On Fri, 2007-03-02 at 06:41 -0800, Hallam-Baker, Phillip wrote: > Since we are drafting a requirement here we do not need to give the > explanation in the detail given on the list. > > The signing policy statement MUST be capable of fully describing a > signing practice in which multiple signatures are always provided such > that the policy is of utility to any verifier is capable of verifying > any of the signatures that are always provided. > > Such a mechanism MUST NOT > * Require the verifier to perform any additional DNS lookups. > * Require duplication of configuration data > * In particular not require the policy record to provide for the > description of any cryptographic or cannonicalization algorithm
Without being able to specify the critical elements that must be found within a superseding signature, there is no assurance that a spoofed and unsupported signature has not replaced the stronger algorithm. Spoofing could be accomplished by simply listing a different query mechanism. > Rationale: The ability to specify multiple signatures is necessary in > order to permit orderly transitions to new cryptographic and > canonicalization algorithms. Unless the policy language is not > sufficiently expressive to allow the signer to describe the actual > signature practice in this case there is an opportunity for an > attacker to exploit the fact that there are verifiers that do not yet > support the new algorithm. Perhaps I do not understand your last point then. -Doug _______________________________________________ NOTE WELL: This list operates according to http://mipassoc.org/dkim/ietf-list-rules.html
