- From: Thomas Maslen <maslen@dstc.edu.au>
- Date: Mon, 04 Jun 2001 12:53:07 +1000
- To: w3c-ietf-xmldsig@w3.org
Section 6.3.1 says
The HMAC algorithm (RFC2104 [HMAC]) takes the truncation length in
bits as a parameter; if the parameter is not specified then all the
bits of the hash are output.
Neither this nor RFC 2104 specifies the behaviour when the truncation length
is not a multiple of 8. RFC 2104 doesn't need to specify this because it's
not dealing with wire formats, but the xmldsig spec probably should.
Options that I can think of are:
(1) Specify a placement (MSB or LSB) for the leftover bits and a value
for the unused bits; my guess is that the most reasonable choice
is MSB and 0, i.e. consistent with ASN.1 BIT STRING.
(2) Require that HMACOutputLength be a multiple of 8.
Of these, I would prefer (2).
Thomas Maslen
DSTC
Received on Sunday, 3 June 2001 22:53:17 UTC