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Re: cvs: Permission denied (publickey).

On Sat August 23 2008, Jeffrey Ollie wrote:
> 2008/8/23 Axel Thimm <Axel Thimm atrpms net>:

> > Have DSA keys now been banned?
> Yes.
> > Why?
> The primary reason is that it's nearly impossible to tell if the key
> was generated on a Debian system with the compromised OpenSSL

This is also true for RSA keys.

> versions.  I've heard rumblings that DSA keys are weaker for other
> reasons, but I've not seen any good explanations.

| In addition, any DSA key must be considered compromised if it has been used
| on a machine with a 'bad' OpenSSL. Simply using a 'strong' DSA key (i.e.,
| generated with a 'good' OpenSSL) to make a connection from such a machine
| may have compromised it. This is due to an 'attack' on DSA that allows the
| secret key to be found if the nonce used in the signature is known or
| reused.     

If you look at the descriptions of the dsa signing algorithm, e.g. in the 
handbook of applied cryptography[1], you notice, that there is a random 
parameter that is meant to kept secret.


[1] http://www.cacr.math.uwaterloo.ca/hac/about/chap11.pdf

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