Added reference to Simplified Encrypted Session Negotiation
End-to-end encryption is a desirable feature for any communication technology. Ideally, such a technology would design encryption in from the beginning and would forbid unencrypted communications. Realistically, most communication technologies have not been designed in that manner, and Jabber/XMPP technologies are no exception. In particular, the original Jabber technologies developed in 1999 did not include end-to-end encryption by default. PGP-based encryption of message bodies and signing of presence information was added as an extension to the core protocols in the year 2000; this extension is documented in &xep0027;. When the core protocols were formalized within the Internet Standards Process by the IETF's XMPP Working Group in 2003 (see &rfc3920; and &rfc3921;), a different extension was defined using S/MIME-based signing and encryption of CPIM-formatted messages (see &rfc3862;) and PIDF-formatted presence information (see &rfc3863;); this extension is specified in &rfc3923;.
-For reasons described in &xep0188;, the foregoing proposals (and others not mentioned) have not been widely implemented and deployed. This is unfortunate, since an open communication protocol needs to enable end-to-end encryption in order to be seriously considered for deployment by a broad range of users.
-This document describes a different session-based approach to the end-to-end encryption of the full content of XMPP stanzas sent between two entities. The protocol assumes that the encrypted session parameters (initial keys, counters and algorithms etc.) have already been agreed, typically through a negotiation protocol such as &xep0116; or &xep0187;. The session approach when combined with short-lived keys offers many important advantages over the existing "Object Encryption" proposals, including Perfect Forward Secrecy.
+For reasons described in &xep0210;, the foregoing proposals (and others not mentioned) have not been widely implemented and deployed. This is unfortunate, since an open communication protocol needs to enable end-to-end encryption in order to be seriously considered for deployment by a broad range of users.
+This document describes a different session-based approach to the end-to-end encryption of the full content of XMPP stanzas sent between two entities. The protocol assumes that the encrypted session parameters (initial keys, counters and algorithms etc.) have already been agreed, typically through a negotiation protocol such as &xep0116;, &xep0217; or &xep0187;. The session approach when combined with short-lived keys offers many important advantages over the existing "Object Encryption" proposals, including Perfect Forward Secrecy and Identity Protection.