Using Trust Anchor Constraints during Certification Path Processing
RFC 5937

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Internet Engineering Task Force (IETF)                        S. Ashmore
Request for Comments: 5937                      National Security Agency
Category: Informational                                       C. Wallace
ISSN: 2070-1721                                       Cygnacom Solutions
                                                             August 2010

  Using Trust Anchor Constraints during Certification Path Processing

Abstract

   This document describes how to use information associated with a
   trust anchor public key when validating certification paths.  This
   information can be used to constrain the usage of a trust anchor.
   Typically, constraints are used to limit the certificate policies and
   names that can appear in certification paths validated using a trust
   anchor.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5937.

Ashmore & Wallace             Informational                     [Page 1]
RFC 5937             Using Trust Anchor Constraints          August 2010

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1. Introduction ....................................................3
      1.1. Terminology ................................................3
   2. Identifying Trust Anchor Constraints ............................3
   3. Using Trust Anchor Constraints during Certification Path
      Processing ......................................................4
      3.1. Inputs .....................................................4
      3.2. Initialization .............................................4
      3.3. Basic Certificate Processing ...............................6
      3.4. Preparation for Certificate i+1 ............................6
      3.5. Wrap-Up Procedure ..........................................6
   4. Relationship to RFC 5280 ........................................6
   5. Security Considerations .........................................7
   6. References ......................................................7
      6.1. Normative References .......................................7
      6.2. Informative References .....................................7

Ashmore & Wallace             Informational                     [Page 2]
RFC 5937             Using Trust Anchor Constraints          August 2010

1.  Introduction

   Trust anchors are widely used to verify digital signatures and
   validate certification paths [RFC5280] [X.509].  They are required
   when validating certification paths.  The Trust Anchor Format (TAF)
   specification [RFC5914] defines a means for limiting the scope in
   which a trust anchor may be used.  [RFC5280] describes how to
   validate a certification path.  The algorithm requires processing the
   name and key from a trust anchor.  Usage of other information,
   including enforcement of constraints, is permitted but not required,
   and the processing rules are not specified (see Section 6.2 of
   RFC 5280).

   This document defines a mechanism to identify constraints that should