XML-Encryption Requirements

1. Introduction

The XML 1.0 Recommendation [XML] describes the syntax of a class of data objects called XML documents. There is interest in specification of XML syntax and processing used to encrypt digital content, including portions of an XML documents and protocol messages. This documents provides requirements for such an activity -- as well as provocations and alternative requirements.

2. Design Principles and Scope

1. The XML Encryption specification will describe how to a digitally encrypt a Web resource in general, and an XML document in particular.  {Imamura, SL}
   1. An XML Encryption can apply to a part or totality of an XML document.
      1. Granularity of encryption is limited to an element. {Imamura}
      2. Granularity of encryption includes attributes and content. {SL}
      3. Granularity of encryption includes any Information Set Item. {list-Reagle}
   2. Encryption can be recursive. {Imamura, SL}
2. The mechansims of encryption are simple: they describe how to encrypt/decrypt digital content, XML documents, and portions thereof. {Reagle}
   1. Only enough information necessary for decryption need be provided. {Reagle}
   2. The specification will not address the confidence or trust applications place in the provision of a key, nor mechanisms of key establishment.  {Reagle}
3. The only key structures that will be defined relate to those necessary decrypting opaque content. {Reagle}
   1. The specification will address both key-encrypting-keys and data keys. {Reagle}
   2. Other key structures are encouraged to be developed under a different namespace. {Reagle}
4. The specification will not address the expression of access control policies associated with portions of the XML document. {Reagle}
5. The specification  must use a pre-existing data models (e.g., Information Set) and canonicalization methods (e.g., Canonical XML) unless it can explitly justify the need for a new one. {Reagle}
6. Implementation/Design Philosophy
   1. @@Affect on deployed parsers.

3. Requirements

Signature Data Model and Syntax

1. An encrypted ojbect is XML. {Imamura, SL}
2. A valid XML instance, when encrypted and decrypted must still be valid. {Reagle}
3. The XML Encryption data structures will be predicated on: {Reagle}
   1. the RDFS schema within the Information Set specification [Infoset]
   2. [XSet]
   3. ...
4. An XML Encryption application must be able to use and understand {Reagle}
   1. XML-namespaces [XML-namespaces].
5. XML Encryptions can be applied to any Web resource -- including non-XML content.    {Imamura, SL}
6. Encrypted objects are first class objects themselves and consequently can be referenced and signed. {Reagle}
7. Algorithm Identification
   1. Whenever possible, any resource or algorithm is a first class object, and identified by a URI.   {Imamura, SL}

Cryptography

1. The solution shall should work with arbitrary encryption algorithms, including symmetric and asymmetric keys schemes as well as dynamic negotiation of keying material. {Imamura, SL}
   1. The specification will not address key establishment  methods. {Reagle}
2. The specification must specify at least one mandatory to implement canonicalization, hash, and encryption algorithm. {Reagle}

Canonicalization

1. ...

Processing

1. ...

Misc

1. @@Where did we stand on the issue of email headers encryptor/recipient?

Coordination

The XML Encryption specification should meet the requirements of or work with the following applications:

1. [XML Protocols]
2. [XML Signature]

To ensure the above requirements are adequately addressed, the XML Encryption specification must be reviewed by a designated member of the following communities:

1. XML Schema Working Group {Reagle}
2. XML Core Working Group {Reagle}
3. XML Protocol Working Group {Reagle}
4. Internationalization Interest Group {Reagle}

4. References

Imamura

Another proposal of XML Encryption, Takeshi Imamura (Mon, Aug 14 2000)

C2000

Crypto 2000 XML Encryption BoF (minutes). Santa Barbara. August 24 .

DOM

Document Object Model Core, Level 3. Arnaud Le Hors. W3C Working Draft.
http://www.w3.org/TR/DOM-Level-3-Core/core.html

List

XML Encryption List (an unmoderated and unchartered publis list).

InfoSet

XML Information Set, W3C Working Draft. John Cowan.
http://www.w3.org/TR/xml-infoset.

SL

XML Encryption strawman proposal Ed Simon and Brian LaMacchia (Wed, Aug 09 2000)

XML

Extensible Markup Language (XML) 1.0 Recommendation. T. Bray, J. Paoli, C. M. Sperberg-McQueen. February 1998.

http://www.w3.org/TR/1998/REC-xml-19980210

XML-C14N

Canonical XML. Working Draft. J. Boyer. September 2000.

http://www.w3.org/TR/2000/WD-xml-c14n-20000907

XML-ns

Namespaces in XML Recommendation. T. Bray, D. Hollander, A. Layman. Janaury 1999.

http://www.w3.org/TR/1999/REC-xml-names-19990114

XML-schema

XML Schema Part 1: Structures Working Draft. D. Beech, M. Maloney, N. Mendelshohn. April 2000.

http://www.w3.org/TR/2000/WD-xmlschema-1-20000407/
XML Schema Part 2: Datatypes Working Draft. P. Biron, A. Malhotra. April 2000.

http://www.w3.org/TR/2000/WD-xmlschema-2-20000407/

XMLDSIG

XML-Signature Syntax and Processing. Working Draft. D. Eastlake, J. Reagle, and D. Solo.
http://www.w3.org/TR/2000/WD-xmldsig-core-20000918/

XSet

Full Fidelity Information Set Representation. Jonathan Borden. XML-Dev

http://lists.xml.org/archives/xml-dev/200008/msg00239.html

URI

RFC2396. Uniform Resource Identifiers (URI): Generic Syntax. T. Berners-Lee, R. Fielding, L. Masinter. August 1998
http://www.ietf.org/rfc/rfc2396.txt