# Authenticated Identity Body

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**Authenticated Identity Body (AIB)** is a mechanism used in the [Session Initiation Protocol](/source/Session_Initiation_Protocol) (**SIP**) to verify the [identity](/source/Digital_identity) of the [sender](/source/Sending) of a [message](/source/Message). It allows communicating parties in a [network](/source/Telecommunications_network) to exchange *authenticated identity information*, improving the [security](/source/Network_security) and [integrity](/source/Data_integrity) of SIP communications such as [Voice over IP](/source/Voice_over_IP) (VoIP) calls.

An AIB works by embedding a [digitally signed section](/source/Digital_signature) inside a SIP message. The sender signs specific SIP [headers](/source/Header_(computing)) such as From, To, or Call-ID to prove that the message genuinely originates from the claimed identity. Additional [headers](/source/Header_(computing)), such as Date or Contact, may also be included in the signed data to protect against [replay attacks](/source/Replay_attack) and maintain [reference](/source/Reference_(computer_science)) integrity.

AIBs build upon existing [authentication](/source/Authentication) methods like [S/MIME](/source/S/MIME), but are designed to be more narrowly focused on [verifying](/source/Verification_and_validation) message origin and preventing identity [spoofing](/source/Spoofing_attack) in SIP [environments](/source/Open_system_(systems_theory)).

The specification for Authenticated Identity Bodies is defined in [RFC 3893](/source/RFC_3893). According to the document, AIBs may optionally be [encrypted](/source/Encryption) to protect [end-to-end](/source/End-to-end_principle) privacy. In such cases, encryption should occur before the AIB is [signed](/source/Digital_signature). The security of the encrypted AIB depends on proper [key distribution](/source/Key_distribution) among trusted [hosts](/source/Host_(network)), which may be practical in controlled networks (for example, within [telephone providers](/source/Telecommunications_company) or [federations](/source/Federation) of trusted systems).[1]

## See also

- [Session Initiation Protocol](/source/Session_Initiation_Protocol)
- [Encryption](/source/Encryption)
- [Cryptography](/source/Cryptography)

## References

1. Peterson, Jon (2004). [*Session Initiation Protocol (SIP) Authenticated Identity Body (AIB) Format*](https://datatracker.ietf.org/doc/rfc3893/). No. RFC 3893. Internet Engineering Task Force. [doi:10.17487/rfc3893](https://doi.org/10.17487/rfc3893)

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Adapted from the Wikipedia article [Authenticated Identity Body](https://en.wikipedia.org/wiki/Authenticated_Identity_Body) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Authenticated_Identity_Body?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.