PRECIS P. Saint-Andre
Internet-Draft Cisco Systems, Inc.
Obsoletes: 3454 (if approved) M. Blanchet
Intended status: Standards Track Viagenie
Expires: March 27, 2013 September 23, 2012
PRECIS Framework: Preparation and Comparison of Internationalized
Strings in Application Protocols
draft-ietf-precis-framework-06
Abstract
Application protocols using Unicode code points in protocol strings
need to prepare such strings in order to perform comparison
operations (e.g., for purposes of authentication or authorization).
This document defines a framework enabling application protocols to
perform the preparation and comparison of internationalized strings
(a.k.a. "PRECIS") in a way that depends on the properties of Unicode
code points and thus is 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). A specification that
reuses this framework can either directly use the base string classes
or subclass the base string classes as needed. This framework takes
an approach similar to the revised internationalized domain names in
applications (IDNA) technology (RFC 5890, RFC 5891, RFC 5892, RFC
5893, RFC 5894) and thus adheres to the high-level design goals
described in RFC 4690, albeit for application technologies other than
the Domain Name System (DNS). This document obsoletes RFC 3454.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 27, 2013.
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Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. String Classes . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. NameClass . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2.1. Valid . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2.2. Disallowed . . . . . . . . . . . . . . . . . . . . . . 8
3.2.3. Unassigned . . . . . . . . . . . . . . . . . . . . . . 8
3.2.4. Normalization . . . . . . . . . . . . . . . . . . . . 8
3.2.5. Casemapping . . . . . . . . . . . . . . . . . . . . . 8
3.2.6. Additional Mappings . . . . . . . . . . . . . . . . . 8
3.2.7. Directionality . . . . . . . . . . . . . . . . . . . . 8
3.3. FreeClass . . . . . . . . . . . . . . . . . . . . . . . . 9
3.3.1. Valid . . . . . . . . . . . . . . . . . . . . . . . . 9
3.3.2. Disallowed . . . . . . . . . . . . . . . . . . . . . . 9
3.3.3. Unassigned . . . . . . . . . . . . . . . . . . . . . . 9
3.3.4. Normalization . . . . . . . . . . . . . . . . . . . . 9
3.3.5. Casemapping . . . . . . . . . . . . . . . . . . . . . 10
3.3.6. Additional Mappings . . . . . . . . . . . . . . . . . 10
3.3.7. Directionality . . . . . . . . . . . . . . . . . . . . 10
4. Use of PRECIS String Classes . . . . . . . . . . . . . . . . . 10
4.1. Principles . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2. Subclassing . . . . . . . . . . . . . . . . . . . . . . . 11
4.3. A Note about Spaces . . . . . . . . . . . . . . . . . . . 11
5. Code Point Properties . . . . . . . . . . . . . . . . . . . . 12
6. Category Definitions Used to Calculate Derived Property
Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.1. LetterDigits (A) . . . . . . . . . . . . . . . . . . . . . 14
6.2. Unstable (B) . . . . . . . . . . . . . . . . . . . . . . . 15
6.3. IgnorableProperties (C) . . . . . . . . . . . . . . . . . 15
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6.4. IgnorableBlocks (D) . . . . . . . . . . . . . . . . . . . 15
6.5. LDH (E) . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.6. Exceptions (F) . . . . . . . . . . . . . . . . . . . . . . 15
6.7. BackwardCompatible (G) . . . . . . . . . . . . . . . . . . 17
6.8. JoinControl (H) . . . . . . . . . . . . . . . . . . . . . 17
6.9. OldHangulJamo (I) . . . . . . . . . . . . . . . . . . . . 17
6.10. Unassigned (J) . . . . . . . . . . . . . . . . . . . . . . 18
6.11. ASCII7 (K) . . . . . . . . . . . . . . . . . . . . . . . . 18
6.12. Controls (L) . . . . . . . . . . . . . . . . . . . . . . . 18
6.13. PrecisIgnorableProperties (M) . . . . . . . . . . . . . . 18
6.14. Spaces (N) . . . . . . . . . . . . . . . . . . . . . . . . 19
6.15. Symbols (O) . . . . . . . . . . . . . . . . . . . . . . . 19
6.16. Punctuation (P) . . . . . . . . . . . . . . . . . . . . . 19
6.17. HasCompat (Q) . . . . . . . . . . . . . . . . . . . . . . 19
6.18. OtherLetterDigits (R) . . . . . . . . . . . . . . . . . . 19
7. Calculation of the Derived Property . . . . . . . . . . . . . 20
8. Code Points . . . . . . . . . . . . . . . . . . . . . . . . . 21
9. Security Considerations . . . . . . . . . . . . . . . . . . . 21
9.1. General Issues . . . . . . . . . . . . . . . . . . . . . . 21
9.2. Use of the NameClass . . . . . . . . . . . . . . . . . . . 21
9.3. Use of the FreeClass . . . . . . . . . . . . . . . . . . . 21
9.4. Local Character Set Issues . . . . . . . . . . . . . . . . 22
9.5. Visually Similar Characters . . . . . . . . . . . . . . . 22
9.6. Security of Passwords . . . . . . . . . . . . . . . . . . 24
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
10.1. PRECIS Derived Property Value Registry . . . . . . . . . . 25
10.2. PRECIS Base Classes Registry . . . . . . . . . . . . . . . 25
10.3. PRECIS Subclasses Registry . . . . . . . . . . . . . . . . 26
10.4. PRECIS Usage Registry . . . . . . . . . . . . . . . . . . 27
11. Interoperability Considerations . . . . . . . . . . . . . . . 28
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
12.1. Normative References . . . . . . . . . . . . . . . . . . . 29
12.2. Informative References . . . . . . . . . . . . . . . . . . 29
Appendix A. Codepoint Table . . . . . . . . . . . . . . . . . . . 31
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 66
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 67
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1. Introduction
As described in [I-D.ietf-precis-problem-statement], many IETF
protocols have used the Stringprep framework [RFC3454] as the basis
for preparing and comparing protocol strings that contain Unicode
code points [UNICODE]. The Stringprep framework was developed during
work on the original technology for internationalized domain names
(IDNs), here called "IDNA2003" [RFC3490], and Nameprep [RFC3491] was
the Stringprep profile for IDNs. At the time, Stringprep was
designed as a general framework so that other application protocols
could define their own Stringprep profiles for the preparation and
comparison of strings and identifiers, and a number of application
protocols did define such profiles.
After the publication of [RFC3454] in 2002, several significant
issues arose with the use of Stringprep in the IDN case, as
documented in [RFC4690] (most significantly, Stringprep was tied to
Unicode version 3.2). Therefore, the new IDNA specifications, here
called "IDNA2008" ([RFC5890], [RFC5891], [RFC5892], [RFC5893],
[RFC5894]), no longer use Stringprep and Nameprep. This migration
away from Stringprep for IDNs has prompted other "customers" of
Stringprep to consider new approaches to the preparation and
comparison of internationalized strings (a.k.a. "PRECIS"), as
described in [I-D.ietf-precis-problem-statement].
This document defines a framework for a post-Stringprep approach to
the preparation and comparison of internationalized strings in
application protocols, based on several principles:
1. Define a small set of base string classes appropriate for common
application protocol constructs such as usernames and free-form
strings.
2. Define each base string class in terms of Unicode code points and
their properties so that an algorithm can be used to determine
whether each code point or character category is valid,
disallowed, or unassigned.
3. Define string classes in terms of allowable code points, so that
any code points not explicitly allowed are forbidden.
4. Enable application protocols to subclass the base string classes
if needed, mainly to disallow particular code points that are
currently disallowed in the relevant application protocol (e.g.,
characters with special or reserved meaning, such as "@" and "/"
when used as separators within identifiers).
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5. Leave various mapping operations (e.g., case preservation or
lowercasing, Unicode normalization, mapping of certain characters
to nothing, handling of right-to-left characters) as the
responsibility of application protocols, as was done for IDNA2008
through an IDNA-specific mapping document [RFC5895].
It is expected that this framework will yield the following benefits:
o Application protocols will be more version-agile with regard to
the Unicode database.
o Implementers will be able to share code point tables and software
code across application protocols, most likely by means of
software libraries.
o End users will be able to acquire more accurate expectations about
the code points that are acceptable in various contexts. Given
this more uniform set of string classes, it is also expected that
copy/paste operations between software implementing different
application protocols will be more predictable and coherent.
Although this framework is similar to IDNA2008 and borrows some of
the character categories defined in [RFC5892], it defines additional
string classes and character categories to meet the needs of common
application protocols.
2. Terminology
Many important terms used in this document are defined in [RFC5890],
[RFC6365], [I-D.ietf-precis-problem-statement], and [UNICODE].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
3. String Classes
3.1. Overview
IDNA2008 essentially defines a base string class of internationalized
domain name, although it does not use the term "string class". (This
document does not define a string class for domain names, and
application protocols are strongly encouraged to use IDNA2008 as the
appropriate method to prepare domain names and hostnames.) Because
the IDN string class is designed to meet the particular requirements
of the Domain Name System (DNS), additional string classes are needed
for non-DNS applications.
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Starting in 2010, various "customers" of Stringprep began to discuss
the need to define a post-Stringprep approach to the preparation and
comparison of internationalized strings. As a result of analyzing
existing Stringprep profiles, this community concluded that most
existing uses could be addressed by two base string classes:
NameClass: a sequence of letters, numbers, and symbols that is used
to identify or address a network entity such as a user account, a
venue (e.g., a chatroom), an information source (e.g., a data
feed), or a collection of data (e.g., a file); the intent is that
this class will be very safe for use in a wide variety of
application protocols, with the result that safety has been
prioritized over inclusiveness for this class.
FreeClass: a sequence of letters, numbers, symbols, spaces, and
other code points that is used for free-form strings, including
passwords as well as display elements such as human-friendly
nicknames in chatrooms; the intent is that this class will allow
nearly any Unicode character, with the result that inclusiveness
has been prioritized over safety for this class (e.g., protocol
designers, application developers, service providers, and end
users might not understand or be able to enter all of the
characters that can be included in the FreeClass).
Although members of the community discussed the possibility of
defining other bases string classes (e.g., a class falling somewhere
between the NameClass and the FreeClass), they concluded that the
NameClass would be a safe choice meeting the needs of many or even
most application protocols, and that protocols needing a wider range
of Unicode characters could use the FreeClass directly or subclass it
if needed.
The following subsections discuss the NameClass and FreeClass in more
detail, with reference to the dimensions described in Section 3 of
[I-D.ietf-precis-problem-statement]. (Naturally, future documents
can define base string classes beyond the NameClass and FreeClass;
see Section 10.2.) Each string class (or a particular usage thereof)
is defined by the following behavioral rules:
Valid: defines which code points and character categories are
treated as valid input to the string.
Disallowed: defines which code points and character categories are
treated as disallowed for the string.
