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This specification defines MicroID, a lightweight identity technology that enables the creation of a portable identity token based on any two Uniform Resource Identifiers.
1.3. Discussion Venue
5.2. Generating Applications
5.3. Using Technologies
6. Internationalization Considerations
7. Security Considerations
8.1. Normative References
8.2. Informative References
Appendix A. Legacy Support
Appendix B. Copying Conditions
§ Authors' Addresses
§ Intellectual Property and Copyright Statements
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:
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".
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/>.
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.
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.
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.), [MAILTO] (Hoffman, P., Masinter, L., and J. Zawinski, “The mailto URL scheme,” July 1998.), [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 hash is generated as follows (note: the line break in the third example is included only for the sake of readability):
sha1( sha1(xmpp:email@example.com) + sha1(https://www.xmpp.net/) ) sha1( afa6353518f818af2f036da336c3097dedc00dee + 3115de01ebfa34a34314060b5f30038b0fa359f8 ) sha1( afa6353518f818af2f036da336c3097dedc00dee 3115de01ebfa34a34314060b5f30038b0fa359f8 ) 6196ea6709be2a4cbdf2bc0cfaeac491f2fb8921
Thus in accordance with the format previously described the issued MicroID is:
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.
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:
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.
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.
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.
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.
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>
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).
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.).
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.
|[ABNF]||Crocker, D. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF,” RFC 4234, October 2005 (TXT).|
|[SHA]||National Institute of Standards and Technology, “Secure Hash Standard,” FIPS PUB 180-2, August 2002.|
|[TERMS]||Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” BCP 14, RFC 2119, March 1997 (TXT, HTML, XML).|
|[URI]||Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax,” STD 66, RFC 3986, January 2005 (TXT, HTML, XML).|
|[DNS]||Mockapetris, P., “Domain names - implementation and specification,” STD 13, RFC 1035, November 1987 (TXT).|
|[DNSSEC]||Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, “DNS Security Introduction and Requirements,” RFC 4033, March 2005 (TXT).|
|[HTML]||Jacobs, I., Raggett, D., and A. Hors, “HTML 4.01 Specification,” World Wide Web Consortium Recommendation REC-html401-19991224, December 1999 (HTML).|
|[HTTP]||Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, “Hypertext Transfer Protocol -- HTTP/1.1,” RFC 2616, June 1999 (TXT, PS, PDF, HTML, XML).|
|[IRI]||Duerst, M. and M. Suignard, “Internationalized Resource Identifiers (IRIs),” RFC 3987, January 2005 (TXT).|
|[MAILTO]||Hoffman, P., Masinter, L., and J. Zawinski, “The mailto URL scheme,” RFC 2368, July 1998 (TXT, HTML, XML).|
|[SIP]||Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, “SIP: Session Initiation Protocol,” RFC 3261, June 2002 (TXT).|
|[XMPP]||Saint-Andre, P., “Internationalized Resource Identifiers (IRIs) and Uniform Resource Identifiers (URIs) for the Extensible Messaging and Presence Protocol (XMPP),” RFC 4622, August 2006 (TXT).|
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:
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.
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