Traceable Anonymous Certificate
RFC 5636

[Ballot comment]
I'm pleased to see Experimental status being used for this work.

The only thing I might ask you think about is some descriprition of the scope of the Experiment and a note on whether there is a plan to return at some point (if the results are favorable) to do further work.

  (1.a) Who is the Document Shepherd for this document?
          Has the Document Shepherd personally reviewed this version of
          the document and, in particular, does he or she believe this
          version is ready for forwarding to the IESG for publication?

Stefan Santesson is the document shepherd for this document, has personally reviewed this version of the document and believes this version is ready for forwarding to the IESG for publication.

    (1.b) Has the document had adequate review both from key WG members
          and from key non-WG members? Does the Document Shepherd have
          any concerns about the depth or breadth of the reviews that
          have been performed?

The document has received adequate review from both key WG members and key non-WG members.  There are no concerns regarding the depth or breath of the reviews that have been performed.

    (1.c) Does the Document Shepherd have concerns that the document
          needs more review from a particular or broader perspective,
          e.g., security, operational complexity, someone familiar with
          AAA, internationalization or XML?

No.

    (1.d) Does the Document Shepherd have any specific concerns or
          issues with this document that the Responsible Area Director
          and/or the IESG should be aware of? For example, perhaps he
          or she is uncomfortable with certain parts of the document, or
          has concerns whether there really is a need for it. In any
          event, if the WG has discussed those issues and has indicated
          that it still wishes to advance the document, detail those
          concerns here. Has an IPR disclosure related to this document
          been filed? If so, please include a reference to the
          disclosure and summarize the WG discussion and conclusion on
          this issue.

There are no specific concerns to highlight to the AD or IESG. No IPR disclosures have been filed related to this document.

    (1.e) How solid is the WG consensus behind this document? Does it
          represent the strong concurrence of a few individuals, with
          others being silent, or does the WG as a whole understand and
          agree with it?

This document has reached rough WG consensus after considerable debate over the last 18 months. It is targeted at Experimental status. This work did not attract much interest from most WG members initially. It addresses a PKI niche, which some WG members didn't think would ever be of commercial interest. The document authors were Korean and they had considerable trouble expressing their ideas in writing, and in a suitable style for an IETF standard. Steve Kent, my co-chair, agreed to become a co-author and he re-wrote the document and has coordinated subsequent revisions. Two WG members provided extensive reviews of the I-D, which resulted in a number of changes to address technical details. The version that entered WGLC triggered comments from a few WG members. Changes were made to address several of these comments, but a suggestion to make a substantial design change was rejected. Two WG members raised concerns whether the split-signature technology employed here adds enough security to merit the increased complexity. However, the principle authors work for KISA, the Korean Information Security Agency that accredits CAs in that country. Their judgment that this is a reasonable tradeoff is enough to merit progression as experimental document. The real proof of the document's value will be decided based on adoption by CAs, something the KISA authors say will happen (at least in their country).

    (1.f) Has anyone threatened an appeal or otherwise indicated extreme
          discontent? If so, please summarize the areas of conflict in
        separate email messages to the Responsible Area Director. (It
          should be in a separate email because this questionnaire is
          entered into the ID Tracker.)

No.

    (1.g) Has the Document Shepherd personally verified that the
          document satisfies all ID nits? (See
        http://www.ietf.org/ID-Checklist.html and
        http://tools.ietf.org/tools/idnits/). Boilerplate checks are
          not enough; this check needs to be thorough. Has the document
          met all formal review criteria it needs to, such as the MIB
          Doctor, media type and URI type reviews?

Yes. The document contains a few minor issues such as four too long lines, some double spacing and a few unused informative references. These minor issues can be fixed on next update or in the RFC editor process.

    (1.h) Has the document split its references into normative and
          informative? Are there normative references to documents that
          are not ready for advancement or are otherwise in an unclear
          state? If such normative references exist, what is the
          strategy for their completion? Are there normative references
          that are downward references, as described in [RFC3967]? If
          so, list these downward references to support the Area
          Director in the Last Call procedure for them [RFC3967].

References have been split into normative and informative sections.

    (1.i) Has the Document Shepherd verified that the document IANA
          consideration section exists and is consistent with the body
          of the document? If the document specifies protocol
          extensions, are reservations requested in appropriate IANA
          registries? Are the IANA registries clearly identified? If
          the document creates a new registry, does it define the
          proposed initial contents of the registry and an allocation
          procedure for future registrations? Does it suggest a
          reasonable name for the new registry? See [RFC5226]. If the
          document describes an Expert Review process has Shepherd
          conferred with the Responsible Area Director so that the IESG
          can appoint the needed Expert during the IESG Evaluation?

The I-D has an IANA Considerations section that indicates there are no IANA considerations.

    (1.j) Has the Document Shepherd verified that sections of the
          document that are written in a formal language, such as XML
          code, BNF rules, MIB definitions, etc., validate correctly in
          an automated checker?

There is an ASN.1 module in Appendix A that appears to be correct, and has been reviewed by Jim Schaad, but I have not personally tried to compile it.

    (1.k) The IESG approval announcement includes a Document
          Announcement Write-Up. Please provide such a Document
          Announcement Write-Up? Recent examples can be found in the
          "Action" announcements for approved documents. The approval
          announcement contains the following sections:
          Technical Summary
            Relevant content can frequently be found in the abstract
            and/or introduction of the document. If not, this may be
            an indication that there are deficiencies in the abstract
            or introduction.
          Working Group Summary
            Was there anything in WG process that is worth noting? For
            example, was there controversy about particular points or
            were there decisions where the consensus was particularly
            rough?
          Document Quality
            Are there existing implementations of the protocol? Have a
            significant number of vendors indicated their plan to
            implement the specification? Are there any reviewers that
            merit special mention as having done a thorough review,
            e.g., one that resulted in important changes or a
            conclusion that the document had no substantive issues? If
            there was a MIB Doctor, Media Type or other expert review,
            what was its course (briefly)? In the case of a Media Type
            review, on what date was the request posted?

Technical Summary

  This document describes a model for issuing X.509 certificates in which the certificates do not contain the "true" name of the user, and thus provide some level of anonymity. Traceable Anonymous Certificates (TACs) are issued by a CA that is divided into two parts. One part verifies and records the identity of the user to whom the certificate is issued, and the other issues the certificate to the user but does not know the user's identity.  The certificates issued under the TAC model are intended primary for use in web access (and not in applications such as e-mail). The model allows an aggrieved party to request that a TAC CA divulge the identity of a user who has abused the anonymity offered by the certificate. (Details of what constitutes abuse by a user are outside the scope of the document and are established by TAC CA via a Certification Policy.) To void the anonymity offered by the two-arty issuance procedure, both parts of the CA collaborate using a protocol defined in the document.  The current version of the model supports only RSA-based security protocols between the two parts of the TAC CA, although the user's certificate may contain a public key for any algorithm.


Working Group Summary

See the answer to 1.e above for a history of the document's progress and the residual controversy.

Document Quality

There are no know implementations at this time, which is not surprising for a document targeted at Experimental status. However, the KISA staff who are the principle authors have indicated that they anticipate at least one commercial TAC CA (in South Korea) will be forthcoming after an RFC is published. An organization that chooses to implement the model described here will be a CA service provider, not a product vendor per se.