RSA / DSS (keylenghts)

[Mr. B]

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On Thu, Sep 21, 2000 at 05:53:38PM +0100, Pete Chown wrote:
> Ralf Senderek wrote:
>=20
> > if you double the size of a DSS-key not one additional secret key value
> > is added because the amount of possible secret keys is limited by the
> > size of the hash-function (160 bits), Only the mathematical operation=
=20
> > will use a longer key (as modulus) and consequently takes more time.
>=20
> This is true, but hopefully it makes cryptanalysis more difficult.  By
> the time you get to a 1024-bit modulus, it will take roughly the same
> amount of time to solve either of the two possible discrete logarithm
> problems.  With a 512-bit modulus, it is (counterintuitively) much
> easier to attack the 512-bit discrete logarithm problem rather than
> the 160-bit one, because they have different characteristics.  (I am
> sure you already knew that though.)
>=20
> There is no reason why you couldn't have a DSA key longer than 1024
> bits (that I am aware of).  However, to get any benefit from this you
> would need to make the other modulus longer than 160 bits.  This would
> mean using a hash function other than SHA-1, for example Tiger/192.
>=20
> --=20
> Pete
>=20
> --=20
> Archive is at http://lists.gnupg.org - Unsubscribe by sending mail
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>=20
So... what functionality did the gpg RSA upgrade really give us anyway?

Roger Brown
--=20
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