Multiple encryption subkeys

[Adrian 'Dagurashibanipal' von Bidder]

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On Wednesday 30 April 2003 01:24, Johan Wevers wrote:
> Adrian 'Dagurashibanipal' von Bidder wrote:
> >I guess the idea is not bad. However, you'd have to match the strength of
> >the public key encryption to the strength of the underlying block cipher=
 -
> > I don't have data on this, but I when you use a 128bit block cipher with
> > a 2048 public key, the block cipher is much easier to break, so with
> > going to 4096bit public key you don't gain anything.
>
> Not really. You need to know that symmetric-key ciphers are usually much
> stronger than public-key ciphers with the same keylength.=20

Yes, that's clear (it's even obvious, to me).

> A 128 bit RSA
> or DH key can be brute-forced easily. Elliptic curves seem to do better
> with short keylengths but they are at this moment much less studied than
> RSA or DH.
>
> 128 bit symmetric is roughly comparable to a 2048 bit RSA or DH key.

I just wasn't sure where this point of (rough) comparability is. But still:=
 if=20
128 bit is comparable to a 2048 RSA key, you don't gain much going to a 409=
6=20
bit RSA key.

cheers
=2D- vbi


=2D-=20
featured link: http://fortytwo.ch/gpg/subkeys

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