< draft-melnikov-precis-saslprepbis-03.txt		draft-melnikov-precis-saslprepbis-04.txt >
	Precis P. Saint-Andre		Precis P. Saint-Andre
	Internet-Draft Cisco Systems, Inc.		Internet-Draft Cisco Systems, Inc.
	Obsoletes: 4013 (if approved) A. Melnikov		Obsoletes: 4013 (if approved) A. Melnikov
	Intended status: Standards Track Isode Ltd		Intended status: Standards Track Isode Ltd
	Expires: March 18, 2013 September 14, 2012		Expires: March 27, 2013 September 23, 2012
	Preparation and Comparison of Internationalized Strings Representing		Preparation and Comparison of Internationalized Strings Representing
	Simple User Names and Passwords		Simple User Names and Passwords
	draft-melnikov-precis-saslprepbis-03		draft-melnikov-precis-saslprepbis-04
	Abstract		Abstract
	This document describes how to handle Unicode strings representing		This document describes how to handle Unicode strings representing
	simple user names and passwords, primarily for purposes of		simple user names and passwords, primarily for purposes of
	comparison. This profile is intended to be used by Simple		comparison. This profile is intended to be used by Simple
	Authentication and Security Layer (SASL) mechanisms (such as PLAIN		Authentication and Security Layer (SASL) mechanisms (such as PLAIN
	and SCRAM-SHA-1), as well as other protocols that exchange simple		and SCRAM-SHA-1), as well as other protocols that exchange simple
	user names or passwords. This document obsoletes RFC 4013.		user names or passwords. This document obsoletes RFC 4013.
	skipping to change at page 1, line 37 ¶		skipping to change at page 1, line 37 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on March 18, 2013.		This Internet-Draft will expire on March 27, 2013.
	Copyright Notice		Copyright Notice
	Copyright (c) 2012 IETF Trust and the persons identified as the		Copyright (c) 2012 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 2, line 16 ¶		skipping to change at page 2, line 16 ¶
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
	1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3		1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3
	1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3		1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Simple User Names . . . . . . . . . . . . . . . . . . . . . . 4		2. Simple User Names . . . . . . . . . . . . . . . . . . . . . . 4
	2.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 4		2.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 4
	2.2. Preparation . . . . . . . . . . . . . . . . . . . . . . . 4		2.2. Preparation . . . . . . . . . . . . . . . . . . . . . . . 4
	2.3. Migration . . . . . . . . . . . . . . . . . . . . . . . . 5		3. Passwords . . . . . . . . . . . . . . . . . . . . . . . . . . 5
	3. Passwords . . . . . . . . . . . . . . . . . . . . . . . . . . 6		3.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 5
	3.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 6		3.2. Preparation . . . . . . . . . . . . . . . . . . . . . . . 5
	3.2. Preparation . . . . . . . . . . . . . . . . . . . . . . . 6		4. Migration . . . . . . . . . . . . . . . . . . . . . . . . . . 6
	3.3. Migration . . . . . . . . . . . . . . . . . . . . . . . . 7		4.1. User Names . . . . . . . . . . . . . . . . . . . . . . . . 6
	4. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 8		4.2. Passwords . . . . . . . . . . . . . . . . . . . . . . . . 7
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 8		5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
	5.1. Password/Passphrase Strength . . . . . . . . . . . . . . . 8		5.1. Password/Passphrase Strength . . . . . . . . . . . . . . . 8
	5.2. Reuse of PRECIS . . . . . . . . . . . . . . . . . . . . . 8		5.2. Reuse of PRECIS . . . . . . . . . . . . . . . . . . . . . 8
	5.3. Reuse of Unicode . . . . . . . . . . . . . . . . . . . . . 8		5.3. Reuse of Unicode . . . . . . . . . . . . . . . . . . . . . 9
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8		6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
	6.1. Use of NameClass . . . . . . . . . . . . . . . . . . . . . 8		6.1. Use of NameClass . . . . . . . . . . . . . . . . . . . . . 9
	6.2. Use of FreeClass . . . . . . . . . . . . . . . . . . . . . 9		6.2. Use of FreeClass . . . . . . . . . . . . . . . . . . . . . 9
	7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9		7. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 9
	7.1. Normative References . . . . . . . . . . . . . . . . . . . 9		8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
	7.2. Informative References . . . . . . . . . . . . . . . . . . 9		8.1. Normative References . . . . . . . . . . . . . . . . . . . 10
	Appendix A. Differences from RFC 4013 . . . . . . . . . . . . . . 10		8.2. Informative References . . . . . . . . . . . . . . . . . . 10
			Appendix A. Differences from RFC 4013 . . . . . . . . . . . . . . 11
	Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 11		Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 11
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
	1. Introduction		1. Introduction
	1.1. Overview		1.1. Overview
	User names and passwords are used pervasively in authentication and		User names and passwords are used pervasively in authentication and
	authorization on the Internet. To increase the likelihood that the		authorization on the Internet. To increase the likelihood that the
	input and comparison of user names and passwords will work in ways		input and comparison of user names and passwords will work in ways
	that make sense for typical users throughout the world, this document		that make sense for typical users throughout the world, this document
	defines rules for preparing and comparing internationalized strings		defines rules for preparing and comparing internationalized strings
	skipping to change at page 3, line 25 ¶		skipping to change at page 3, line 25 ¶
	The algorithms defined in this document assume that all strings are		The algorithms defined in this document assume that all strings are
	comprised of characters from the Unicode character set [UNICODE].		comprised of characters from the Unicode character set [UNICODE].