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Unassigned: defines application behavior in the presence of code
points that are unassigned, i.e. unknown for the version of
Unicode the application is built upon.
Normalization: defines which Unicode normalization form (D, KD, C,
or KC) is to be applied (see [UAX15]).
Casemapping: specifies if casemapping is performed (instead of case
preservation), and how the mapping is done (e.g., mapping
uppercase and titlecase characters to their lowercase
equivalents).
Directionality: defines application behavior in the presence of code
points that have directionality, in particular right-to-left code
points as defined in the Unicode database (see [UAX9]).
This document defines the valid, disallowed, and unassigned rules for
the NameClass and FreeClass. Application protocols that use these
string classes are responsible for defining the normalization,
casemapping, and directionality rules, as well as any additional
mappings to be applied (e.g., mapping fullwidth and halfwidth
characters to their decomposition equivalents).
NOTE: In order to ensure proper comparison, any normalization MUST be
completed before the application of additional mappings or the
process of checking whether a code point is valid, disallowed, or
unassigned.
3.2. NameClass
Most application technologies need strings that can be used to refer
to, include, or communicate things like usernames, file names, data
feed names, and chatroom names. We group such things into a class
called "NameClass" having the following features.
3.2.1. Valid
o Code points traditionally used as letters and numbers in writing
systems, i.e., the LetterDigits ("A") category first defined in
[RFC5892] and listed here under Section 6.1.
o Code points in the range U+0021 through U+007E, i.e., the ASCII7
("K") rule defined under Section 6.11. These code points are
"grandfathered" into PRECIS and thus are valid even if they would
otherwise be disallowed according to the property-based rules
specified in the next section.
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3.2.2. Disallowed
o Control characters, i.e., the Controls ("L") category defined
under Section 6.12.
o Ignorable characters, i.e., the PrecisIgnorableProperties ("M")
category defined under Section 6.13.
o Space characters, i.e., the Spaces ("N") category defined under
Section 6.14.
o Symbol characters, i.e., the Symbols ("O") category defined under
Section 6.15.
o Punctuation characters, i.e., the Punctuation ("P") category
defined under Section 6.16.
o Any character that has a compatibility equivalent, i.e., the
HasCompat ("Q") category defined under Section 6.17. These code
points are disallowed even if they would otherwise be valid
according to the property-based rules specified in the previous
section.
o Letters and digits other than the "traditional" letters and digits
allowed in IDNs, i.e., the OtherLetterDigits ("R") category
defined under Section 6.18.
3.2.3. Unassigned
Any code points that are not yet assigned in the Unicode character
set SHALL be considered Unassigned for purposes of the NameClass.
3.2.4. Normalization
The Unicode normalization form MUST be specified by each application
protocol that uses or subclasses the NameClass.
However, in accordance with [RFC5198], normalization form C (NFC) is
RECOMMENDED.
3.2.5. Casemapping
The casemapping rule MUST be specified by each application protocol
that uses or subclasses the NameClass.
3.2.6. Additional Mappings
Additional mapping rules (if any) MUST be specified by each
application protocol that uses or subclasses the NameClass.
3.2.7. Directionality
The directionality rule MUST be specified by each application
protocol that uses or subclasses the NameClass.
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3.3. FreeClass
Some application technologies need strings that can be used in a
free-form way, e.g., as a password in an authentication exchange (see
[I-D.melnikov-precis-saslprepbis] or a nickname in a chatroom (see
[I-D.ietf-precis-nickname]). We group such things into a class
called "FreeClass" having the following features.
NOTE: Consult Section 9.6 for relevant security considerations when
strings conforming to the FreeClass, or a subclass thereof, are used
as passwords.
3.3.1. Valid
o Traditional letters and numbers, i.e., the LetterDigits ("A")
category first defined in [RFC5892] and listed here under
Section 6.1.
o Letters and digits other than the "traditional" letters and digits
allowed in IDNs, i.e., the OtherLetterDigits ("R") category
defined under Section 6.18.
o Code points in the range U+0021 through U+007E, i.e., the ASCII7
("K") rule defined under Section 6.11.
o Any character that has a compatibility equivalent, i.e., the
HasCompat ("Q") category defined under Section 6.17.
o Space characters, i.e., the Spaces ("N") category defined under
Section 6.14.
o Symbol characters, i.e., the Symbols ("O") category defined under
Section 6.15.
o Punctuation characters, i.e., the Punctuation ("P") category
defined under Section 6.16.
3.3.2. Disallowed
o Control characters, i.e., the Controls ("L") category defined
under Section 6.12.
o Ignorable characters, i.e., the PrecisIgnorableProperties ("M")
category defined under Section 6.13.
3.3.3. Unassigned
Any code points that are not yet assigned in the Unicode character
set SHALL be considered Unassigned for purposes of the FreeClass.
3.3.4. Normalization
The Unicode normalization form MUST be specified by each application
protocol that uses or subclasses the FreeClass.
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However, in accordance with [RFC5198], normalization form C (NFC) is
RECOMMENDED.
3.3.5. Casemapping
The casemapping rule MUST be specified by each application protocol
that uses or subclasses the FreeClass.
In general, the combination of case preservation and case-insensitive
comparison of internationalized strings is NOT RECOMMENDED; instead,
application protocols SHOULD either (a) not preserve case but perform
case-insensitive comparison or (b) preserve case but perform case-
sensitive comparison.
In order to maximize entropy and minimize the potential for false
positives, it is NOT RECOMMENDED for application protocols to map
uppercase and titlecase code points to their lowercase equivalents
when strings conforming to the FreeClass, or a subclass thereof, are
used in passwords; instead, it is RECOMMENDED to preserve the case of
all code points contained in such strings and then perform case-
sensitive comparison. See also the related discussion in
[I-D.melnikov-precis-saslprepbis].
3.3.6. Additional Mappings
Additional mapping rules (if any) MUST be specified by each
application protocol that uses or subclasses the FreeClass.
3.3.7. Directionality
The directionality rule MUST be specified by each application
protocol that uses or subclasses the FreeClass.
4. Use of PRECIS String Classes
4.1. Principles
This document defines the valid, disallowed, and unassigned rules.
Application protocols that use the PRECIS string classes MUST define
the normalization, casemapping, and directionality rules. Such
definitions MUST at a minimum specify the following:
Normalization: Which Unicode normalization form (D, KD, C, or KC) is
to be applied (see [UAX15] for background information); in
accordance with [RFC5198], NFC is RECOMMENDED.
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Casemapping: Whether uppercase and titlecase code points are to be
(a) preserved or (b) mapped to lowercase.
Additional Mappings: Whether additional mappings are to be applied,
such as mapping fullwidth and halfwidth characters to their
decomposition mappings, mapping non-ASCII space characters to
ASCII space, or mapping certain characters to nothing.
Directionality: Whether any instance of the class that contains a
right-to-left code point is to be considered a right-to-left
string, or whether some other rule is to be applied (e.g., the
"Bidi Rule" from [RFC5893]).
4.2. Subclassing
Application protocols are allowed to subclass the base string classes
specified in this document. As the word "subclass" implies, a
subclass MUST NOT add as valid any code points or character
categories that are disallowed by the base string class. However, a
subclass MAY do either of the following:
1. Exclude specific code points that are included in the base string
class.
2. Exclude characters matching certain Unicode properties (e.g.,
math symbols) that are included in the base string class.
As a result, code points that are defined as valid for the base
string class being subclassed will be defined as disallowed for the
subclass.
Application protocols that subclass the PRECIS string classes MUST
register with the IANA as described under Section 10.3.
It is RECOMMENDED for subclass names to be of the form
"SubclassBaseClass", where the "Subclass" string is a differentiator
and "BaseClass" is the name of the base class being subclassed; for
example, the subclass of the NameClass used for localparts in the
Extensible Messaging and Presence Protocol (XMPP) is named
"LocalpartNameClass" [I-D.ietf-xmpp-6122bis].
4.3. A Note about Spaces
The NameClass does not allow spaces of any kind (even ASCII space,
U+0020). This might be counter-intuitive, given that spaces are
included between family names and personal names when representing
the full names of people (and full names might be used as usernames).
The consensus of the PRECIS Working Group is that spaces are
problematic for many reasons, for example because in some locales
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some devices are known to generate a character other than ASCII space
(such as ZERO WIDTH JOINER, U+200D) when a user performs an action
like hit the space bar on a keyboard. Working Group participants
also raised concerns about the fact that spaces are not always
visible, and that many Unicode characters might be confusable with
ASCII space.
Although some existing protocols, such as the Simple Authentication
and Security Layer (SASL) [RFC4422], might be used in ways that allow
a username to include spaces, the sense of the Working Group was that
such protocols could define an application-layer construct that
consists of instances of the PRECIS NameClass separated from each
other by instances of the ASCII space character (U+0020). One
consequence of this approach might be to effectively discourage the
use of ASCII space (or, even more problematically, non-ASCII space
characters) in newer application protocols; given the challenges
involved in properly handling space characters in usernames,
identifiers, and other protocol strings, the Working Group considered
this to be a feature, not a bug.
5. Code Point Properties
In order to implement the string classes described above, this
document does the following:
1. Reviews and classifies the collections of code points in the
Unicode character set by examining various code point properties.
2. Defines an algorithm for determining a derived property value,
which can vary depending on the string class being used by the
relevant application protocol.
This document is not intended to specify precisely how derived
property values are to be applied in protocol strings. That
information is the responsibility of the protocol specification that
uses or subclasses a base string class from this document.
The value of the property is to be interpreted as follows.
PROTOCOL VALID Those code points that are allowed to be used in any
PRECIS string class (NameClass and FreeClass). Code points with
this property value are permitted for general use in any string
class. The abbreviated term PVALID is used to refer to this value
in the remainder of this document.
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SPECIFIC CLASS PROTOCOL VALID Those code points that are allowed to
be used in specific string classes. Code points with this
property value are permitted for use in specific string classes.
In the remainder of this document, the abbreviated term *_PVAL is
used, where * = (NAME | FREE), i.e., either FREE_PVAL or
NAME_PVAL.
CONTEXTUAL RULE REQUIRED Some characteristics of the character, such
as its being invisible in certain contexts or problematic in
others, require that it not be used in labels unless specific
other characters or properties are present. The abbreviated term
CONTEXT is used to refer to this value in the remainder of this
document. As in IDNA2008, there are two subdivisions of
CONTEXTUAL RULE REQUIRED, the first for Join_controls (called
CONTEXTJ) and the second for other characters (called CONTEXTO).
DISALLOWED Those code points that must not permitted in any PRECIS
string class.
SPECIFIC CLASS DISALLOWED Those code points that are not to be
included in a specific string class. Code points with this
property value are not permitted in one of the string classes but
might be permitted in others. In the remainder of this document,
the abbreviated term *_DIS is used, where * = (NAME | FREE), i.e.,
either FREE_DIS or NAME_DIS.
