MicroID
draft-miller-microid-01

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Copyright Notice

Copyright © The IETF Trust (2007).

Abstract

This specification defines MicroID, a lightweight identity technology that enables the creation of a portable identity token based on any two Uniform Resource Identifiers.

Table of Contents

1.  Introduction
    1.1.  Overview
    1.2.  Terminology
    1.3.  Discussion Venue
    1.4.  Acknowledgements
2.  Format
3.  Generation
4.  Processing
5.  Meaning
    5.1.  Overview
    5.2.  Generating Applications
    5.3.  Using Technologies
6.  Internationalization Considerations
7.  Security Considerations
8.  References
    8.1.  Normative References
    8.2.  Informative References
Appendix A.  Legacy Support
Appendix B.  Copying Conditions
§  Authors' Addresses
§  Intellectual Property and Copyright Statements

1.  Introduction

1.1.  Overview

MicroID is a lightweight identity technology that enables the creation of a portable identity token from any two Uniform Resource Identifiers [URI] (Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax,” January 2005.).

Such identity tokens are desirable because they:

• Enable individuals to assert ownership over information published and reputation earned on the Internet in a granular manner.
• Enable service providers to "stamp" information and reputation based on a validated URI associated with an individual who uses the service.

1.2.  Terminology

The following keywords as used in this document are to be interpreted as described in [TERMS] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.): "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".

1.3.  Discussion Venue

The preferred discussion forum for this specification is the MicroID mailing list; subscription information is located at <http://lists.ibiblio.org/mailman/listinfo/microid> and the mailing list archives are located at <http://lists.ibiblio.org/pipermail/microid/>.

1.4.  Acknowledgements

Thanks to James Cridland, Yaniv Golan, David Koblas, Paco Nathan, Will Norris, Evan Prodromou, Chris Roos, Terrell Russell, Eran Sandler, and Brian Suda for their feedback.

2.  Format

The syntax for a MicroID is defined as follows, using the Augmented Backus-Naur Form specified in [ABNF] (Crocker, D. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF,” October 2005.).

microid = inputs ":" algo ":" hash
inputs  = scheme "+" scheme
scheme  = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )
          ; a URI scheme name (e.g., mailto)
algo    = ALPHA *( ALPHA / DIGIT )
          ; the short name of a hashing
          ; algorithm (e.g., sha256),
hash    = *( ALPHA / DIGIT )
          ; a hash of the URIs for both entities

Note: If the URI scheme name includes the "+" character (which is allowed by [URI] (Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax,” January 2005.) but not in common use), that character MUST be escaped to %2B.

Note: The algorithm names should be as registered with the IANA in the Hash Function Textual Names registry located at <http://www.iana.org/assignments/hash-function-text-names>, but may exclude the "-" character (e.g., "sha1" rather than "sha-1").

Note: See the Legacy Support (Legacy Support) section of this document for information regarding the original MicroID format.

3.  Generation

The method for generating the hash is:

hash = algo(
            algo(EntityURI)
            +
            algo(EntityURI)
           )

The "algo" MAY be any recognized hashing algorithm, such as those defined in [SHA] (National Institute of Standards and Technology, “Secure Hash Standard,” August 2002.). Support for the sha1 and sha256 algorithms is REQUIRED for interoperability. The output MUST be in hexadecimal (not base64) format. The same algorithm MUST be used for all hashing functions when generating a given MicroID.

The "EntityURI" MAY conform to any URI scheme, such as [HTTP] (Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, “Hypertext Transfer Protocol -- HTTP/1.1,” June 1999.), , [SIP] (Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, “SIP: Session Initiation Protocol,” June 2002.), or [XMPP] (Saint-Andre, P., “Internationalized Resource Identifiers (IRIs) and Uniform Resource Identifiers (URIs) for the Extensible Messaging and Presence Protocol (XMPP),” August 2006.).

As an example, consider the following inputs, from which a MicroID is generated using the sha1 algorithm:

• The first entity is an individual identified by an XMPP URI of "xmpp:".
• The second entity is a service provider identified by an HTTP URI of "https://www.xmpp.net/".