	The algorithms are designed for use in Simple Authentication and		The algorithms are designed for use in Simple Authentication and
	Security Layer (SASL) [RFC4422] mechanisms, such as PLAIN [RFC4616]		Security Layer (SASL) [RFC4422] mechanisms, such as PLAIN [RFC4616]
	and SCRAM-SHA-1 [RFC5802]. However, they might be applicable		and SCRAM-SHA-1 [RFC5802]. However, they might be applicable
	wherever simple user names or passwords are used. This profile is		wherever simple user names or passwords are used. This profile is
	not intended for use in preparing strings that are not simple user		not intended for use in preparing strings that are not simple user
	names (e.g., email addresses, DNS domain names, LDAP distinguished		names (e.g., email addresses, DNS domain names, LDAP distinguished
	names), nor in cases where identifiers or secrets are not character		names), nor in cases where identifiers or secrets are not strings
	data (e.g., keys) or require different handling (e.g., case folding).		(e.g., keys or certificates) or require different handling (e.g.,
			case folding).
	This document builds upon the PRECIS framework defined in		This document builds upon the PRECIS framework defined in
	[FRAMEWORK], which differs fundamentally from the stringprep		[FRAMEWORK], which differs fundamentally from the stringprep
	technology [RFC3454] used in SASLprep [RFC4013]. The primary		technology [RFC3454] used in SASLprep [RFC4013]. The primary
	difference is that stringprep profiles allowed all characters except		difference is that stringprep profiles allowed all characters except
	those which were explicitly disallowed, whereas PRECIS profiles		those which were explicitly disallowed, whereas PRECIS profiles
	disallow all characters except those which are explicitly allowed		disallow all characters except those which are explicitly allowed
	(this "inclusion model" was originally used for internationalized		(this "inclusion model" was originally used for internationalized
	domain names in [RFC5891]; see [RFC5894] for further discussion). It		domain names in [RFC5891]; see [RFC5894] for further discussion). It
	is important to keep this distinction in mind when comparing the		is important to keep this distinction in mind when comparing the
	technology defined in this document to SASLprep [RFC4013].		technology defined in this document to SASLprep [RFC4013].
	This document obsoletes RFC 4013.		This document obsoletes RFC 4013.
	1.2. Terminology		1.2. Terminology
	Many important terms used in this document are defined in		Many important terms used in this document are defined in
	[FRAMEWORK], [RFC4422], [RFC5890], [RFC6365], and [UNICODE]. The		[FRAMEWORK], [RFC4422], [RFC5890], [RFC6365], and [UNICODE]. The
	term "non-ASCII" space refers to any Unicode code point with a		term "non-ASCII space" refers to any Unicode code point with a
	general category of "Zs", with the exception of U+0020 (here called		general category of "Zs", with the exception of U+0020 (here called
	"ASCII space").		"ASCII space").
	As used here, the term "password" is not literally limited to a word;		As used here, the term "password" is not literally limited to a word;
	i.e., a password could be a passphrase consisting of more than one		i.e., a password could be a passphrase consisting of more than one
	word, perhaps separated by spaces or other such characters.		word, perhaps separated by spaces or other such characters.