UNASSIGNED Those code points that are not designated (i.e. are
unassigned) in the Unicode Standard.
The mechanisms described here allow determination of the value of the
property for future versions of Unicode (including characters added
after Unicode 5.2 or 6.1 depending on the category, since some
categories in this document are reused from IDNA2008 and therefore
were defined at the time of Unicode 5.2). Changes in Unicode
properties that do not affect the outcome of this process do not
affect this framework. For example, a character can have its Unicode
General_Category value [UNICODE] change from So to Sm, or from Lo to
Ll, without affecting the algorithm results. Moreover, even if such
changes were to result, the BackwardCompatible list (Section 6.7) can
be adjusted to ensure the stability of the results.
Some code points need to be allowed in exceptional circumstances, but
ought to be excluded in all other cases; these rules are also
described in other documents. The most notable of these are the Join
Control characters, U+200D ZERO WIDTH JOINER and U+200C ZERO WIDTH
NON-JOINER. Both of them have the derived property value CONTEXTJ.
A character with the derived property value CONTEXTJ or CONTEXTO
(CONTEXTUAL RULE REQUIRED) is not to be used unless an appropriate
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rule has been established and the context of the character is
consistent with that rule. It is invalid to generate a string
containing these characters unless such a contextual rule is found
and satisfied. PRECIS does not define its own contextual rules, but
instead re-uses the contextual rules defined for IDNA2008; please see
Appendix A of [RFC5892] for more information.
6. Category Definitions Used to Calculate Derived Property Value
The derived property obtains its value based on a two-step procedure:
1. Characters are placed in one or more character categories either
(1) based on core properties defined by the Unicode Standard or
(2) by treating the code point as an exception and addressing the
code point based on its code point value. These categories are
not mutually exclusive.
2. Set operations are used with these categories to determine the
values for a property that is specific to a given string class.
These operations are specified under Section 7.
(NOTE: Unicode property names and property value names might have
short abbreviations, such as "gc" for the General_Category property
and "Ll" for the Lowercase_Letter property value of the gc property.)
In the following specification of character categories, the operation
that returns the value of a particular Unicode character property for
a code point is designated by using the formal name of that property
(from the Unicode PropertyAliases.txt [1]) followed by '(cp)' for
"code point". For example, the value of the General_Category
property for a code point is indicated by General_Category(cp).
The first ten categories (A-J) shown below were previously defined
for IDNA2008 and are copied directly from [RFC5892]. Some of these
categories are reused in PRECIS and some of them are not; however,
the lettering of categories is retained to prevent overlap and to
ease implementation of both IDNA2008 and PRECIS in a single software
application. The next seven categories (K-Q) are specific to PRECIS.
6.1. LetterDigits (A)
NOTE: This category is defined in [RFC5892] and copied here for use
in PRECIS.
A: General_Category(cp) is in {Ll, Lu, Lm, Lo, Mn, Mc, Nd}
These rules identify characters commonly used in mnemonics and often
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informally described as "language characters".
For more information, see section 4.5 of [UNICODE].
The categories used in this rule are:
o Ll - Lowercase_Letter
o Lu - Uppercase_Letter
o Lm - Modifier_Letter
o Lo - Other_Letter
o Mn - Nonspacing_Mark
o Mc - Spacing_Mark
o Nd - Decimal_Number
6.2. Unstable (B)
NOTE: This category is defined in [RFC5892] but not used in PRECIS.
6.3. IgnorableProperties (C)
NOTE: This category is defined in [RFC5892] but not used in PRECIS.
See the "PrecisIgnorableProperties (M)" category below for a more
inclusive category used in PRECIS identifiers.
6.4. IgnorableBlocks (D)
NOTE: This category is defined in [RFC5892] but not used in PRECIS.
6.5. LDH (E)
NOTE: This category is defined in [RFC5892] but not used in PRECIS.
See the "ASCII7 (K)" category below for a more inclusive category
used in PRECIS identifiers.
6.6. Exceptions (F)
NOTE: This category is defined in [RFC5892] and used in PRECIS to
ensure consistent treatment of the relevant code points.
F: cp is in {00B7, 00DF, 0375, 03C2, 05F3, 05F4, 0640, 0660,
0661, 0662, 0663, 0664, 0665, 0666, 0667, 0668,
0669, 06F0, 06F1, 06F2, 06F3, 06F4, 06F5, 06F6,
06F7, 06F8, 06F9, 06FD, 06FE, 07FA, 0F0B, 3007,
302E, 302F, 3031, 3032, 3033, 3034, 3035, 303B,
30FB}
This category explicitly lists code points for which the category
cannot be assigned using only the core property values that exist in
the Unicode standard. The values are according to the table below:
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PVALID -- Would otherwise have been DISALLOWED
00DF; PVALID # LATIN SMALL LETTER SHARP S
03C2; PVALID # GREEK SMALL LETTER FINAL SIGMA
06FD; PVALID # ARABIC SIGN SINDHI AMPERSAND
06FE; PVALID # ARABIC SIGN SINDHI POSTPOSITION MEN
0F0B; PVALID # TIBETAN MARK INTERSYLLABIC TSHEG
3007; PVALID # IDEOGRAPHIC NUMBER ZERO
CONTEXTO -- Would otherwise have been DISALLOWED
00B7; CONTEXTO # MIDDLE DOT
0375; CONTEXTO # GREEK LOWER NUMERAL SIGN (KERAIA)
05F3; CONTEXTO # HEBREW PUNCTUATION GERESH
05F4; CONTEXTO # HEBREW PUNCTUATION GERSHAYIM
30FB; CONTEXTO # KATAKANA MIDDLE DOT
CONTEXTO -- Would otherwise have been PVALID
0660; CONTEXTO # ARABIC-INDIC DIGIT ZERO
0661; CONTEXTO # ARABIC-INDIC DIGIT ONE
0662; CONTEXTO # ARABIC-INDIC DIGIT TWO
0663; CONTEXTO # ARABIC-INDIC DIGIT THREE
0664; CONTEXTO # ARABIC-INDIC DIGIT FOUR
0665; CONTEXTO # ARABIC-INDIC DIGIT FIVE
0666; CONTEXTO # ARABIC-INDIC DIGIT SIX
0667; CONTEXTO # ARABIC-INDIC DIGIT SEVEN
0668; CONTEXTO # ARABIC-INDIC DIGIT EIGHT
0669; CONTEXTO # ARABIC-INDIC DIGIT NINE
06F0; CONTEXTO # EXTENDED ARABIC-INDIC DIGIT ZERO
06F1; CONTEXTO # EXTENDED ARABIC-INDIC DIGIT ONE
06F2; CONTEXTO # EXTENDED ARABIC-INDIC DIGIT TWO
06F3; CONTEXTO # EXTENDED ARABIC-INDIC DIGIT THREE
06F4; CONTEXTO # EXTENDED ARABIC-INDIC DIGIT FOUR
06F5; CONTEXTO # EXTENDED ARABIC-INDIC DIGIT FIVE
06F6; CONTEXTO # EXTENDED ARABIC-INDIC DIGIT SIX
06F7; CONTEXTO # EXTENDED ARABIC-INDIC DIGIT SEVEN
06F8; CONTEXTO # EXTENDED ARABIC-INDIC DIGIT EIGHT
06F9; CONTEXTO # EXTENDED ARABIC-INDIC DIGIT NINE
DISALLOWED -- Would otherwise have been PVALID
0640; DISALLOWED # ARABIC TATWEEL
07FA; DISALLOWED # NKO LAJANYALAN
302E; DISALLOWED # HANGUL SINGLE DOT TONE MARK
302F; DISALLOWED # HANGUL DOUBLE DOT TONE MARK
3031; DISALLOWED # VERTICAL KANA REPEAT MARK
3032; DISALLOWED # VERTICAL KANA REPEAT WITH VOICED SOUND MARK
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3033; DISALLOWED # VERTICAL KANA REPEAT MARK UPPER HALF
3034; DISALLOWED # VERTICAL KANA REPEAT WITH VOICED SOUND MARK
UPPER HA
3035; DISALLOWED # VERTICAL KANA REPEAT MARK LOWER HALF
303B; DISALLOWED # VERTICAL IDEOGRAPHIC ITERATION MARK
6.7. BackwardCompatible (G)
NOTE: This category is defined in [RFC5892] and copied here for use
in PRECIS. Because of how the PRECIS string classes are defined,
only changes that would result in code points being added to or
removed from the LetterDigits ("A") category would result in
backward-incompatible modifications to code point assignments.
Therefore, management of this category is handled via the processes
specified in [RFC5892].
G: cp is in {}
This category includes the code points for which property values in
versions of Unicode after 5.2 have changed in such a way that the
derived property value would no longer be PVALID or DISALLOWED. If
changes are made to future versions of Unicode so that code points
might change property value from PVALID or DISALLOWED, then this
table can be updated and keep special exception values so that the
property values for code points stay stable.
6.8. JoinControl (H)
NOTE: This category is defined in [RFC5892] and copied here for use
in PRECIS.
H: Join_Control(cp) = True
This category consists of Join Control characters (i.e., they are not
in LetterDigits (Section 6.1) but are still required in strings under
some circumstances).
6.9. OldHangulJamo (I)
NOTE: This category is defined in [RFC5892] and copied here for use
in PRECIS.
I: Hangul_Syllable_Type(cp) is in {L, V, T}
This category consists of all conjoining Hangul Jamo (Leading Jamo,
Vowel Jamo, and Trailing Jamo).
Elimination of conjoining Hangul Jamos from the set of PVALID
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characters results in restricting the set of Korean PVALID characters
just to preformed, modern Hangul syllable characters. Old Hangul
syllables, which must be spelled with sequences of conjoining Hangul
Jamos, are not PVALID for string classes.
6.10. Unassigned (J)
NOTE: This category is defined in [RFC5892] and copied here for use
in PRECIS.
J: General_Category(cp) is in {Cn} and
Noncharacter_Code_Point(cp) = False
This category consists of code points in the Unicode character set
that are not (yet) assigned. It should be noted that Unicode
distinguishes between 'unassigned code points' and 'unassigned
characters'. The unassigned code points are all but (Cn -
Noncharacters), while the unassigned *characters* are all but (Cn +
Cs).
6.11. ASCII7 (K)
This PRECIS-specific category exempts most characters in the ASCII-7
range from other rules that might be applied during PRECIS
processing, on the assumption that these code points are in such wide
use that disallowing them would be counter-productive.
K: cp is in {0021..007E}
6.12. Controls (L)
L: Control(cp) = True
6.13. PrecisIgnorableProperties (M)
This PRECIS-specific category is used to group code points that are
not recommended for use in PRECIS string classes.
