Two distinct DSA keys sign a file with the same signature. Is this repudiation issue?

[John Newman]

On Tue, Sep 27, 2016 at 06:06:40PM +0300, Georgi Guninski wrote:
> On Tue, Sep 27, 2016 at 02:43:48PM +0000, Sean Lynch wrote:
> > > Is this a bug at all?
> > >
> > 
> > I think the bug is that openssl is silently ignoring parameters, because
> > I'm pretty sure what you're doing is producing and verifying sha1 hashes,
> > not cryptographic signatures. Which means your keys aren't entering the
> > picture at all.
> > I
> >
> 
> No, this is not the case. openssl do the math. I verified both
> signatures in my sage implementation and in python's Crypto.DSA, so math
> is going on, not only hashes.
> 
> This fails in the same directory with a random new key:
> 
> $ openssl dsaparam 1024 > dsapar ; openssl gendsa dsapar > keyrandom.priv ; openssl dsa -in keyrandom.priv -pubout -out keyrandom.pub
> $ openssl dgst -sha1 -verify keyrandom.pub -signature file.txt.sig file.txt
> Verification Failure

Yeah, I emailed too soon...  Thats what I got too.


John 
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