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in		"OPTIONAL" in this document are to be interpreted as described in
	skipping to change at page 4, line 24 ¶		skipping to change at page 4, line 24 ¶
	Some SASL mechanisms (e.g., CRAM-MD5, DIGEST-MD5, and SCRAM) specify		Some SASL mechanisms (e.g., CRAM-MD5, DIGEST-MD5, and SCRAM) specify
	that the authentication identity used in the context of such		that the authentication identity used in the context of such
	mechanisms is a "simple user name" (see Section 2 of [RFC4422] as		mechanisms is a "simple user name" (see Section 2 of [RFC4422] as
	well as [RFC4013]). However, the exact form of a simple user name in		well as [RFC4013]). However, the exact form of a simple user name in
	any particular mechanism or deployment thereof is a local matter, and		any particular mechanism or deployment thereof is a local matter, and
	a simple user name does not necessarily map to an application		a simple user name does not necessarily map to an application
	identifier such as the localpart of an email address.		identifier such as the localpart of an email address.
	For purposes of preparation and comparison of authentication		For purposes of preparation and comparison of authentication
	identities, this document specifies that a simple user name is a		identities, this document specifies that a simple user name is a
	string of [UNICODE] code points, encoded using UTF-8 [RFC3629], and		string of Unicode code points [UNICODE], encoded using UTF-8
	structured as an ordered sequence of "simpleparts" (where the		[RFC3629], and structured as an ordered sequence of "simpleparts"
	complete simple user name can consist of a single simplepart or a		(where the complete simple user name can consist of a single
	space-separated sequence of simpleparts).		simplepart or a space-separated sequence of simpleparts).
	Therefore the syntax for a simple user name is defined as follows		Therefore the syntax for a simple user name is defined as follows
	using the Augmented Backus-Naur Form (ABNF) as specified in		using the Augmented Backus-Naur Form (ABNF) as specified in
	[RFC5234].		[RFC5234].
	simpleusername = simplepart [1*(1*SP simplepart)]		simpleusername = simplepart [1*(1*SP simplepart)]
	simplepart = 1*(namepoint)		simplepart = 1*(namepoint)
	;		;
	; a "namepoint" is a UTF-8 encoded		; a "namepoint" is a UTF-8 encoded
	; Unicode code point that conforms to		; Unicode code point that conforms to
	; the "NameClass" string class defined		; the "NameClass" string class defined
	; in draft-ietf-precis-framework		; in draft-ietf-precis-framework
	;		;
			Note well that all code points and blocks not explicitly allowed in
			the PRECIS NameClass are disallowed; this includes private use
			characters, surrogate code points, and the other code points and
			blocks defined as "Prohibited Output" in Section 2.3 of RFC 4013.
	2.2. Preparation		2.2. Preparation
	A simple user name MUST NOT be zero bytes in length. This rule is to		A simple user name MUST NOT be zero bytes in length. This rule is to
	be enforced after any normalization or mapping of code points.		be enforced after any normalization and mapping of code points.
	Each simplepart of a simple user name MUST be treated as follows,
	where the operations specified MUST be completed in the order shown:
	1. Apply Unicode Normalization Form C (NFC) to all characters.		Each simplepart of a simple user name MUST conform to the definition
			of the PRECIS NameClass provided in [FRAMEWORK], where the
			normalization, casemapping, and directionality rules are as described
			below.
	2. Map uppercase and titlecase characters to their lowercase		1. Unicode Normalization Form C (NFC) MUST be applied to all
	equivalents.		characters.
	3. Optionally apply additional mappings, such as those defined in		2. Uppercase and titlecase characters MUST be mapped to their
	[MAPPINGS].		lowercase equivalents.
	4. Ensure that the resulting string conforms to the definition of		3. Additional mappings MAY be applied, such as those defined in
	the PRECIS NameClass.		[I-D.yoneya-precis-mappings].
	With regard to directionality, the "Bidi Rule" provided in [RFC5893]		With regard to directionality, the "Bidi Rule" provided in [RFC5893]
	applies.		applies.