M: Default_Ignorable_Code_Point(cp) = True or
Noncharacter_Code_Point(cp) = True
The definition for Default_Ignorable_Code_Point can be found in the
DerivedCoreProperties.txt [2] file, and at the time of Unicode 6.1 is
as follows:
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Other_Default_Ignorable_Code_Point
+ Cf (Format characters)
+ Variation_Selector
- White_Space
- FFF9..FFFB (Annotation Characters)
- 0600..0604, 06DD, 070F, 110BD (exceptional Cf characters
that should be visible)
6.14. Spaces (N)
This PRECIS-specific category is used to group code points that are
space characters.
N: General_Category(cp) is in {Zs}
6.15. Symbols (O)
This PRECIS-specific category is used to group code points that are
symbols.
O: General_Category(cp) is in {Sm, Sc, Sk, So}
6.16. Punctuation (P)
This PRECIS-specific category is used to group code points that are
punctuation characters.
P: General_Category(cp) is in {Pc, Pd, Ps, Pe, Pi, Pf, Po}
6.17. HasCompat (Q)
This PRECIS-specific category is used to group code points that have
compatibility equivalents as explained in Chapter 2 and Chapter 3 of
[UNICODE].
Q: toNFKC(cp) != cp
The toNFKC() operation returns the code point in normalization form
KC. For more information, see Section 5 of [UAX15].
6.18. OtherLetterDigits (R)
This PRECIS-specific category is used to group code points that are
letters and digits other than the "traditional" letters and digits
grouped under the LetterDigits (A) class (see Section 6.1).
R: General_Category(cp) is in {Lt, Nl, No, Me}
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7. Calculation of the Derived Property
Possible values of the derived property are:
o PVALID
o NAME_PVAL
o FREE_PVAL
o CONTEXTJ
o CONTEXTO
o DISALLOWED
o NAME_DIS
o FREE_DIS
o UNASSIGNED
NOTE: The value of the derived property calculated can depend on the
string class; for example, if an identifier used in an application
protocol is defined as using or subclassing the PRECIS NameClass then
a space character such as U+0020 would be assigned to NAME_DIS,
whereas if an identifier is defined as using or subclassing the
PRECIS FreeClass then the character would be assigned to FREE_PVAL.
For the sake of brevity, the designation "FREE_PVAL" is used in the
code point tables, instead of the longer designation "NAME_DIS or
FREE_PVAL". In practice, the derived properties NAME_PVAL and
FREE_DIS are not used in this specification, since every NAME_PVAL
code point is PVALID and every FREE_DIS code point is DISALLOWED.
The algorithm to calculate the value of the derived property is as
follows. (NOTE: Use of the name of a rule (such as "Exception")
implies the set of code points that the rule defines, whereas the
same name as a function call (such as "Exception(cp)") implies the
value that the code point has in the Exceptions table.)
If .cp. .in. Exceptions Then Exceptions(cp);
Else If .cp. .in. BackwardCompatible Then BackwardCompatible(cp);
Else If .cp. .in. Unassigned Then UNASSIGNED;
Else If .cp. .in. ASCII7 Then PVALID;
Else If .cp. .in. JoinControl Then CONTEXTJ;
Else If .cp. .in. PrecisIgnorableProperties Then DISALLOWED;
Else If .cp. .in. Controls Then DISALLOWED;
Else If .cp. .in. OldHangulJamo Then DISALLOWED;
Else If .cp. .in. LetterDigits Then PVALID;
Else If .cp. .in. OtherLetterDigits Then NAME_DIS or FREE_PVAL;
Else If .cp. .in. Spaces Then NAME_DIS or FREE_PVAL;
Else If .cp. .in. Symbols Then NAME_DIS or FREE_PVAL;
Else If .cp. .in. Punctuation Then NAME_DIS or FREE_PVAL;
Else If .cp. .in. HasCompat Then NAME_DIS or FREE_PVAL;
Else DISALLOWED;
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8. Code Points
The Categories and Rules defined under Section 6 and Section 7 apply
to all Unicode code points. The table in Appendix A shows, for
illustrative purposes, the consequences of the categories and
classification rules, and the resulting property values.
The list of code points that can be found in Appendix A is non-
normative. Instead, the rules defined by Section 6 and Section 7 are
normative, and any tables are derived from the rules.
9. Security Considerations
9.1. General Issues
The security of applications that use this framework can depend in
part on the proper preparation and comparison of internationalized
strings. For example, such strings can be used to make
authentication and authorization decisions, and the security of an
application could be compromised if an entity providing a given
string is connected to the wrong account or online resource based on
different interpretations of the string.
Specifications of application protocols that use this framework are
encouraged to describe how internationalized strings are used in the
protocol, including the security implications of any false positives
and false negatives that might result from various comparison
operations. For some helpful guidelines, refer to
[I-D.iab-identifier-comparison], [RFC5890], [UTR36], and [UTR39].
9.2. Use of the NameClass
Strings that conform to the NameClass and any subclass thereof are
intended to be relatively safe for use in a broad range of
applications, primarily because they include only letters, digits,
and "grandfathered" non-space characters from the ASCII range; thus
they exclude spaces, characters with compatibility equivalents, and
almost all symbols and punctuation marks. However, because such
strings can still include so-called confusable characters (see
Section 9.5, protocol designers and implementers are encouraged to
pay close attention to the security considerations described
elsewhere in this document.
9.3. Use of the FreeClass
Strings that conform to the FreeClass and many subclasses thereof can
include virtually any Unicode character. This makes the FreeClass
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quite expressive, but also problematic from the perspective of
possible user confusion. Protocol designers are hereby warned that
the FreeClass contains codepoints they might not understand, and are
encouraged to use or subclass the NameClass wherever feasible;
however, if an application protocol requires more code points than
are allowed by the NameClass, protocol designers are encouraged to
define a subclass of the FreeClass that restricts the allowable code
points as tightly as possible. (The working group considered the
option of allowing superclasses as well as subclasses of PRECIS
string classes, but decided against allowing superclasses to reduce
the likelihood of security and interoperability problems.)
9.4. Local Character Set Issues
When systems use local character sets other than ASCII and Unicode,
these specifications leave the problem of converting between the
local character set and Unicode up to the application or local
system. If different applications (or different versions of one
application) implement different rules for conversions among coded
character sets, they could interpret the same name differently and
contact different application servers or other network entities.
This problem is not solved by security protocols, such as Transport
Layer Security (TLS) [RFC5246] and the Simple Authentication and
Security Layer (SASL) [RFC4422], that do not take local character
sets into account.
9.5. Visually Similar Characters
Some characters are visually similar and thus can cause confusion
among humans. Such characters are often called "confusable
characters" or "confusables".
The problem of confusable characters is not necessarily caused by the
use of Unicode code points outside the ASCII range. For example, in
some presentations and to some individuals the string "ju1iet"
(spelled with the Arabic numeral one as the third character) might
appear to be the same as "juliet" (spelled with the lowercase version
of the letter "L"), especially on casual visual inspection. This
phenomenon is sometimes called "typejacking".
However, the problem is made more serious by introducing the full
range of Unicode code points into protocol strings. For example, the
characters U+13DA U+13A2 U+13B5 U+13AC U+13A2 U+13AC U+13D2 from the
Cherokee block look similar to the ASCII characters "STPETER" as they
might look when presented using a "creative" font family.
In some examples of confusable characters, it is unlikely that the
average human could tell the difference between the real string and
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the fake string. (Indeed, there is no programmatic way to
distinguish with full certainty which is the fake string and which is
the real string; in some contexts, the string formed of Cherokee
characters might be the real string and the string formed of ASCII
characters might be the fake string.) Because PRECIS-compliant
strings can contain almost any properly-encoded Unicode code point,
it can be relatively easy to fake or mimic some strings in systems
that use the PRECIS framework. The fact that some strings are easily
confused introduces security vulnerabilities of the kind that have
also plagued the World Wide Web, specifically the phenomenon known as
phishing.
Despite the fact that some specific suggestions about identification
and handling of confusable characters appear in the Unicode Security
Considerations [UTR36], it is also true (as noted in [RFC5890]) that
"there are no comprehensive technical solutions to the problems of
confusable characters". Because it is impossible to map visually
similar characters without a great deal of context (such as knowing
the font families used), the PRECIS framework does nothing to map
similar-looking characters together, nor does it prohibit some
characters because they look like others.
Nevertheless, specifications for application protocols that use this
framework MUST describe how confusable characters can be used to
compromise the security of systems that use the protocol in question,
along with any protocol-specific suggestions for overcoming those
threats. In particular, software implementations and service
deployments that use PRECIS-based technologies are strongly
encouraged to define and implement consistent policies regarding the
registration, storage, and presentation of visually similar
characters. The following recommendations are appropriate:
1. An application service SHOULD define a policy that specifies the
scripts or blocks of characters that the service will allow to be
registered (e.g., in an account name) or stored (e.g., in a file
name). Such a policy SHOULD be informed by the languages and
scripts that are used to write registered account names; in
particular, to reduce confusion, the service SHOULD forbid
registration or storage of stings that contain characters from
more than one script and SHOULD restrict registrations to
characters drawn from a very small number of scripts (e.g.,
scripts that are well-understood by the administrators of the
service, to improve manageability).
2. User-oriented application software SHOULD define a policy that
specifies how internationalized strings will be presented to a
human user. Because every human user of such software has a
preferred language or a small set of preferred languages, the
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software SHOULD gather that information either explicitly from
the user or implicitly via the operating system of the user's
device. Furthermore, because most languages are typically
represented by a single script or a small set of scripts, and
because most scripts are typically contained in one or more
blocks of characters, the software SHOULD warn the user when
presenting a string that mixes characters from more than one
script or block, or that uses characters outside the normal range
of the user's preferred language(s). (Such a recommendation is
not intended to discourage communication across different
communities of language users; instead, it recognizes the
existence of such communities and encourages due caution when
presenting unfamiliar scripts or characters to human users.)
9.6. Security of Passwords
Two goals of passwords are to maximize the amount of entropy and to
minimize the potential for false positives. These goals can be
achieved in part by allowing a wide range of code points and by
ensuring that passwords are handled in such a way that code points
are not compared aggressively. Therefore, it is NOT RECOMMENDED for
application protocols to subclass the FreeClass for use in passwords
in a way that removes entire categories (e.g., by disallowing symbols
or punctuation). Furthermore, it is NOT RECOMMENDED for application
protocols to map uppercase and titlecase code points to their
lowercase equivalents in such strings; instead, it is RECOMMENDED to
preserve the case of all code points contained in such strings and to
compare them in a case-sensitive manner.
That said, software implementers need to be aware that there exist
tradeoffs between entropy and usability. For example, allowing a
user to establish a password containing "uncommon" code points might
make it difficult for the user to access a service when using an
unfamiliar or constrained input device.