The hash is generated as follows (note: the line break in the third example is included only for the sake of readability):

sha1(
     sha1(xmpp:)
     +
     sha1(https://www.xmpp.net/)
    )

sha1(
     afa6353518f818af2f036da336c3097dedc00dee
     +
     3115de01ebfa34a34314060b5f30038b0fa359f8
    )

sha1(
afa6353518f818af2f036da336c3097dedc00dee
3115de01ebfa34a34314060b5f30038b0fa359f8
    )

6196ea6709be2a4cbdf2bc0cfaeac491f2fb8921

Thus in accordance with the format previously described the issued MicroID is:

xmpp+https:sha1:6196ea6709be2a4cbdf2bc0cfaeac491f2fb8921

4.  Processing

A processing application MAY use only the hash portion of the MicroID for comparison purposes. An implementation SHOULD be liberal in accepting MicroIDs that conform to the legacy format; for details, see the Legacy Support (Legacy Support) section of this document.

5.  Meaning

5.1.  Overview

By itself, a MicroID has no inherent meaning, since it is simply a string created from two URIs. Any entity can generate a MicroID even if it has not verified the identity of the resources associated with one or both URIs. Furthermore, a MicroID is easily copied by an entity that did not generate it. Finally, a MicroID is not digitally signed by the entity that generated it and therefore cannot be cryptographically associated with the generating entity.

Therefore it may be wondered: what is the meaning of a MicroID? The answer is: any meaning imputed to a MicroID results from the context in which it is used. That context includes the nature of the generating application and the nature of the using technology.

Some possible generating applications and using technologies are described in the following sections. We use the following terms to describe the parties involved in the generation and processing of a MicroID:

• Consumer -- Any party that reads a MicroID issued by an Issuer (in other identity systems, a consumer is sometimes called a relying party).
• Entity -- Either party identified by a URI or IRI that is used to construct a MicroID.
• Individual -- An entity that generates information or earns reputation.
• Issuer -- The party that generates a MicroID. The issuer can be a third party and need not be an entity.
• Service Provider -- An entity that is responsible for hosting information or reputation; a service provider may or may not be an issuer.

A MicroID should be generated by an issuer, not by an individual. The issuer may be the service provider that hosts the information about, content created by, or reputation earned by an individual, or it may be a third party trusted by both the individual and the service provider.

An issuer should not generate a MicroID until it has verified that the individual or service provider has control over a given entity URI. Methods for such verification are out of scope for this specification and may vary according to local service policies and the URI scheme in question.

The first entity URI should be that of the individual and the second EntityURI should be that of the service provider. Any given entity URI may have meaning above and beyond that encapsulated in the relevant URI scheme; for example, the HTTP URI for an individual could be hosted by an OpenID service (see <http://openid.net/>). However, MicroID places no restrictions on the semantics of a given entity URI.

5.2.  Generating Applications

5.2.1.  Service Provider

It is envisioned that one common deployment scenario will be that of a service provider "stamping" information or reputation that is hosted by the service provider on behalf of individuals. In this architecture, the service provider is both the issuer and one of the entities, where the other entity is an individual.

     +--------+
     | Entity |
     +--------+
         |
         | registration
         |
+-------------------+
| Service Provider  |
| (Entity + Issuer) |
+-------------------+
         |
         | issuance
         |
      MicroID

Whether a given consumer imputes meaning to the MicroID in this scenario depends on the consumer's relationship to the service provider, whether the consumer has some trust in the information presented by the service provider, etc.

5.2.2.  Third Party as Issuer

Another scenario is that in which the MicroID is issued by a trusted third party (e.g., a part with which both a service provider and individual have registered). In this architecture, the service provider is merely one of the entities.

+--------+    +------------------+
| Entity |    | Service Provider |
+--------+    +------------------+
    |                 |
    |                 |
    +-----------------+
           |
           | registration
           |
       +--------+
       | Issuer |
       +--------+
           |
           | issuance
           |
        MicroID

Whether a given consumer imputes meaning to the MicroID in this scenario depends on the consumer's relationship to the third part, whether the consumer has some trust in the information presented by the third party, whether the consumer is one of the entities, etc.

5.3.  Using Technologies

This specification does not limit the technologies that might make use of MicroIDs, and future versions of this specification might describe a wide range of such uses. Here we describe two such uses.

Note: The scope of information (e.g., markup) covered by a MicroID depends on the nature of the using technology and must be defined separately by each using technology.

5.3.1.  HTML Class Attribute

One possible use is to include a MicroID in the HyperText Markup Language [HTML] (Jacobs, I., Raggett, D., and A. Hors, “HTML 4.01 Specification,” December 1999.) class attribute. The recommended format is to prepend the MicroID itself with the string "microid-", as shown in the following example:

<p class='microid-xmpp+https:sha1:
6196ea6709be2a4cbdf2bc0cfaeac491f2fb8921'>
mycontent</p>

In this usage, the scope of the MicroID is all information contained within the element that possesses the class attribute, whether that information is represented as attributes, character data, or child elements. However, any given child element may itself possess a class attribute specifying a MicroID that overrides the content claim asserted by the parent element. In all cases, the relevant claim is always that of the nearest containing element in the hierarchy.

