Re: 128bit RSA public key - time to break?

From: Tom St Denis (tomstdenis@iahu.ca)
Date: 02/23/03 

From: "Tom St Denis" <tomstdenis@iahu.ca>
Date: Sat, 22 Feb 2003 20:36:53 -0500

"shane" <shanehird@hotmail.com> wrote in message
news:bb693fad.0302221727.274f070e@posting.google.com...
> I realise that a 128bit key would be exceptionally weak, but I haven't
> been able to find out just how weak it is.
>
> I am in need of a small public key, which would provide security from
> a typical user for about 6 months. Security in this situation isn't
> paramount, 6 months would be plenty enough to deter anyone from
> bothering to try - more important is the size of the key - it would be
> great if it could be 128 bits or less.

6 Months you'd probably need at least ~650 bits or so is my guess [though I
wouldn't venture below 1024 bits].

> Can anyone recommend a key size?
> Or an algorithm? I considered ECC, but it seems to have a minimum of
> 160bits. Is this the case?

Unless you use ONB [e.g. curves over patented mathematical fields... shame!]
ECC is in fact slower than RSA for most processors. Though a ECC-192 op
over GF(p) is fairly fast [~24ms iirc] on say a Athlon XP.

Tom