Some application protocols use passwords directly, whereas others
reuse technologies that themselves process passwords (one example of
such a technology is the Simple Authentication and Security Layer
[RFC4422]). Moreover, passwords are often carried by a sequence of
protocols with backend authentication systems or data storage systems
such as RADIUS [RFC2865] and LDAP [RFC4510]. Developers of
application protocols are encouraged to look into reusing these
profiles instead of defining new ones, so that end-user expectations
about passwords are consistent no matter which application protocol
is used.
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10. IANA Considerations
10.1. PRECIS Derived Property Value Registry
IANA is requested to create a PRECIS-specific registry with the
Derived Properties for the versions of Unicode that are released
after (and including) version 6.1. The derived property value is to
be calculated in cooperation with a designated expert [RFC5226]
according to the rules specified under Section 6 and Section 7, not
by copying the non-normative table found under Appendix A.
The IESG is to be notified if backward-incompatible changes to the
table of derived properties are discovered or if other problems arise
during the process of creating the table of derived property values
or during expert review. Changes to the rules defined under
Section 6 and Section 7) require IETF Review, as described in
[RFC5226].
10.2. PRECIS Base Classes Registry
IANA is requested to create a registry of PRECIS base string classes.
In accordance with [RFC5226], the registration policy is "RFC
Required".
The registration template is as follows:
Base Class: [the name of the base class]
Description: [a brief description of the base class and its intended
use, e.g., "A sequence of letters, numbers, and symbols that is
used to identify or address a network entity."]
Normalization: [which Unicode normalization form is applied, e.g.,
"NFC"; or "Application Specific" if to be defined by protocols
that use the base class]
Casemapping: [the behavioral rule for handling of case, e.g., "Map
uppercase and titlecase characters to lowercase."; or "Application
Specific" if to be defined by protocols that use the base class]
Additional Mappings: [any additional mappings are required or
recommended, e.g., "Map non-ASCII space characters to ASCII
space."; or "Application Specific" if to be defined by protocols
that use the base class]
Directionality: [the behavioral rule for handling of right-to-left
code points, e.g., "The 'Bidi Rule' defined in RFC 5893 applies.";
or "Application Specific" if to be defined by protocols that use
the base class]
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Specification: [the RFC number]
The initial registrations are as follows:
Base Class: FreeClass.
Description: A sequence of letters, numbers, symbols, spaces, and
other code points that is used for free-form strings.
Normalization: Application Specific.
Casemapping: Application Specific.
Additional Mappings: Application Specific.
Directionality: Application Specific.
Specification: RFC XXXX. [Note to RFC Editor: please change XXXX to
the number issued for this specification.]
Base Class: NameClass.
Description: A sequence of letters, numbers, and symbols that is
used to identify or address a network entity.
Normalization: Application Specific.
Casemapping: Application Specific.
Additional Mappings: Application Specific.
Directionality: Application Specific.
Specification: RFC XXXX. [Note to RFC Editor: please change XXXX to
the number issued for this specification.]
10.3. PRECIS Subclasses Registry
IANA is requested to create a registry of subclasses that use the
PRECIS base string classes. In accordance with [RFC5226], the
registration policy is "Expert Review". This policy was chosen in
order to ensure that "customers" of PRECIS receive appropriate
guidance regarding the sometimes complex and subtle
internationalization issues related to subclassing of PRECIS base
classes.
The registration template is as follows:
Subclass: [the name of the subclass]
Base Class: [which base class is being subclassed]
Exclusions: [a brief description of the specific code points that
are excluded or of the properties based on which characters are
excluded, e.g., "Eight legacy characters in the ASCII range" or
"Any character that has a compatibility equivalent, i.e., the
HasCompat category"]
Specification: [a pointer to relevant documentation, such as an RFC
or Internet-Draft]
In order to request a review, the registrant shall send a completed
template to the precis@ietf.org list or its designated successor.
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Factors to focus on while reviewing subclass registrations include
the following:
o Is the problem well-defined?
o Is it clear what applications will use this subclass?
o Would an existing base class or subclass solve the problem?
o Are the defined exclusions a reasonable solution to the problem
for the relevant applications?
o Is the subclass clearly defined?
o Does the subclass reduce the degree to which human users could be
surprised by application behavior (the "principle of least user
surprise")?
o Is the subclass based on an appropriate dividing line between user
interface (culture, context, intent, locale, device limitations,
etc.) and the use of conformant strings in protocol elements?
o Does the subclass introduce any new security concerns (e.g., false
positives for authentication or authorization)?
10.4. PRECIS Usage Registry
IANA is requested to create a registry of application protocols that
use the base string classes. The registry will include one entry for
each use (e.g., if a protocol uses both the NameClass and the
FreeClass then the specification for that protocol would submit two
registrations). In accordance with [RFC5226], the registration
policy is "Expert Review". This policy was chosen in order to ensure
that "customers" of PRECIS receive appropriate guidance regarding the
sometimes complex and subtle internationalization issues related to
use of PRECIS base classes.
The registration template is as follows:
Applicability: [the specific protocol elements to which this usage
applies, e.g., "Localparts in XMPP addresses."]
Base Class: [the base string class that is being used or subclassed]
Subclass: [whether the protocol has defined a subclass of the base
class and, if so, the name of the subclass, e.g., "Yes,
LocalpartNameClass."]
Replaces: [the Stringprep profile that this PRECIS usage replaces,
if any]
Normalization: [which Unicode normalization form is applied, e.g.,
"NFC"]
Casemapping: [the behavioral rule for handling of case, e.g., "Map
uppercase and titlecase characters to lowercase."]
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Additional Mappings: [any additional mappings are required or
recommended, e.g., "Map non-ASCII space characters to ASCII
space."]
Directionality: [the behavioral rule for handling of right-to-left
code points, e.g., "The 'Bidi Rule' defined in RFC 5893 applies."]
Specification: [a pointer to relevant documentation, such as an RFC
or Internet-Draft]
In order to request a review, the registrant shall send a completed
template to the precis@ietf.org list or its designated successor.
Factors to focus on while reviewing usage registrations include the
following:
o Does the specification define what kinds of applications are
involved and the protocol elements to which this usage applies?
o Is there a base class or subclass that would be more appropriate
to use?
o Are the normalization, casemapping, additional mapping, and
directionality rules appropriate for the intended use?
o Does the usage reduce the degree to which human users could be
surprised by application behavior (the "principle of least user
surprise")?
o Is the usage based on an appropriate dividing line between user
interface (culture, context, intent, locale, device limitations,
etc.) and the use of conformant strings in protocol elements?
o Does the usage introduce any new security concerns (e.g., false
positives for authentication or authorization)?
11. Interoperability Considerations
Although strings that are consumed in PRECIS-based application
protocols are often encoded using UTF-8 [RFC3629], the exact encoding
is a matter for the application protocol that reuses PRECIS, not for
the PRECIS framework.
It is known that some existing systems are unable to support the full
Unicode character set, or even any characters outside the ASCII
range. If two (or more) applications need to interoperate when
exchanging data (e.g., for the purpose of authenticating a username
or password), they will naturally need have in common at least one
coded character set (as defined by [RFC6365]). Establishing such a
baseline is a matter for the application protocol that reuses PRECIS,
not for the PRECIS framework.
12. References
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12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for Network
Interchange", RFC 5198, March 2008.
[UNICODE] The Unicode Consortium, "The Unicode Standard, Version
6.1", 2012,
.
12.2. Informative References
[I-D.iab-identifier-comparison]
Thaler, D., "Issues in Identifier Comparison for Security
Purposes", draft-iab-identifier-comparison-04 (work in
progress), August 2012.
[I-D.ietf-precis-nickname]
Saint-Andre, P., "Preparation and Comparison of
Nicknames", draft-ietf-precis-nickname-01 (work in
progress), September 2012.
[I-D.ietf-precis-problem-statement]
Sullivan, A. and M. Blanchet, "Stringprep Revision Problem
Statement", draft-ietf-precis-problem-statement-08 (work
in progress), September 2012.
[I-D.ietf-xmpp-6122bis]
Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Address Format",
draft-ietf-xmpp-6122bis-03 (work in progress),
August 2012.
[I-D.melnikov-precis-saslprepbis]
Melnikov, A. and P. Saint-Andre, "Username and Password
Preparation Algorithms",
draft-melnikov-precis-saslprepbis-03 (work in progress),
September 2012.
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)",
RFC 2865, June 2000.
[RFC3454] Hoffman, P. and M. Blanchet, "Preparation of
Internationalized Strings ("stringprep")", RFC 3454,
December 2002.
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[RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
"Internationalizing Domain Names in Applications (IDNA)",
RFC 3490, March 2003.
[RFC3491] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
Profile for Internationalized Domain Names (IDN)",
RFC 3491, March 2003.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[RFC4422] Melnikov, A. and K. Zeilenga, "Simple Authentication and
Security Layer (SASL)", RFC 4422, June 2006.
[RFC4510] Zeilenga, K., "Lightweight Directory Access Protocol
(LDAP): Technical Specification Road Map", RFC 4510,
June 2006.
[RFC4690] Klensin, J., Faltstrom, P., Karp, C., and IAB, "Review and
Recommendations for Internationalized Domain Names
(IDNs)", RFC 4690, September 2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework",
RFC 5890, August 2010.
[RFC5891] Klensin, J., "Internationalized Domain Names in
Applications (IDNA): Protocol", RFC 5891, August 2010.
[RFC5892] Faltstrom, P., "The Unicode Code Points and
Internationalized Domain Names for Applications (IDNA)",
RFC 5892, August 2010.
[RFC5893] Alvestrand, H. and C. Karp, "Right-to-Left Scripts for
Internationalized Domain Names for Applications (IDNA)",
RFC 5893, August 2010.
[RFC5894] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Background, Explanation, and
Rationale", RFC 5894, August 2010.
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[RFC5895] Resnick, P. and P. Hoffman, "Mapping Characters for
Internationalized Domain Names in Applications (IDNA)
2008", RFC 5895, September 2010.
[RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in
Internationalization in the IETF", BCP 166, RFC 6365,
September 2011.
[UAX15] The Unicode Consortium, "Unicode Standard Annex #15:
Unicode Normalization Forms", September 2010,
.
[UAX9] The Unicode Consortium, "Unicode Standard Annex #9:
Unicode Bidirectional Algorithm", September 2010,
.
[UTR36] The Unicode Consortium, "Unicode Technical Report #36:
Unicode Security Considerations", August 2010,
.
[UTR39] The Unicode Consortium, "Unicode Technical Report #39:
Unicode Security Mechanisms", August 2010,
.
URIs
[1]
[2]
Appendix A. Codepoint Table
WARNING: The following table is incomplete and very likely contains
errors!
If one applies the property calculation rules from Section 7 to the
code points 0x0000 to 0x10FFFF in Unicode 6.1, the result is as shown
in the following table, in Unicode Character Database (UCD) format.
