On Sat, May 31, 2008 at 11:08:21AM -0700, [EMAIL PROTECTED] wrote:
On Fri, May 30, 2008 at 05:05:38PM -0700, James G. Sack (jim) wrote:
I guess people got used to describing public key operations in terms of
RSA (keys and methods, I guess). But for reasons I can't remember, I
specify -tdsa when I run ssh-keygen, so I get DSA keys not RSA keys.
The only reason I always say and use RSA is I took the time while back
to understand and implement RSA....which by the way is pretty simple.
DSA uses the same basic group and "hard" as RSA. It has the advantage or
disadvantage (depending on your perspective) that it can only be used for
signatures. Applications that need public key encryption as well typically
pair DSA with something like ElGamal (which is based on the discrete
logarithm problem).
DSA has been granted royalty free use by the patent holder.
A neat consequence of this separation of keys is that now gpg/pgp allow
them to be managed separately. It is common to have a long-lived signing
key, but have an encryption key with a shorter lifetime. Since it is the
signing key that is signed by others and is what is trusted, I can create
new encryption keys whenever I want, and just sign them.
David
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