A MicroID can be used on its own to mark content as created by a certain individual (e.g., a comment made on a web forum):

<div class='
microid-xmpp+https:sha1:6196ea6709be2a4cbdf2bc0cfaeac491f2fb8921'>
  <p>This is a great idea!</p>
</div>

A MicroID can be also used in concert with other lightweight identity technologies such as the rel='me' value defined by XHTML Friends Network (XFN) as specified at <http://gmpg.org/xfn/11>:

<div class='
  microid-xmpp+https:sha1:6196ea6709be2a4cbdf2bc0cfaeac491f2fb8921'>
  <p>This is a great idea!</p>
  <p>--<a rel='me'
          href='http://2idi.com/contact/=stpeter'>
          stpeter</a></p>
</div>

5.3.2.  HTML Meta Data

Another possible use is in meta data about an [HTML] (Jacobs, I., Raggett, D., and A. Hors, “HTML 4.01 Specification,” December 1999.) file (e.g., to signify that a given web page is created by, owned by, or about a given Individual). This is done by including a <meta/> tag whose 'name' attribute is "microid" and whose 'content' attribute specifies the MicroID, as shown in the following example:

<meta
  name='microid'
  content='xmpp+https:sha1:6196ea6709be2a4cbdf2bc0cfaeac491f2fb8921'/>

In this usage, the scope of the MicroID is the page itself. However, the whole-page claim represented in the META tag can be overridden by claims represented in class attributes possessed by elements within the HTML body.

A file MAY contain multiple META tags with a name of "microid" (e.g., to claim ownership by multiple authors or to represent multiple identities associated with the same individual).

6.  Internationalization Considerations

A MicroID SHOULD be constructed using two Uniform Resource Identifiers [URI] (Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax,” January 2005.) but one or both inputs MAY instead be an Internationalized Resource Identifier [IRI] (Duerst, M. and M. Suignard, “Internationalized Resource Identifiers (IRIs),” January 2005.).

7.  Security Considerations

MicroID is a technology for identifying the ownership or authorship of information on the Internet. It is not a mechanism for authentication, authorization, security, or encryption. Use of MicroID technology results only in weak verification of identities (if any). MicroID may be susceptible to [DNS] (Mockapetris, P., “Domain names - implementation and specification,” November 1987.) poisoning attacks unless [DNSSEC] (Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, “DNS Security Introduction and Requirements,” March 2005.) is used, since most URIs depend on DNS.

8.  References

8.1. Normative References

8.2. Informative References

Appendix A.  Legacy Support

MicroID originally assumed the use of sha1 as the hashing algorithm and did not specify the schemes of the EntityURI inputs, resulting in the following format:

microid = hash
hash    = *( ALPHA / DIGIT )
          ; a hash of the URIs for both entities

For example, using the same inputs as shown in the body of this specification, the MicroID in legacy format would be:

6196ea6709be2a4cbdf2bc0cfaeac491f2fb8921

An implementation MUST generate MicroIDs in the format specified in the Format (Format) section of this document, but SHOULD process MicroIDs generated using the legacy format for the sake of backward compatibility.

Appendix B.  Copying Conditions

The Contributors grant third parties the irrevocable right to copy, use and distribute the Contribution, with or without modification, in any medium, without royalty, provided that, unless separate permission is granted, redistributed modified works:

1. do not contain misleading author, version, name of work, or endorsement information, and
2. do not claim endorsement of the modified work by the Contributors, or any organizations the Contributors belong to, the Internet Engineering Task Force (IETF), Internet Research Task Force (IRTF), Internet Engineering Steering Group (IESG), Internet Architecture Board (IAB), Internet Assigned Numbers Authority (IANA), Internet Society (ISOC), Request For Comments (RFC) Editor, or any combination or variation of such terms (including without limitation the IETF "4 diamonds" logo), or any terms that are confusingly similar thereto, and
3. remove any claims of status as an Internet Standard, including without limitation removing the RFC boilerplate.

The IETF suggests that any citation or excerpt of unmodified text reference the RFC or other document from which the text is derived.

Authors' Addresses

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