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Re: ElGamal, EME-PKCS1-v1_5

2010-06-24 15:27:37

On Thursday, 24.06.10 at 22:52, Marko Kreen wrote:
On 6/24/10, Brian Lewis <brian(_at_)monetra(_dot_)com> wrote:
 I'm trying to generate a tag 1 (public-key encrypted session key)
 packet.

 I'm using ElGamal, so the algorithm-specific fields are, according to
 http://tools.ietf.org/html/rfc4880#section-5.1,
 MPI g**k mod p
 MPI m * y**k mod p

 So I need m = EME-PKCS1-v1_5(...). According to
 http://tools.ietf.org/html/rfc3447#section-7.2.1, PS is k - mLen
 - 3 random nonzero bytes, where k is the length of RSA n in bytes. But I
 don't have RSA n. I have ElGamal p, g, and y.

 In EME-PKCS1-v1_5, what is k if I'm using ElGamal?

mod p ~ mod n

I don't understand. Could you elaborate?

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