	2.3. Migration
	The rules defined in the previous section differ slightly from those
	defined by the SASLprep specification [RFC4013]. Therefore,
	deployments that currently use SASLprep for handling user names will
	need to scrub existing data when migrating to use of the rules
	defined here. In particular:
	o SASLprep specified the use of Unicode Normalization Form KC
	(NFKC), whereas this usage of the PRECIS NameClass employs Unicode
	Normalization Form C (NFC). In practice this change is unlikely
	to cause significant problems, because NFKC provides methods for
	mapping Unicode code points with compatibility equivalents to
	those equivalents, whereas the PRECIS NameClass entirely disallows
	Unicode code points with compatibility equivalents. For migration
	purposes, deployments need to search their simple user names for
	Unicode code points with compatibility equivalents and map those
	code points to their compatibility equivalents.
	o SASLprep mapped non-ASCII spaces to ASCII space (U+0020), whereas
	the PRECIS NameClass entirely disallows non-ASCII spaces. For
	migration purposes, deployments need to convert non-ASCII space
	characters to ASCII space in simple user names.
	o SASLprep mapped the "characters commonly mapped to nothing" from
	Appendix B.1 of [RFC3454]) to nothing, whereas the PRECIS
	NameClass entirely disallows such characters, which correspond to
	the code points from the "M" category defined under Section 6.13
	of [FRAMEWORK] (with the exception of U+1806 MONGOLIAN TODO SOFT
	HYPHEN, which was commonly mapped to nothing in Unicode 3.2 but at
	the time of this writing is allowed by Unicode 6.1). For
	migration purposes, deployments need to remove code points from
	the PRECIS "M" category in simple user names.
	o SASLprep allowed uppercase and titlecase characters, whereas this
	usage of the PRECIS NameClass maps uppercase and titlecase
	characters to their lowercase equivalents. For migration
	purposes, deployments can either convert uppercase and titlecase
	characters to their lowercase equivalents in simple user names
	(thus losing the case information) or preserve uppercase and
	titlecase characters and ignore the case difference when comparing
	simple user names.
	Note well that all code points and blocks not explicitly allowed in
	the PRECIS NameClass are disallowed; this includes private use
	characters, surrogate code points, and the other code points and
	blocks defined as "Prohibited Output" in Section 2.3 of RFC 4013.
	3. Passwords		3. Passwords
	3.1. Definition		3.1. Definition
	For purposes of preparation and comparison of passwords, this		For purposes of preparation and comparison of passwords, this
	document specifies that a password is a string of [UNICODE] code		document specifies that a password is a string of Unicode code points
	points, encoded using UTF-8 [RFC3629], and conformant to the PRECIS		[UNICODE], encoded using UTF-8 [RFC3629], and conformant to the
	FreeClass.		PRECIS FreeClass.
	Therefore the syntax for a password is defined as follows using the		Therefore the syntax for a password is defined as follows using the
	Augmented Backus-Naur Form (ABNF) as specified in [RFC5234].		Augmented Backus-Naur Form (ABNF) as specified in [RFC5234].
	password = 1*(freepoint)		password = 1*(freepoint)
	;		;
	; a "freepoint" is a UTF-8 encoded		; a "freepoint" is a UTF-8 encoded
	; Unicode code point that conforms to		; Unicode code point that conforms to
	; the "FreeClass" string class defined		; the "FreeClass" string class defined
	; in draft-ietf-precis-framework		; in draft-ietf-precis-framework
	;		;
			Note well that all code points and blocks not explicitly allowed in
			the PRECIS FreeClass are disallowed; this includes private use
			characters, surrogate code points, and the other code points and
			blocks defined as "Prohibited Output" in Section 2.3 of RFC 4013.
	3.2. Preparation		3.2. Preparation
	A password MUST NOT be zero bytes in length. This rule is to be		A password MUST NOT be zero bytes in length. This rule is to be
	enforced after any normalization or mapping of code points.		enforced after any normalization and mapping of code points.
	A password MUST be treated as follows, where the operations specified		A password MUST be treated as follows, where the operations specified
	MUST be completed in the order shown:		MUST be completed in the order shown:
	1. Apply Unicode Normalization Form C (NFC) to all characters.		1. Apply Unicode Normalization Form C (NFC) to all characters.
	2. Map any instances of non-ASCII space to ASCII space (U+0020).		2. Map any instances of non-ASCII space to ASCII space (U+0020).
