« Return to Thread: a question about Diffie-Hellman key exchange mode

RE: a question about Diffie-Hellman key exchange mode

by PMHager :: Rate this Message:

Reply to Author | View in Thread

Some parts of this message have been removed. Learn more about Nabble's security policy.

William,

have a look at MODP (Modular Exponential DH Groups) referenced in RFC5246:

RFC2409 defines primes for 768 and 1024 bit, and

RFC3526 defines primes for 1536, 2048, and 3072 bit.

(The generator is always 2.)

Peter-Michael

From: owner-openssl-users@... [mailto:owner-openssl-users@...] On Behalf Of William Cai
Sent: Monday, July 06, 2009 3:25 AM
To: openssl-users@...
Subject: Re: a question about Diffie-Hellman key exchange mode

Thanks Michael! Could you please share me some information about when/how to agree upon p & g?

Thanks,
William

From: Michael Sierchio <kudzu@...>
To: openssl-users@...
Sent: Sunday, July 5, 2009 11:58:42 PM
Subject: Re: a question about Diffie-Hellman key exchange mode

William Cai wrote:

> According to my understanding, Diffie-Hellman algorithm is based on
> something like this,
> 1. public prime number, p
> 2. public base, g
> 3. Side A's private key, a
> 4. Side A's public key, A = g ^ a mod p
> 5. Side B's private key, b
> 6. Side B's public key, B = g ^ b mod p
>
> The question is that which items above the Diffie-Hellman public
> parameters consist of? If they are 1, 2 and 4, then we need at least an
> additional step pass the public prime number and public base to the
> other side, otherwise, the other side cannot calculate its public key.
> right? But I don't see such description in the paper. Are public prime
> number and public base presetted?

Yes, the p and g are well known and agreed upon in advance.

______________________________________________________________________
OpenSSL Project http://www.openssl.org
User Support Mailing List openssl-users@...
Automated List Manager majordomo@...

« Return to Thread: a question about Diffie-Hellman key exchange mode