Re: I-D ACTION:draft-ietf-smime-escertid-00.txt


Peter Gutmann wrote:

"Denis Pinkas" <denis(_dot_)pinkas(_at_)bull(_dot_)net> writes:

The current ASN.1 in RFC 2634 is:

 ESSCertID ::=  SEQUENCE {
      certHash                 Hash,
      issuerSerial             IssuerSerial OPTIONAL
 }

The proposal from draft-ietf-smime-escertid-00.txt is:

    ESSCertIDEx ::=  SEQUENCE {
         certHash                 Hash,
         hashAlg                  AlgorithmIdentifier DEFAULT {id-sha256},
         issuerSerial             IssuerSerial OPTIONAL
    }

The proposal made on the PKIX mailing list is:

ESSCertIDv2 ::= SEQUENCE {
  certHash         OCTET STRING,
  issuerSerial     IssuerSerial,
  hashAlgorithm    AlgorithmIdentifier DEFAULT { sha-1 }

The advantage of the last proposal is backward compatibility with the
existing structure.



No it isn't, you've lost the 'OPTIONAL' on issuerSerial, making it non-
backwards-compatible.  If you want it to have the properties you claim it has,
you'd need:

ESSCertIDv2 ::= SEQUENCE {
    certHash         Hash,
    issuerSerial     IssuerSerial OPTIONAL,
    hashAlgorithm    AlgorithmIdentifier DEFAULT { sha-1 }


Well passing through those structures caught my attention.

Aren't they ambiguous and could possibly be rejected by ASN1 compilers
or parsers?

My reason being that the presence of DEFAULT/OPTIONAL fields is decided
by the tag and both IssuerSerial and AlgorithmIdentifier both have a
SEQUENCE tag.

Steve.
-- 
Dr Stephen N. Henson.
Core developer of the   OpenSSL project: http://www.openssl.org/
Freelance consultant see: http://www.drh-consultancy.co.uk/
Email: shenson(_at_)drh-consultancy(_dot_)co(_dot_)uk, PGP key: via homepage.