	3. Ensure that the resulting string conforms to the definition of		3. Ensure that the resulting string conforms to the definition of
	the PRECIS FreeClass.		the PRECIS FreeClass.
	skipping to change at page 7, line 21 ¶		skipping to change at page 6, line 26 ¶
	and similar rules are unnecessary and inapplicable to passwords,		and similar rules are unnecessary and inapplicable to passwords,
	since they can reduce the range of characters that are allowed in a		since they can reduce the range of characters that are allowed in a
	string and therefore reduce the amount of entropy that is possible in		string and therefore reduce the amount of entropy that is possible in
	a password. Furthermore, such rules are intended to minimize the		a password. Furthermore, such rules are intended to minimize the
	possibility that the same string will be displayed differently on a		possibility that the same string will be displayed differently on a
	system set for right-to-left display and a system set for left-to-		system set for right-to-left display and a system set for left-to-
	right display; however, passwords are typically not displayed at all		right display; however, passwords are typically not displayed at all
	and are rarely meant to be interoperable across different systems in		and are rarely meant to be interoperable across different systems in
	the way that non-secret strings like domain names and user names are.		the way that non-secret strings like domain names and user names are.
	3.3. Migration		4. Migration
	The rules defined in the previous section differ slightly from those		The rules defined in this specification differ slightly from those
	defined by the SASLprep specification [RFC4013]. Depending on local		defined by the SASLprep specification [RFC4013]. The following
	service policy, migration from RFC 4013 to this specification might		sections describe these differences, along with their implications
	not involve any scrubbing of data (since passwords might not be		for migration, in more detail.
	stored in the clear anyway); however, service providers need to be
	aware of possible issues that might arise during migration. In		4.1. User Names
	particular:
			Deployments that currently use SASLprep for handling user names might
			need to scrub existing data when migrating to use of the rules
			defined in this specification. In particular:
			o SASLprep specified the use of Unicode Normalization Form KC
			(NFKC), whereas this usage of the PRECIS NameClass employs Unicode
			Normalization Form C (NFC). In practice this change is unlikely
			to cause significant problems, because NFKC provides methods for
			mapping Unicode code points with compatibility equivalents to
			those equivalents, whereas the PRECIS NameClass entirely disallows
			Unicode code points with compatibility equivalents (i.e., during
			comparison NFKC is more "aggressive" about finding matches than is
			NFC). A few examples might suffice to indicate the nature of the
			problem: (1) U+017F LATIN SMALL LETTER LONG S is compatibility
			equivalent to U+0073 LATIN SMALL LETTER S (2) U+2163 ROMAN NUMERAL
			FOUR is compatibility equivalent to U+0049 LATIN CAPITAL LETTER I
			and U+0056 LATIN CAPITAL LETTER V (3) U+FB01 LATIN SMALL LIGATURE
			FI is compatibility equivalent to U+0066 LATIN SMALL LETTER F and
			U+0069 LATIN SMALL LETTER I. Under SASLprep, the use of NFKC also
			handled the mapping of fullwidth and halfwidth code points to
			their decomposition equivalents (see
			[I-D.yoneya-precis-mappings]). Although it is expected that code
			points with compatibility equivalents are rare in existing user
			names, for migration purposes deployments might want to search
			their database of user names for Unicode code points with
			compatibility equivalents and map those code points to their
			compatibility equivalents.
			o SASLprep mapped non-ASCII spaces to ASCII space (U+0020), whereas
			the PRECIS NameClass entirely disallows non-ASCII spaces. The
			non-ASCII space characters are U+00A0 NO-BREAK SPACE, U+1680 OGHAM
			SPACE MARK, U+180E MONGOLIAN VOWEL SEPARATOR, U+2000 EN QUAD
			through U+200A HAIR SPACE, U+202F NARROW NO-BREAK SPACE, U+205F
			MEDIUM MATHEMATICAL SPACE, and U+3000 IDEOGRAPHIC SPACE. For
			migration purposes, deployments might want to convert non-ASCII
			space characters to ASCII space in simple user names.
			o SASLprep mapped the "characters commonly mapped to nothing" from
			Appendix B.1 of [RFC3454]) to nothing, whereas the PRECIS
			NameClass entirely disallows most of these characters, which
			correspond to the code points from the "M" category defined under
			Section 6.13 of [FRAMEWORK] (with the exception of U+1806
			MONGOLIAN TODO SOFT HYPHEN, which was "commonly mapped to nothing"
			in Unicode 3.2 but at the time of this writing does not have a
			derived property of Default_Ignorable_Code_Point in Unicode 6.1).
