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?
Thank you.