004]]. [[Openswan]] and [[strongSwan]] are continuations of FreeS/WAN. The [[KAME]] project also implemented complete IPsec support for [[NetBSD]], [[FreeBSD]], as well as [[Linux]]. Its key management daemon is called [[racoon (kame)|racoon]].
However, none of these kernel IPsec stacks were integrated into the Linux kernel. [[Alexey Kuznetsov]] and [[David S. Miller]] wrote a kernel IPsec implementation from scratch for the Linux kernel around the end of 2002. This stack was subsequently released as part of Linux 2.6.
Therefore, contrary to popular belief, the Linux IPsec stack did not originate from the KAME project. As it supports the standard [[PFKEY]] protocol and the native [[XFRM]] interface for key management, the Linux IPsec stack can be used in conjunction with either pluto from Openswan or racoon from the [[KAME]] project.
There are a number of implementations of '''IPsec''' and ISAKMP/IKE protocols. These include:
* [[NRL IPsec]], one of the original
* [[OpenBSD]], with its own code derived from NRL IPsec
* [[Mac OS X]], which includes the KAME IPsec code
* [[Cisco Systems|Cisco]] [[IOS]]
* [[Microsoft Windows]] Win2K and WinXP
* [[SSH Sentinel]] (now part of [[SafeNet]]) provides toolkits
* [[Solaris Operating Environment|Solaris]]
* [[IBM]] [[AIX operating system]]
* [[IBM]] [[z/OS]]
==See also==
* [[Information security]]
== Overview of IPsec Related RFCs ==
; RFC 2401: Security Architecture for the Internet Protocol
; RFC 2402: Authentication Header
; RFC 2406: Encapsulating Security Payload
; RFC 2407: IPsec Domain of Interpretation for ISAKMP (IPsec DoI)
; RFC 2408: Internet Security Association and Key Management Protocol (ISAKMP)
; RFC 2409: Internet Key Exchange (IKE)
; RFC 2410: The NULL Encryption Algorithm and Its Use With IPsec
; RFC 2411: IP Security Document Roadmap
; RFC 2412: The OAKLEY Key Determination Protocol
== External links ==
* [http://www.ietf.org/html.charters/OLD/ipsec-charter.html IETF IPsec WG has "concluded", archive of the page is here]
* [https://datatracker.ietf.org/public/idindex.cgi?command=show_wg_id&id=1091 IPsec WG still has important active drafts]
* [http://www.ietf.org/html.charters/wg-dir.html#Security%20Area All IETF active security WGs]
* [http://www.windowsecurity.com/articles/Securing_Data_in_Transit_with_IPSec.html Securing Data in Transit with IPSec]
* [http://www.freeswan.org/ Free S/WAN project homepage].
* [http://www.openswan.org/ Openswan project homepage].
* [http://www.strongswan.org/ strongSwan project homepage].
* [http://www.vpnc.org/ The VPN Consortium].
* [http://www.netsys.com/ipsec/2000/msg00777.html A long thread on the ipsec@lists.tislabs.com] about whether uppercasing the S or not. The RFCs indicate that it is spelled "IPsec".
* [http://www.unixwiz.net/techtips/iguide-ipsec.html An Illustrated Guide to IPSec]
[[Category:Internet protocols]]
[[Category:Cryptographic protocols]]
[[Category:Tunneling protocols]]
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[[it:IPsec]]
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[[ru:IPSEC]]
[[fi:IPsec]]
[[zh:安全IP]]
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