Re: keys longer than 1024 bits

On Wed, Sep 13, 2006 at 02:09:38PM +0000, edbch wrote:
> Hello to all.
> First they pardon my bad English.
> I am attempted to generate keys longer than 1024 bits, but I am not 
> obtaining. I perceived that in some machines this is possible and in others 
> not.
> It is some problem because of the operational system and some rule or 
> because of the version of ssh? In the machines that I cannot generate these 
> keys I use Gentoo Linux and OpenSSH_4.3p2, OpenSSL 0.9.7j. In that I can I 
> use OpenBSD and OpenSSH_4.1, OpenSSL 0.9.7d. The command to generate the 
> keys that I used is: ssh-keygen - t dsa - b the 2048 and message of error 
> that I received is:  DSA keys must be 1024 bits.
> Somebody knows to explain me because?  Debtor since now.
>
> Eduardo

The ssh-keygen manpage says:

     -b bits
             Specifies the number of bits in the key to create.  For RSA
             keys, the minimum size is 768 bits and the default is 2048
bits.
             Generally, 2048 bits is considered sufficient.  DSA keys
must be
             exactly 1024 bits as specified by FIPS 186-2.

DSA keys must be exactly 1024 bits, according to the standard.  If you
want larger keys, you'll need to make RSA keys instead of DSA keys.


-Ian

-- 
Ian Becker
ibecker@post.harvard.edu