XMPP E2E Security
This page aims to provide an overview, comparison and evaluation of existing and proposed end-to-end security solutions for XMPP, after providing the characteristings of the XMPP setting with regard to communication and the security of it.
Proposals
XEP-0384: OMEMO Encryption (Signal / Text Secure)
Recommendation: Implement.
OMEMO is based on the Signal double ratchet and provides forward secrecy, compatibility with history retrieval for devices that are already part of the ratchet, and a number of other benefits over legacy encryption mechanisms. It has had an independent third party audit (see related links at bottom).
XEP-0027 (legacy PGP)
Recommendation: implement only if compatibility with legacy clients is required.
One of the first proposals for end-to-end security is based on PGP and described in XEP-0027.
The way XEP-0027 uses PGP, it doesn't provide protection from replay attacks. It also only encrypts messages and doesn't sign them, so they could be replaced with different correctly encrypted messages on the wire.(Source: chat in xsf@m.x.o) Thus it has been obsoleted by the XMPP Council in it's meeting on 2014-03-12.
OTR (Off-the-record Messaging)
Recommendation: implement only if compatibility with legacy clients is required.
OTR is a crypto protocol, specifically designed to secure instant messaging conversations. Its usage in XMPP is documented (but not standardized) in https://xmpp.org/extensions/xep-0364.html
Comparative Overview
| Proposal | Security property | Communication patterns | Compatibility with XMPP | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Authenticity | Integrity | Encryption | Forward secrecy | Malleable encryption | One-to-One | Groupchat | Online chats | Offline messages | Multiple resources | Discovery of support | |
| OMEMO (XEP-0384) | ? | ? | Yes | Yes | ? | Yes | Yes (with limitations) | Yes | Yes | Yes | Yes |
| Legacy PGP (XEP-0027) | No (messages only encrypted, not signed) | No | Yes | No | N/A | Yes | No | Yes | Yes | Yes (if same keypair at all resources) | No |
| OTR | Yes | Yes | Yes | Yes | Yes | Yes | No | Yes | No | No | No |
Related Documents
- https://developer.pidgin.im/wiki/EndToEndXMPPCrypto
- http://trevp.net/talk_2014_04_02.pdf
- https://conversations.im/omemo/audit.pdf
Discussion
If you have any questions or comments regarding this page, please join the XSF chatroom at xsf@muc.xmpp.org.