The columns of the table are as follows:
1. The code point or codepoint range.
2. The assignment for the code point or range, where the value is
one of PVALID, DISALLOWED, UNASSIGNED, CONTEXTO, CONTEXTJ, or
FREE_PVAL (which includes NAME_DIS).
3. The name or names for the code point or range.
This table is non-normative, and included only for illustrative
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purposes. Please note that the strings displayed in the third column
are not necessarily the formal name of the code point (as defined in
[UNICODE]) because the fixed width of the RFC format necessitated
truncation of many names.
0000..001F ; DISALLOWED #
0020 ; FREE_PVAL # SPACE
0021..007E ; PVALID # EXCLAM MARK .. TILDE
007F..009F ; DISALLOWED #
00A0..00A9 ; FREE_PVAL # NO-BREAK SPACE .. COPYRIGHT SIGN
00AA ; PVALID # FEMININE ORDINAL INDICATOR
00AB..00AC ; FREE_PVAL # NO-BREAK SPACE .. NOT SIGN
00AD ; DISALLOWED # SOFT HYPH
00AE..00B6 ; FREE_PVAL # REGISTERED SIGN .. PILCROW SIGN
00B7 ; CONTEXTO # MIDDLE DOT
00B8..00BF ; FREE_PVAL # CEDILLA..INV QUEST IND
00C0..00D6 ; PVALID # LAT CAP LET A W GRAV..LAT CAP O
00D7 ; FREE_PVAL # MULTIPLICATION SIGN
00D8..00F6 ; PVALID # LAT CAP LET O W STROKE..LAT SM
00F7 ; FREE_PVAL # DIVISION SIGN
00F8..0131 ; PVALID # LAT SM LET O W STROKE..LAT SM LET
0132..0133 ; FREE_PVAL # LAT CAP LIG IJ..LAT SM LIB IJ
0134..013E ; PVALID # LAT CAP LET J W CIRCUM..LAT SM LET
013F..0140 ; FREE_PVAL # LAT CAP LET L W MID DOT..LAT SM LET
0141..0148 ; PVALID # LAT CAP LET L W STROKE..LAT SM LET
0149 ; FREE_PVAL # LAT SM LET N PRECEDED BY APOS
014A..017E ; PVALID # LAT CAP LET ENG..LAT SM LET Z W CA
017F ; FREE_PVAL # LAT SM LET LONG S
0180..01C3 ; PVALID # LAT SM LET B W STROKE..LAT LET RETR
01C4..01CC ; FREE_PVAL # LAT CAP LET DZ W CARON..LAT SM
01CD..01F0 ; PVALID # LAT CAP LET A W CARON..LAT SM LET J
01F1..01F3 ; FREE_PVAL # LAT CAP LET DZ..LAT SM LET DZ
01F4..02AF ; PVALID # LAT CAP LET G W ACUTE..LAT SM
02B0..02B8 ; FREE_PVAL # MOD LET SM H..MOD LET SM Y
02B9..02C1 ; PVALID # MOD LET PRIME..MOD LET REV GLOT ST
02C2..02C5 ; FREE_PVAL # MOD LET L ARROW..MOD LET D ARROW
02C6..02D1 ; PVALID # MOD LET CIRCUM ACC..MOD LET HALF TR
02D2..02EB ; FREE_PVAL # MOD LET CENT R HALF RING..MOD LET Y
02EC ; PVALID # MOD LET VOICING
02ED ; FREE_PVAL # MOD LET UNASPIRATED
02EE ; PVALID # MOD LET DOUBLE APOS
02EF..02FF ; FREE_PVAL # MOD LET LOW D ARR..MOD LET LOW L AR
0300..0374 ; PVALID # COMB GRAVE ACCENT..GREEK NUM SIGN
0375 ; CONTEXTO # GREEK LOW NUM SIGN
0376..0377 ; PVALID # GR CAP LET PAMPHYLIAN DIGAMMA..GR S
0378..0379 ; UNASSIGNED # ..
037A..037D ; PVALID # GR YPOGEGRAMMENI..GR SM REV DOT LUN
037E ; FREE_PVAL # GREEK QUEST MARK
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037F..0383 ; UNASSIGNED # ..
0384..0385 ; FREE_PVAL # GREEK TONOS..GREEK DIALYTIKA TONOS
0386 ; PVALID # GR CAP LET ALPHA W TONOS
0387 ; FREE_PVAL # GREEK ANO TELEIA
0388..038A ; PVALID # GR CAP LET EPSILON W TONOS..GR CAP
038B ; UNASSIGNED #
038C ; PVALID # GREEK CAP LET OMICRON W TONOS
038D ; UNASSIGNED #
038E..03A1 ; PVALID # GR CAP LET EPSILON W TONOS..GR CAP
03A2 ; UNASSIGNED #
03A3..03CF ; PVALID # GREEK CAP LET SIGMA..GR CAP
03D0..03D2 ; FREE_PVAL # GR BETA SYM..GR UPSILON W HOOK
03D3..03D4 ; PVALID # GR UPSILON W ACUTE AND HOOK..GR UP
03D5..03D6 ; FREE_PVAL # GR PHI SYM..GR PI SYM
03D7..03EF ; PVALID # GR KAI SYM..COPT SM LET DEI
03F0..03F2 ; FREE_PVAL # GR KAPPA SYM..GR LUNATE SIGMA
03F3 ; PVALID # GREEK LET YOT
03F4..03F6 ; FREE_PVAL # GR CAP THETA..GR REV LUNATE EPSILON
03F7..03F8 ; PVALID # GR CAP LET SHO..GR SM LET SHO
03F9 ; FREE_PVAL # GREEK CAP LUNATE SIGMA SYM
03FA..0481 ; PVALID # GR CAP LET SAN..CYR SML LET KOPPA
0482 ; FREE_PVAL # CYR THOUSANDS SIGN
0483..0487 ; PVALID # COMB CYR TITLO..COMB CYR POK
0488..048A ; FREE_PVAL # COMB CYR HUNDRED THOUSANDS SIGN..C
048B..0527 ; PVALID # CYR SM LET SHORT I W TAIL..CYR S
0528..0530 ; UNASSIGNED # ..
0531..0556 ; PVALID # ARM CAP LET AYB..ARM CAP LET FEH
0557..0558 ; UNASSIGNED # ..
0559 ; PVALID # ARM MOD LET LEFT HALF RING
055A..055F ; FREE_PVAL # ARM APOS..ARM ABBREV
0560 ; UNASSIGNED #
0561..0586 ; PVALID # ARM SM LET AYB..ARMENIAN SM LE
0587 ; FREE_PVAL # ARM SM LIG ECH YIWN
0588 ; UNASSIGNED #
0589..058A ; FREE_PVAL # ARMENIAN FULL STOP..ARMENIAN HYPH
058B..058E ; UNASSIGNED # ..
058F ; FREE_PVAL # ARMENIAN DRAM SIGN
0590 ; UNASSIGNED #
0591..05BD ; PVALID # HEBR ACC ETNAHTA..HEBR PNT ME
05BE ; FREE_PVAL # HEBR PUNCT MAQAF
05BF ; PVALID # HEBR PNT RAFE
05C0 ; FREE_PVAL # HEBR PUNCT PASEQ
05C1..05C2 ; PVALID # HEBR PNT SHIN DOT..HEBR PNT SIN DOT
05C3 ; FREE_PVAL # HEBR PUNCT SOF PASUQ
05C4..05C5 ; PVALID # HEBR MARK UP DOT..HEBR MARK LOW DOT
05C6 ; FREE_PVAL # HEBR PUNCT NUN HAFUKHA
05C7 ; PVALID # HEBR PNT QAMATS QATAN
05C8..05CF ; UNASSIGNED # ..
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05D0..05EA ; PVALID # HEBR LET ALEF..HEBR LET TAV
05EB..05EF ; UNASSIGNED # ..
05F0..05F2 ; PVALID # HEBR LIG YIDDISH DOUBLE VAV..HEBR L
05F3..05F4 ; CONTEXTO # HEBR PUNCT GERESH..HEBR PUNCTUATIO
05F5..05FF ; UNASSIGNED # ..
0600..0604 ; DISALLOWED # ARAB NUM SIGN..ARAB SIGN SAM
0605 ; UNASSIGNED # ..
0606..060F ; FREE_PVAL # AR-IND CUBE ROOT..ARAB SIGN MISRA
0610..061A ; PVALID # ARAB SIGN SALLALLAHOU ALAYHE ..AR
061B ; FREE_PVAL # ARAB SEMICOLON
061C..061D ; UNASSIGNED # ..
061E..061F ; FREE_PVAL # ARAB TRIPLE DOT PUNCT MARK..ARAB Q
0620 ; UNASSIGNED #
0621..063F ; PVALID # ARAB LET HAMZA..ARAB LET FARSI YEH
0640 ; DISALLOWED # ARAB TATWEEL
0641..065F ; PVALID # ARAB LET FEH..ARAB WAVY HAMZA BEL
0660..0669 ; CONTEXTO # AR-IND DIG ZERO..AR-IND DIG
066A..066D ; FREE_PVAL # ARAB PCT SIGN..ARAB FIVE PNTED STA
066E..0674 ; PVALID # ARAB LET DOTLESS BEH..ARAB LET HIG
0675..0678 ; FREE_PVAL # ARAB LET HIGH HAMZA ALEF..ARAB LET
0679..06D3 ; PVALID # ARAB LET TTEH..ARAB LET YEH BARREE
06D4 ; FREE_PVAL # ARAB FULL STOP
06D5..06DC ; PVALID # ARAB LET AE..ARAB SM HIGH SEEN
06DD ; DISALLOWED # ARAB END OF AYAH
06DE ; FREE_PVAL # ARAB START OF RUB EL HIZB
06DF..06E8 ; PVALID # ARAB SM HIGH ROUNDED ZERO..ARAB SM
06E9 ; FREE_PVAL # ARAB PLACE OF SAJDAH
06EA..06EF ; PVALID # ARAB EMPTY CENTRE LOW STOP..ARAB LET
06F0..06F9 ; CONTEXTO # EXT AR-IND DIG ZERO..EXT A
06FA..06FF ; PVALID # ARAB LET SHEEN W DOT BEL..ARAB
0700..070D ; FREE_PVAL # SYR END OF PARA..SYR HARKLEAN AST
070E ; UNASSIGNED #
070F ; DISALLOWED # SYR ABBR MARK
0710..07B1 ; PVALID # SYR LET ALAPH..THAANA LET N
07B2..07BF ; UNASSIGNED # ..
07C0..07F5 ; PVALID # NKO DIG ZERO..NKO LOW TONE APOS
07F6..07F9 ; FREE_PVAL # NKO SYM OO DENNEN..NKO EXCLAMATI
07FA ; DISALLOWED # NKO LAJANYALAN
07FB..07FF ; UNASSIGNED # ..