			For migration purposes, deployments might want to remove code
			points contained in the PRECIS "M" category from simple user
			names.
			o SASLprep allowed uppercase and titlecase characters, whereas this
			usage of the PRECIS NameClass maps uppercase and titlecase
			characters to their lowercase equivalents. For migration
			purposes, deployments can either convert uppercase and titlecase
			characters to their lowercase equivalents in simple user names
			(thus losing the case information) or preserve uppercase and
			titlecase characters and ignore the case difference when comparing
			simple user names.
			4.2. Passwords
			Depending on local service policy, migration from RFC 4013 to this
			specification might not involve any scrubbing of data (since
			passwords might not be stored in the clear anyway); however, service
			providers need to be aware of possible issues that might arise during
			migration. In particular:
	o SASLprep specified the use of Unicode Normalization Form KC		o SASLprep specified the use of Unicode Normalization Form KC
	(NFKC), whereas this usage of the PRECIS FreeClass employs Unicode		(NFKC), whereas this usage of the PRECIS FreeClass employs Unicode
	Normalization Form C (NFC). Because NFKC is more aggressive about		Normalization Form C (NFC). Because NFKC is more aggressive about
	finding matches than NFC, in practice this change is unlikely to		finding matches than NFC, in practice this change is unlikely to
	cause significant problems and indeed will probably result in		cause significant problems and indeed has the security benefit of
	fewer false positives when comparing passwords.		probably resulting in fewer false positives when comparing
			passwords. A few examples might suffice to indicate the nature of
			the problem: (1) U+017F LATIN SMALL LETTER LONG S is compatibility
			equivalent to U+0073 LATIN SMALL LETTER S (2) U+2163 ROMAN NUMERAL
			FOUR is compatibility equivalent to U+0049 LATIN CAPITAL LETTER I
			and U+0056 LATIN CAPITAL LETTER V (3) U+FB01 LATIN SMALL LIGATURE
			FI is compatibility equivalent to U+0066 LATIN SMALL LETTER F and
			U+0069 LATIN SMALL LETTER I. Under SASLprep, the use of NFKC also
			handled the mapping of fullwidth and halfwidth code points to
			their decomposition equivalents (see
			[I-D.yoneya-precis-mappings]). Although it is expected that code
			points with compatibility equivalents are rare in existing
			passwords, some passwords that matched when SASLprep was used
			might no longer work when the rules in this specification are
			applied.
	o SASLprep mapped the "characters commonly mapped to nothing" from		o SASLprep mapped the "characters commonly mapped to nothing" from
	Appendix B.1 of [RFC3454]) to nothing, whereas the PRECIS		Appendix B.1 of [RFC3454]) to nothing, whereas the PRECIS
	FreeClass entirely disallows such characters, which correspond to		FreeClass entirely disallows such characters, which correspond to
	the code points from the "M" category defined under Section 6.13		the code points from the "M" category defined under Section 6.13
	of [FRAMEWORK] (with the exception of U+1806 MONGOLIAN TODO SOFT		of [FRAMEWORK] (with the exception of U+1806 MONGOLIAN TODO SOFT
	HYPHEN, which was commonly mapped to nothing in Unicode 3.2 but at		HYPHEN, which was commonly mapped to nothing in Unicode 3.2 but at
	the time of this writing is allowed by Unicode 6.1).		the time of this writing is allowed by Unicode 6.1). In practice,
			this change will probably have no effect on comparison, but user-
	Note well that all code points and blocks not explicitly allowed in		oriented software might reject such code points instead of
	the PRECIS FreeClass are disallowed; this includes private use		ignoring them during password preparation.
	characters, surrogate code points, and the other code points and
	blocks defined as "Prohibited Output" in Section 2.3 of RFC 4013.
	4. Open Issues
	We need to compare the output obtained when applying the new rules
	with Unicode 3.2 and Unicode 6.1 data to the output obtained when
	applying the SASLprep rules with Unicode 3.2 data, then make sure
	that the PRECIS Working Group and KITTEN Working Group are
	comfortable with any changes to the Unicode characters that are
	allowed and disallowed. (See also the migration issues described in
	the foregoing sections.)
