"This document describes how to prepare Unicode strings representing user names and passwords for comparison. The document defines the ""SASLprep"" profile of the ""stringprep"" algorithm to be used for both user names and passwords. This profile is intended to be used by Simple Authentication and Security Layer (SASL) mechanisms (such as PLAIN@ CRAM-MD5@ and DIGEST-MD5)@ as well as other protocols exchanging simple user names and/or passwords."
RFC 4013-2005 history
2005RFC 4013-2005 SASLprep: Stringprep Profile for User Names and Passwords