# Re: Diffie-Hellman key exchange

*From*: Bryan <bryanjugglercryptographer@xxxxxxxxx>*Date*: Mon, 10 May 2010 11:35:58 -0700 (PDT)

stevenvh asked:

let the one-way function be (a ^ b) mod m. What are typical ranges for

a, b and m? I guess a can be small ( 10^1 ?) since (a ^ b) becomes

rather large very quickly.

Yes, the base can be small, as long as it generates a large subgroup

of the multiplicative group mod m. RFC 3526 specifies some groups for

Diffie-Hellman key exchange that use 2 as the base.

You can find more guidance on sizes in:

http://csrc.nist.gov/publications/nistpubs/800-57/sp800-57-Part1-revised2_Mar08-2007.pdf

--

--Bryan

.

**References**:**Diffie-Hellman key exchange***From:*stevenvh

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