	5. Security Considerations		5. Security Considerations
	5.1. Password/Passphrase Strength		5.1. Password/Passphrase Strength
	The ability to include a wide range of characters in passwords and		The ability to include a wide range of characters in passwords and
	passphrases can increase the potential for creating a strong password		passphrases can increase the potential for creating a strong password
	with high entropy. However, in practice, the ability to include such		with high entropy. However, in practice, the ability to include such
	characters ought to be weighed against the possible need to reproduce		characters ought to be weighed against the possible need to reproduce
	them on various devices using various input methods.		them on various devices using various input methods.
	5.2. Reuse of PRECIS		5.2. Reuse of PRECIS
	The security considerations described in [FRAMEWORK] apply to the		The security considerations described in [FRAMEWORK] apply to the
	"NameClass" and "FreeClass" base string classes used in this document		"NameClass" and "FreeClass" base string classes used in this document
	for user names and passwords, respectively.		for simple user names and passwords, respectively.
	5.3. Reuse of Unicode		5.3. Reuse of Unicode
	The security considerations described in [UTR39] apply to the use of		The security considerations described in [UTR39] apply to the use of
	Unicode characters in user names and passwords.		Unicode characters in user names and passwords.
	6. IANA Considerations		6. IANA Considerations
	6.1. Use of NameClass		6.1. Use of NameClass
	The IANA shall add an entry to the PRECIS Usage Registry for reuse of		The IANA shall add an entry to the PRECIS Usage Registry for reuse of
	the PRECIS NameClass in SASL, as follows:		the PRECIS NameClass in SASL, as follows:
	Application Protocol: SASL/Kerberos.		Applicability: Usernames in SASL and Kerberos.
	Base Class: NameClass.		Base Class: NameClass.
	Subclassing: No.		Subclass: No.
	Directionality: The "Bidi Rule" defined in RFC 5893 applies.		Replaces: The SASLprep profile of Stringprep.
	Casemapping: Map uppercase and titlecase code points to their
	lowercase equivalents.
	Normalization: NFC.		Normalization: NFC.
	Specification: RFC XXXX.		Casemapping: Map uppercase and titlecase characters to lowercase.
			Additional Mappings: None.
			Directionality: The "Bidi Rule" defined in RFC 5893 applies.
			Specification: RFC XXXX. [Note to RFC Editor: please change XXXX to
			the number issued for this specification.]
	6.2. Use of FreeClass		6.2. Use of FreeClass
	The IANA shall add an entry to the PRECIS Usage Registry for reuse of		The IANA shall add an entry to the PRECIS Usage Registry for reuse of
	the PRECIS FreeClass in SASL, as follows:		the PRECIS FreeClass in SASL, as follows:
	Application Protocol: SASL/Kerberos.		Applicability: Passwords in SASL and Kerberos.
	Base Class: FreeClass		Base Class: FreeClass
	Subclassing: No.		Subclass: No.
	Directionality: The "Bidi Rule" defined in RFC 5893 applies.		Replaces: The SASLprep profile of Stringprep.
	Casemapping: None.
	Normalization: NFC.		Normalization: NFC.
	Specification: RFC XXXX.		Casemapping: None.
			Additional Mappings: Map non-ASCII space characters to ASCII space.
			Directionality: None.
			Specification: RFC XXXX. [Note to RFC Editor: please change XXXX to
			the number issued for this specification.]
	7. References		7. Open Issues
	7.1. Normative References		We need to compare the output obtained when applying the new rules
			with Unicode 3.2 and Unicode 6.1 data to the output obtained when
			applying the SASLprep rules with Unicode 3.2 data, then make sure
			that the PRECIS Working Group and KITTEN Working Group are
			comfortable with any changes to the Unicode characters that are
			allowed and disallowed. (See also the migration issues described
			under Section 4.)
			8. References
			8.1. Normative References
	[FRAMEWORK]		[FRAMEWORK]
	Saint-Andre, P. and M. Blanchet, "Precis Framework:		Saint-Andre, P. and M. Blanchet, "Precis Framework:
	Handling Internationalized Strings in Protocols",		Handling Internationalized Strings in Protocols",
	draft-ietf-precis-framework-05 (work in progress),		draft-ietf-precis-framework-05 (work in progress),
	August 2012.		August 2012.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119, March 1997.
	[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO		[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
	10646", STD 63, RFC 3629, November 2003.		10646", STD 63, RFC 3629, November 2003.
