Selection of digest algorithm

David Shaw dshaw at
Thu Jan 29 00:50:34 CET 2009

On Jan 28, 2009, at 6:06 PM, Sven Radde wrote:

> Hi gnupg-users!
> I noticed some "oddities" (to me) with the selection of a hash  
> algorithm
> by GnuPG. I assume that the particular use-cases have additional
> limitations which are not obvious to me, so could you please clarify?
> First, when sending a signed email from Evolution, SHA1 seems to be
> chosen, no matter what "personal-digest-preferences" or even
> "digest-algo" is set in the gpg.conf file (other parts of gpg.conf are
> honored, however).
> Is this a limitation of the PGP/MIME standard that Evolution uses?

No.  OpenPGP/MIME can use any hash that OpenPGP can.  Possibly  
Evolution is overriding the gpg.conf setting for your hashes?

> Second, when using the smartcard, and "personal-digest-preferences
> SHA256 RIPEMD160", the latter is chosen as digest algorithm.
> Is the smartcard limited to 160 Bit hashes?

Yes.  Or at least the current one is.  There is a new version of the  
spec that allows for more hashes, but I don't believe there is a  
physical card based on the updated spec that you can purchase yet.


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