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: info at hbarel.com  Web: www.hbarel.com



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