Re: Diffie-Hellman 128 bit

[Hagai Bar-El]

At 13/03/03 23:48, you wrote:
I am looking at attacks on Diffie-Hellman.

The protocol implementation I'm looking at designed their diffie-hellman
using 128 bit primes (generated each time, yet P-1/2 will be a prime, so no
go on pohlig-hellman attack), so what attacks are there that I can look at
to come up with either the logarithm x from (a=g^x mod p) or the session key
that is
calculated. A brute force wouldn't work, unless I know the starting range.
Are there any realistic
attacks on DH parameters of this size, or is theoretically based on
financial computation attacks?


You can find good explanation for the rationale behind Diffie-Hellman 
parameters as well as general precautions for implementation in a good 
paper called "Security Issues in the Diffie-Hellman Key Agreement Protocol"

You can find it in: http://citeseer.nj.nec.com/483430.html

Regards,
Hagai.


Hagai Bar-El - Information Security Analyst
Tel.: 972-8-9354152  Fax.: 972-8-9354152
E-mail: [EMAIL PROTECTED]  Web: www.hbarel.com


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