Re: forward secrecy in mixmaster

[paul@fatmans.demon.co.uk]

> This has been discussed extensively for Internet security reasons, and the
> Photuris folks decided to use a common modulus (actually, several with different
> lengths.)  I think they chose a strong prime (form p = 2q+1, q prime),
> specifically to avoid small-prime attacks, though they may have decided
> that that was no longer necessary.

I assume from the last sentence that you know that the use of strong 
primes is no longer advantageous but I will just reiterate it here 
for the good of those writing code which implements strong primes:

Strong primes are no longer of any benefit for cryptographic 
applications.

The elliptic curve method of factoring takes no longer to factor a 
"strong" prime than it does for any other general number.
You may *SLIGHTLY* hinder progress if an attacker sieves first, but 
as you should have done so when you created the primes in the first 
place it won`t be a problem because there wont be any small factors.

Implementing strong primes won`t make your code any less secure, it 
will just take longer to create the keys and won`t gain you any 
security, all te big boys are using elliptic curve factoring methods 
now so you really have nothing to gain.


  Datacomms Technologies web authoring and data security
     Paul Bradley, Paul@fatmans.demon.co.uk
       Http://www.fatmans.demon.co.uk/crypt/
         "Don`t forget to mount a scratch monkey"

-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: 2.6.3ia
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=CMZA
-----END PGP PUBLIC KEY BLOCK-----