Wrong signature hash detection?

[David Shaw]

On May 6, 2010, at 11:47 PM, Hauke Laging wrote:

> Am Freitag 07 Mai 2010 05:15:10 schrieb Daniel Kahn Gillmor:
> 
>> Are you judging based on the size of the block?
> 
> Yes. :-)
> 
> 
>> RSA signatures are
>> significantly larger than DSA signatures, even though they sign over the
>> same digest algorithm.
> 
> OK. Thanks. So RSA signatures have the same size for different digest 
> algorithms?

The RSA signature size is based on the size of the RSA key (a bigger key means a bigger signature).  DSA signature sizes are based on the size of a value called "q", used when generating the key.  Usually, this is loosely tied to the hash and also the key size, but it doesn't have to be.

David