Re: ElGamal, EME-PKCS1-v1_5

[Marko Kreen <markokr@xxxxxxxxx>]

On 6/24/10, Brian Lewis <brian@xxxxxxxxxxx> 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

-- 
marko