	[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax		[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
	Specifications: ABNF", STD 68, RFC 5234, January 2008.		Specifications: ABNF", STD 68, RFC 5234, January 2008.
	[UNICODE] The Unicode Consortium, "The Unicode Standard, Version		[UNICODE] The Unicode Consortium, "The Unicode Standard, Version
	6.1", 2012,		6.1", 2012,
	<http://www.unicode.org/versions/Unicode6.1.0/>.		<http://www.unicode.org/versions/Unicode6.1.0/>.
	7.2. Informative References		8.2. Informative References
	[MAPPINGS]		[I-D.yoneya-precis-mappings]
	YONEYA, Y. and T. NEMOTO, "Mapping characters for PRECIS		YONEYA, Y. and T. NEMOTO, "Mapping characters for PRECIS
	classes", draft-yoneya-precis-mappings-02 (work in		classes", draft-yoneya-precis-mappings-02 (work in
	progress), July 2012.		progress), July 2012.
	[RFC3454] Hoffman, P. and M. Blanchet, "Preparation of		[RFC3454] Hoffman, P. and M. Blanchet, "Preparation of
	Internationalized Strings ("stringprep")", RFC 3454,		Internationalized Strings ("stringprep")", RFC 3454,
	December 2002.		December 2002.
	[RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User Names		[RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User Names
	and Passwords", RFC 4013, February 2005.		and Passwords", RFC 4013, February 2005.
	skipping to change at page 10, line 48 ¶		skipping to change at page 11, line 34 ¶
	[RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in		[RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in
	Internationalization in the IETF", BCP 166, RFC 6365,		Internationalization in the IETF", BCP 166, RFC 6365,
	September 2011.		September 2011.
	[UTR39] The Unicode Consortium, "Unicode Technical Report #39:		[UTR39] The Unicode Consortium, "Unicode Technical Report #39:
	Unicode Security Mechanisms", August 2010,		Unicode Security Mechanisms", August 2010,
	<http://unicode.org/reports/tr39/>.		<http://unicode.org/reports/tr39/>.
	Appendix A. Differences from RFC 4013		Appendix A. Differences from RFC 4013
	The following substantive modifications were made from RFC 3920.		The following substantive modifications were made from RFC 4013.
	o A single SASLprep algorithm was replaced by two separate		o A single SASLprep algorithm was replaced by two separate
	algorithms: one for user names and another for passwords.		algorithms: one for simple user names and another for passwords.
	o The new preparation algorithms use PRECIS instead of a stringprep		o The new preparation algorithms use PRECIS instead of a stringprep
	profile. The new algorithms work independenctly of Unicode		profile. The new algorithms work independenctly of Unicode
	versions.		versions.
	o As recommended in the PRECIS framwork, changed the Unicode		o As recommended in the PRECIS framwork, changed the Unicode
	normalization form from NFKC to NFC.		normalization form from NFKC to NFC.
	o Some Unicode code points that were mapped to nothing in RFC 4013		o Some Unicode code points that were mapped to nothing in RFC 4013
	are simply disallowed by PRECIS.		are simply disallowed by PRECIS.
	Appendix B. Acknowledgements		Appendix B. Acknowledgements
	Thanks to Yoshiro YONEYA and Takahiro NEMOTO for implementation		Thanks to Yoshiro YONEYA and Takahiro NEMOTO for implementation
	feedback. Thanks also to Marc Blanchet, Joe Hildebrand, Alan DeKok,		feedback. Thanks also to Marc Blanchet, Joe Hildebrand, Alan DeKok,
	Simon Josefsson, Jonathan Lennox, Pete Resnick, and Andrew Sullivan		Simon Josefsson, Jonathan Lennox, Matt Miller, Pete Resnick, and
	for their input regarding the text.		Andrew Sullivan for their input regarding the text.
	This document borrows some text from RFC 4013 and RFC 6120.		This document borrows some text from RFC 4013 and RFC 6120.
	Authors' Addresses		Authors' Addresses
	Peter Saint-Andre		Peter Saint-Andre
	Cisco Systems, Inc.		Cisco Systems, Inc.
	1899 Wynkoop Street, Suite 600		1899 Wynkoop Street, Suite 600
	Denver, CO 80202		Denver, CO 80202
	USA		USA
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