Messages in this thread | | | From | David Howells <> | Subject | Re: [PATCH 4/8] akcipher: Move the RSA DER encoding to the crypto layer | Date | Fri, 26 Feb 2016 11:42:14 +0000 |
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Andrew Zaborowski <balrogg@googlemail.com> wrote:
> Without overhauling akcipher you could modify pkcs1pad so that sign > takes the hash as input, adds the DER struct in front of it to build > the signature, and the verify operation could at most check that the > DER string matches the hash type and return the hash. But I think > RFC2437 suggests that you rather compare the signatures, not the > hashes.
Whilst that is true about what RFC2437 shows, I wonder how strict it wants to be about that rather than it just being a convenient way of describing the algorithm.
The advantage of doing it the way the RFC suggests is that you get to use the EMSA-PKCS1-V1_5-ENCODE operation twice, thereby saving code and only having one place for bugs to occur instead of two - but you can argue this either way.
That said, I would be okay with it returning just the message hash with the padding stripped off, providing the padding is validated in the crypto layer, if that's necessary.
David
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