Initial version approved by the Council.
The Off-the-Record messaging protocol (OTR) is widely layered on top of XMPP to provide end-to-end encryption. Current use of the protocol is described in &xep0364;. OTR provides its own discovery mechanism in which it sends messages with special whitespace characters to indicate support. While this works when initializing a session, there is no way to query a client for support and to know in advance that a particular version of OTR is supported. This specification aims to solve that by providing an in-band mechanism for discovering OTR support in XMPP.
It should be noted that newer, more secure encryption protocols exist for XMPP, and that new implementations of OTR are discouraged. This protocol is primarily intended to solve issues with existing implementations of OTR.
If an entity supports OTR it MUST advertise the fact by returning a feature of 'urn:xmpp:otr:0' &VNOTE; in response to a &xep0030; information request. This indicates support for OTRv3 as defined by &otr3;.
If older versions of OTR are required, they may be discovered out of band using OTRs built in mechanism which is beyond the scope of this document.
Because OTR support is advertised outside of any end-to-end encrypted stream, it may be subject to downgrade attacks (eg. the server operator may remove OTR from the features list).
This document requires no interaction with the Internet Assigned Numbers Authority (IANA).
This specification defines the following XML namespaces:
The ®ISTRAR; shall include the foregoing namespaces in its disco features registry as defined in &xep0030;.
urn:xmpp:otr:0
Indicates support for Off-the-Record Messaging (OTR) version 3
XEP-0378
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