How do I create a M2Crypto DSA object given parameters and key values?

Question

Using M2Crypto I'd like to create a DSA_pub object for verifying a DSA signature. I know q, p, g, and the public key, but the only way I know to instantiate a DSA object is using:

dsa = DSA.set_params(q,p,g)
dsa.gen_key()

How do I assign the known public key?

Answer 1

There are many factory functions in module DSA beyond get_params, and I think you want load_pub_key (if you have public key and params in a PEM file) or load_pub (if you have them in a BIO object). See also the BIO module for various kinds of BIO objects.