0800..082D ; PVALID # SAMAR LET ALAF..SAMAR MARK NEQUDA
082E..082F ; UNASSIGNED # ..
0830..083E ; FREE_PVAL # SAMAR PUNCT NEQUDAA..SAMAR PUN
083F ; UNASSIGNED #
0840..085B ; PVALID # MANDAIC LET HALQA..MANDAIC GEM
085C..085D ; UNASSIGNED # ..
085E ; FREE_PVAL # MANDAIC PUNCTUATION
08A0..08AC ; PVALID # ARAB LET BEH W SM V BEL..ARAB
08AD..08E3 ; UNASSIGNED # ..
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08E4..08FE ; PVALID # ARAB CURLY FATHA..ARAB DAMMA W
08FF ; UNASSIGNED #
0900..0963 ; PVALID # DEVAN SIGN INV CANDRABINDU..DEVAN V
0964..0965 ; FREE_PVAL # DEVAN DANDA..DEVAN DOUBLE DANDA
0966..096F ; PVALID # DEVAN DIG ZERO..DEVAN DIG NINE
0970 ; FREE_PVAL # DEVAN ABBR SIGN
0971..097F ; PVALID # DEVAN SIGN HIGH SPACING DOT..DEVAN
0980 ; UNASSIGNED #
0981..0983 ; PVALID # BENG SIGN CANDRABINDU..BENG SIGN VISAR
0984 ; UNASSIGNED #
0985..098C ; PVALID # BENG LET A..BENG LET VOC L
098D..098E ; UNASSIGNED # ..
098F..0990 ; PVALID # BENG LET E..BENG LET AI
0991..0992 ; UNASSIGNED # ..
0993..09A8 ; PVALID # BENG LET O..BENG LET NA
09A9 ; UNASSIGNED #
09AA..09B0 ; PVALID # BENG LET PA..BENG LET RA
09B1 ; UNASSIGNED #
09B2 ; PVALID # BENG LET LA
09B3..09B5 ; UNASSIGNED # ..
09B6..09B9 ; PVALID # BENG LET SHA..BENG LET HA
09BA..09BB ; UNASSIGNED # ..
09BC..09C4 ; PVALID # BENG SIGN NUKTA..BENG VOW SIGN VOCAL
09C5..09C6 ; UNASSIGNED # ..
09C7..09C8 ; PVALID # BENG VOW SIGN E..BENG VOW SIGN AI
09C9..09CA ; UNASSIGNED # ..
09CB..09CE ; PVALID # BENG VOW SIGN O..BENG LET KHANDA
09CF..09D6 ; UNASSIGNED # ..
09D7 ; PVALID # BENG AU LEN MARK
09D8..09DB ; UNASSIGNED # ..
09DC..09DD ; PVALID # BENG LET RRA..BENG LET RHA
09DE ; UNASSIGNED #
09DF..09E3 ; PVALID # BENG LET YYA..BENG VOW SIG
09E4..09E5 ; UNASSIGNED # ..
09E6..09F1 ; PVALID # BENG DIG ZERO..BENG LET RA W L
09F2..09F3 ; FREE_PVAL # BENG RUPEE MARK..BENG RUPEE SIGN
09F4..09FB ; DISALLOWED # BENG CURR NUM ONE..BENG GANDA MARK
09FC..0A00 ; UNASSIGNED # ..
0A01..0A03 ; PVALID # GURMUKHI SIGN ADAK BINDI..GURMUKHI
0A04 ; UNASSIGNED #
0A05..0A0A ; PVALID # GURMUKHI LET A..GURMUKHI LET UU
0A0B..0A0E ; UNASSIGNED # ..
0A0F..0A10 ; PVALID # GURMUKHI LET EE..GURMUKHI LET AI
0A11..0A12 ; UNASSIGNED # ..
0A13..0A28 ; PVALID # GURMUKHI LET OO..GURMUKHI LET NA
0A29 ; UNASSIGNED #
0A2A..0A30 ; PVALID # GURMUKHI LET PA..GURMUKHI LET RA
0A31 ; UNASSIGNED #
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0A32..0A33 ; PVALID # GURMUKHI LET LA..GURMUKHI LET LLA
0A34 ; UNASSIGNED #
0A35.OA36 ; PVALID # GURMUKHI LET VA..GURMUKHI LET SHA
0A37 ; UNASSIGNED #
0A38..0A39 ; PVALID # GURMUKHI LET SA..GURMUKHI LET HA
0A3A..0A3B ; UNASSIGNED # ..
0A3C ; PVALID # GURMUKHI SIGN NUKTA
0A3D ; UNASSIGNED #
0A3E..0A42 ; PVALID # GURMUKHI VOW SIGN AA..GURMUKHI V
0A43..0A46 ; UNASSIGNED # ..
0A47..0A48 ; PVALID # GURMUKHI VOW SIGN EE..GURMUKHI V
0A49..0A4A ; UNASSIGNED # ..
0A4B..0A4D ; PVALID # GURMUKHI VOW SIGN OO..GURMUKHI S
0A4E..0A50 ; UNASSIGNED # ..
0A51 ; PVALID # GURMUKHI SIGN UDAAT
0A52..0A58 ; UNASSIGNED # ..
0A59..0A5B ; PVALID # GURMUKHI LET KHHA..GURMUKHI LET RRA
0A5D ; UNASSIGNED #
0A5E ; PVALID # GURMUKHI LET FA
0A5F..0A65 ; UNASSIGNED # ..
0A66..0A75 ; PVALID # GURMUKHI DIG ZERO..GURMUKHI SIGN YA
0A76..0A80 ; UNASSIGNED # ..
0A81..0A83 ; PVALID # GUJARATI SIGN CANDRABINDU..GUJARATI
0A84 ; UNASSIGNED #
0A85..0A8D ; PVALID # GUJARATI LET A..GUJARATI VOW CAND
0A8E ; UNASSIGNED #
0A8F..0A91 ; PVALID # GUJARATI LET E..GUJARATI VOW CAND
0A92 ; UNASSIGNED #
0A93..0AA8 ; PVALID # GUJARATI LET O..GUJARATI LET NA
0AA9 ; UNASSIGNED #
0AAA..0AB0 ; PVALID # GUJARATI LET PA..GUJARATI LET RA
0AB1 ; UNASSIGNED #
0AB2..0AB3 ; PVALID # GUJARATI LET LA..GUJARATI LET LLA
0AB4 ; UNASSIGNED #
0AB5..0AB9 ; PVALID # GUJARATI LET VA..GUJARATI LET HA
0ABA..0ABB ; UNASSIGNED # ..
0ABC..0AC5 ; PVALID # GUJARATI SIGN NUKTA..GUJARATI VOW
0AC6 ; UNASSIGNED #
0AC7..0AC9 ; PVALID # GUJARATI VOW SIGN E..GUJARATI VOW
0ACA ; UNASSIGNED #
0ACB..0ACD ; PVALID # GUJARATI VOW SIGN O..GUJARATI SIG
0ACE..0ACF ; UNASSIGNED # ..
0AD0 ; PVALID # GUJARATI OM
0AD1..0ADF ; UNASSIGNED # ..
0AE0..0AE3 ; PVALID # GUJARATI LET VOC RR..GUJARATI V
0AE4..0AE5 ; UNASSIGNED # ..
0AE6..0AEF ; PVALID # GUJARATI DIG ZERO..GUJARATI DIG NINE
0AF0 ; UNASSIGNED #
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0AF1 ; FREE_PVAL # GUJARATI RUPEE SIGN
0AF2..0B00 ; UNASSIGNED # ..
0B01..0B03 ; PVALID # ORIYA SIGN CANDRABINDU..ORIYA SIGN
0B04 ; UNASSIGNED #
0B05..0B0C ; PVALID # ORIYA LET A..ORIYA LET VOC L
0B0D..0B0E ; UNASSIGNED # ..
0B0F..0B10 ; PVALID # ORIYA LET E..ORIYA LET AI
0B11..0B12 ; UNASSIGNED # ..
0B13..0B28 ; PVALID # ORIYA LET O..ORIYA LET NA
0B29 ; UNASSIGNED #
0B2A..0B30 ; PVALID # ORIYA LET PA..ORIYA LET RA
0B31 ; UNASSIGNED #
0B32..0B33 ; PVALID # ORIYA LET LA..ORIYA LET LLA
0B34 ; UNASSIGNED #
0B35..0B39 ; PVALID # ORIYA LET VA..ORIYA LET HA
0B3A..0B3B ; UNASSIGNED # ..
0B3C..0B44 ; PVALID # ORIYA SIGN NUKTA..ORIYA VOW SIGN
0B45..0B46 ; UNASSIGNED # ..
0B47..0B48 ; PVALID # ORIYA VOW SIGN E..ORIYA VOW SIG
0B49..0B4A ; UNASSIGNED # ..
0B4B..0B4D ; PVALID # ORIYA VOW SIGN O..ORIYA SIGN VIRA
0B4E..0B55 ; UNASSIGNED # ..
0B56..0B57 ; PVALID # ORIYA AI LEN MARK..ORIYA AU LENG
0B58..0B5B ; UNASSIGNED # ..
0B5C..0B5D ; PVALID # ORIYA LET RRA..ORIYA LET RHA
0B5E ; UNASSIGNED #
0B5F..0B63 ; PVALID # ORIYA LET YYA..ORIYA VOW SIGN VOCA
0B64..0B65 ; UNASSIGNED # ..
0B66..0B6F ; PVALID # ORIYA DIG ZERO..ORIYA DIG NINE
0B70 ; FREE_PVAL # ORIYA ISSHAR
0B71 ; PVALID # ORIYA LET WA
0B72..0B77 ; FREE_PVAL # ORIYA FRACT ONE QUART..ORIYA FRACT
0B78..0B81 ; UNASSIGNED # ..
0B82..0B83 ; PVALID # TAMIL SIGN ANUSVARA..TAMIL SIGN VIS
0B84 ; UNASSIGNED #
0B85..0B8A ; PVALID # TAMIL LET A..TAMIL LET UU
0B8B..0B8D ; UNASSIGNED # ..
0B8E..0B90 ; PVALID # TAMIL LET E..TAMIL LET AI
0B91 ; UNASSIGNED #
0B92..0B95 ; PVALID # TAMIL LET O..TAMIL LET KA
0B96..0B98 ; UNASSIGNED # ..
0B99..0B9A ; PVALID # TAMIL LET NGA..TAMIL LET CA
0B9B ; UNASSIGNED #
0B9C ; PVALID # TAMIL LET JA
0B9D ; UNASSIGNED #
0B9E..0B9F ; PVALID # TAMIL LET NYA..TAMIL LET TTA
0BA0..0BA2 ; UNASSIGNED # ..
