[gnupg-users] Preferred hash algorithm when signing

[Robert J. Hansen]

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On 8/21/12 12:26 PM, Laurent Jumet wrote:
> It primary depends on the lenghth of the main (signing) key. If
> main key is 1024, he cannot sign with SHA256; he can sign with a 
> RIPEMD160 but not higher, and other preferences are ignored.

Yes and no.

DSA-1024 requires the use of a 160-bit hash.  If the --enable-dsa2
flag is set, he will be able to sign with any hash he likes: it will
just be silently truncated to 160 bits.  Otherwise, yes, the choices
are SHA-1 and RIPEMD-160.

DSA-2048 requires the use of at least a 224-bit hash.

DSA-3072 requires the use of at least a 256-bit hash.

RSA has no requirements on hash length.
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