PRECIS

Application protocols using Unicode code points in protocol strings need to properly handle such strings in order to enforce internationalization rules for strings placed in various protocol slots (such as addresses and identifiers) and to perform valid comparison operations (e.g., for purposes of authentication or authorization). This document defines a framework enabling application protocols to perform the preparation, enforcement, and comparison of internationalized strings ("PRECIS") in a way that depends on the properties of Unicode code points and thus is more agile with respect to versions of Unicode. As a result, this framework provides a more sustainable approach to the handling of internationalized strings than the previous framework, known as Stringprep (RFC 3454). This document obsoletes RFC 7564.

This document describes updated methods for handling Unicode strings representing usernames and passwords. The previous approach was known as SASLprep (RFC 4013) and was based on Stringprep (RFC 3454). The methods specified in this document provide a more sustainable approach to the handling of internationalized usernames and passwords. This document obsoletes RFC 7613.

This document describes methods for handling Unicode strings representing memorable, human-friendly names (called "nicknames", "display names", or "petnames") for people, devices, accounts, websites, and other entities. This document obsoletes RFC 7700.

The framework for the preparation, enforcement, and comparison of internationalized strings (PRECIS) defines several classes of strings for use in application protocols. Because many protocols perform case-sensitive or case-insensitive string comparison, it is necessary to define methods for case mapping. In addition, both the Internationalized Domain Names in Applications (IDNA) and the PRECIS problem statement describe mappings for internationalized strings that are not limited to case, but include width mapping and mapping of delimiters and other special characters that can be taken into consideration. This document provides guidelines for designers of PRECIS profiles and describes several mappings that can be applied between receiving user input and passing permitted code points to internationalized protocols. In particular, this document describes both locale-dependent and context-depending case mappings as well as additional mappings for delimiters and special characters.

This document defines the address format for the Extensible Messaging and Presence Protocol (XMPP), including support for code points outside the ASCII range. This document obsoletes RFC 6122.

If a protocol expects to compare two strings and is prepared only for those strings to be ASCII, then using Unicode code points in those strings requires they be prepared somehow. Internationalizing Domain Names in Applications (here called IDNA2003) defined and used Stringprep and Nameprep. Other protocols subsequently defined Stringprep profiles. A new approach different from Stringprep and Nameprep is used for a revision of IDNA2003 (called IDNA2008). Other Stringprep profiles need to be similarly updated, or a replacement of Stringprep needs to be designed. This document outlines the issues to be faced by those designing a Stringprep replacement.