0BA3..0BA4 ; PVALID # TAMIL LET NNA..TAMIL LET TA
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0BA5..0BA7 ; UNASSIGNED # ..
0BA8..0BAA ; PVALID # TAMIL LET NA..TAMIL LET PA
0BAB..0BAD ; UNASSIGNED # ..
0BAE..0BB9 ; PVALID # TAMIL LET MA..TAMIL LET HA
0BBA..0BBD ; UNASSIGNED # ..
0BBE..0BC2 ; PVALID # TAMIL VOW SIGN AA..TAMIL VOW SI
0BC3..0BC5 ; UNASSIGNED # ..
0BC6..0BC8 ; PVALID # TAMIL VOW SIGN E..TAMIL VOW SIG
0BC9 ; UNASSIGNED #
0BCA..0BCD ; PVALID # TAMIL VOW SIGN O..TAMIL SIGN VIRA
0BCE..0BCF ; UNASSIGNED # ..
0BD0 ; PVALID # TAMIL OM
0BD1..0BD6 ; UNASSIGNED # ..
0BD7 ; PVALID # TAMIL AU LEN MARK
0BD8..0BE5 ; UNASSIGNED # ..
0BE6..0BEF ; PVALID # TAMIL DIG ZERO..TAMIL DIG NINE
0BF0..0BFA ; FREE_PVAL # TAMIL NUM TEN..TAMIL NUM SIGN
0BFB..0C00 ; UNASSIGNED # ..
0C01..0C03 ; PVALID # TELUGU SIGN CANDRABINDU..TELUGU SIG
0C04 ; UNASSIGNED #
0C05..0C0C ; PVALID # TELUGU LET A..TELUGU LET VOC L
0C0D ; UNASSIGNED #
0C0E..0C10 ; PVALID # TELUGU LET E..TELUGU LET AI
0C11 ; UNASSIGNED #
0C12..0C28 ; PVALID # TELUGU LET O..TELUGU LET NA
0C29 ; UNASSIGNED #
0C2A..0C33 ; PVALID # TELUGU LET PA..TELUGU LET LLA
0C34 ; UNASSIGNED #
0C35..0C39 ; PVALID # TELUGU LET VA..TELUGU LET HA
0C3A..0C3C ; UNASSIGNED # ..
0C3D..0C44 ; PVALID # TELUGU SIGN AVAGRAHA..TELUGU VOW SI
0C45 ; UNASSIGNED #
0C46..0C48 ; PVALID # TELUGU VOW SIGN E..TELUGU VOW SIGN
0C49 ; UNASSIGNED #
0C4A..0C4D ; PVALID # TELUGU VOW SIGN O..TELUGU SIGN VIRA
0C4E..0C54 ; UNASSIGNED # ..
0C55..0C56 ; PVALID # TELUGU LEN MARK..TELUGU AI LEN MARK
0C57 ; UNASSIGNED #
0C58..0C59 ; PVALID # TELUGU LET TSA..TELUGU LET DZA
0C5A..0C5F ; UNASSIGNED # ..
0C60..0C63 ; PVALID # TELUGU LET VOC RR..TELUGU VOW S
0C64..0C65 ; UNASSIGNED # ..
0C66..0C6F ; PVALID # TELUGU DIG ZERO..TELUGU DIG NINE
0C70..0C77 ; UNASSIGNED # ..
0C78..0C7E ; DISALLOWED # TELUGU FRACTION DIG ZERO FOR ODD PO
0C7F ; FREE_PVAL # TELUGU SIGN TUUMU
0C80..0C81 ; UNASSIGNED # ..
0C82..0C83 ; PVALID # KANNADA SIGN ANUSVARA..KANNADA SIGN
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0C84 ; UNASSIGNED #
0C85..0C8C ; PVALID # KANNADA LET A..KANNADA LET VOC L
0C8D ; UNASSIGNED #
0C8E..0C90 ; PVALID # KANNADA LET E..KANNADA LET AI
0C91 ; UNASSIGNED #
0C92..0CA8 ; PVALID # KANNADA LET O..KANNADA LET NA
0CA9 ; UNASSIGNED #
0CAA..0CB3 ; PVALID # KANNADA LET PA..KANNADA LET LLA
0CB4 ; UNASSIGNED #
0CB5..0CB9 ; PVALID # KANNADA LET VA..KANNADA LET HA
0CBA..0CBB ; UNASSIGNED # ..
0CBC..0CC4 ; PVALID # KANNADA SIGN NUKTA..KANNADA VOW SIG
0CC5 ; UNASSIGNED #
0CC6..0CC8 ; PVALID # KANNADA VOW SIGN E..KANNADA VOW SIG
0CC9 ; UNASSIGNED #
0CCA..0CCD ; PVALID # KANNADA VOW SIGN O..KANNADA SIGN VI
0CCE..0CD4 ; UNASSIGNED # ..
0CD5..0CD6 ; PVALID # KANNADA LEN MARK..KANNADA AI LEN MA
0CD7..0CDD ; UNASSIGNED # ..
0CDE ; PVALID # KANNADA LET FA
0CDF ; UNASSIGNED #
0CE0..0CE3 ; PVALID # KANNADA LET VOC RR..KANNADA VOW SIG
0CE4..0CE5 ; UNASSIGNED # ..
0CE6..0CEF ; PVALID # KANNADA DIG ZERO..KANNADA DIG NINE
0CF0 ; UNASSIGNED #
0CF1..0CF2 ; DISALLOWED # KANNADA SIGN JIHVAMULIYA..KANNADA S
0CF3..0D01 ; UNASSIGNED # ..
0D02..0D03 ; PVALID # MALAY SIGN ANUSVARA..MALAY SIGN VIS
0D04 ; UNASSIGNED #
0D05..0D0C ; PVALID # MALAY LET A..MALAY LET VOC
0D0D ; UNASSIGNED #
0D0E..0D10 ; PVALID # MALAY LET E..MALAY LET AI
0D11 ; UNASSIGNED #
0D12..0D3A ; PVALID # MALAY LET O..MALAY LET TTTA
0D3B..0D3C ; UNASSIGNED # ..
0D3D..0D44 ; PVALID # MALAY SIGN AVAGRAHA..MALAY VOW SIG
0D45 ; UNASSIGNED #
0D46..0D48 ; PVALID # MALAY VOW SIGN E..MALAY VOW SIGN
0D49 ; UNASSIGNED #
0D4A..0D4E ; PVALID # MALAY VOW SIGN O..MALAY LET DOT REP
0D4F..0D56 ; UNASSIGNED # ..
0D57 ; PVALID # MALAY AU LEN MARK
0D58..0D59 ; UNASSIGNED # ..
0D60..0D63 ; PVALID # MALAY LET VOC RR..MALAY VOW
0D64..0D65 ; UNASSIGNED # ..
0D66..0D6F ; PVALID # MALAY DIG ZERO..MALAY DIG NINE
0D70..0D75 ; FREE_PVAL # MALAY NUM TEN..MALAY FRACTION THR
0D76..0D78 ; UNASSIGNED # ..
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0D79 ; FREE_PVAL # MALAY DATE MARK
0D7A..0D7F ; PVALID # MALAY LET CHILLU NN..MALAY LET
0D80..0D81 ; UNASSIGNED # ..
0D82..0D83 ; PVALID # SINH SIGN ANUSVARAYA..SINH SIGN VIS
0D84 ; UNASSIGNED #
0D85..0D96 ; PVALID # SINH LET AYANNA..SINH LET AUYANN
0D97..0D99 ; UNASSIGNED # ..
0D9A..0DB1 ; PVALID # SINH LET ALPAPRAANA KAYANNA..SINH L
0DB2 ; UNASSIGNED #
0DB3..0DBB ; PVALID # SINH LET SANYAKA DAYANNA..SINH LETT
0DBC ; UNASSIGNED #
0DBD ; PVALID # SINH LET DANTAJA LAYANNA
0DBE..0DBF ; UNASSIGNED # ..
0DC0..0DC6 ; PVALID # SINH LET VAYANNA..SINH LET FAYAN
0DC7..0DC9 ; UNASSIGNED # ..
0DCA ; PVALID # SINH SIGN AL-LAKUNA
0DCB..0DCE ; UNASSIGNED # ..
0DCF..0DD4 ; PVALID # SINH VOW SIGN AELA-PILLA..SINH VOW
0DD5 ; UNASSIGNED #
0DD6 ; PVALID # SINH VOW SIGN DIGA PAA-PILLA
0DD7 ; UNASSIGNED #
0DD8..0DDF ; PVALID # SINH VOW SIGN GAETTA-PILLA..SINH VO
0DE0..0DF1 ; UNASSIGNED # ..
0DF2..0DF3 ; PVALID # SINH VOW SIGN DIGA GAETTA-PILLA..SI
0DF4 ; FREE_PVAL # SINH PUNCT KUNDDALIYA
0DF5..0E00 ; UNASSIGNED # ..
0E01..0E32 ; PVALID # THAI CHAR KO KAI..THAI CHAR SARA A
0E33 ; FREE_PVAL # THAI CHAR SARA AM
0E34..0E3A ; PVALID # THAI CHAR SARA I..THAI CHAR PHINTH
0E3B..0E3E ; UNASSIGNED # ..
0E3F ; FREE_PVAL # THAI CURRENCY SYM BAHT
0E40..0E4E ; PVALID # THAI CHAR SARA E..THAI CHAR YAMAKK
0E4F ; FREE_PVAL # THAI CHAR FONGMAN
0E50..0E59 ; PVALID # THAI DIG ZERO..THAI DIG NINE
0E5A..0E5B ; FREE_PVAL # THAI CHAR ANGKHANKHU..THAI CHAR KH
0E5C..0E80 ; UNASSIGNED # ..
0E81..0E82 ; PVALID # LAO LET KO..LAO LET KHO SUNG
0E83 ; UNASSIGNED #
0E84 ; PVALID # LAO LET KHO TAM
0E85..0E86 ; UNASSIGNED # ..
0E87..0E88 ; PVALID # LAO LET NGO..LAO LET CO
0E89 ; UNASSIGNED #
0E8A ; PVALID # LAO LET SO TAM
0E8B..0E8C ; UNASSIGNED # ..
0E8D ; PVALID # LAO LET NYO
0E8E..0E93 ; UNASSIGNED # ..
0E94..0E97 ; PVALID # LAO LET DO..LAO LET THO TAM
0E98 ; UNASSIGNED #
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0E99..0E9F ; PVALID # LAO LET NO..LAO LET FO SUNG
0EA0 ; UNASSIGNED #
0EA1..0EA3 ; PVALID # LAO LET MO..LAO LET LO LING
0EA4 ; UNASSIGNED #
0EA5 ; PVALID # LAO LET LO LOOT
0EA6 ; UNASSIGNED #
0EA7 ; PVALID # LAO LET WO
0EA8..0EA9 ; UNASSIGNED # ..