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In message <[email protected]>, John Levine
<[email protected]> writes
>I'd change the spec to say signers MUST implement SHA256 and SHOULD implement
>SHA512.
>Verifiers MUST implement both of them because even though there's no SHA512
>signatures,
>you're allowed to use SHA512 to hash Message-Instance and per a note later on,
>the
>point is to be able to test hash algorithm migration.
I don't see an issue with that ... as you note further on there are two
hashes here merely to ensure that people can test their code.
>In 9.3 Message-Instance lets you do multiple hashes with AND or OR logic with
>hash-any or hash-all. That doesn't make much sense.
up to a point Lord Copper
> PQCs are irrelevant to hash
>functions because hashes are not reversible. The reason we abandoned SHA1 is
>that
>someone found a conventional collision attack. SHA256 and SHA512 are basically
>the same algorithm with different parameters, so it seems likely that if one is
>broken, both are.
>
>I would get rid of the hash-any option and keep hash-all, so the verifier has
>to
>check every hash it understands and pass if all the ones it checked are good.
if we introduce a new hash I'd expect to see signing with
sha256 OR newhash
because a Verifier would not necessarily understand newhash. If we only
keep hash-all such a Verifier would fail the message (the result for
something you do not understand is a fail).
There's not huge complexity from having both AND and OR, and if you want
to test that Verifiers are conformant you would use AND ... so I'd
rather keep both AND and OR
- --
richard @ highwayman . com "Nothing seems the same
Still you never see the change from day to day
And no-one notices the customs slip away"
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