How do I feed OpenSSL random data for use in ECDSA signing?

Question

I want to feed OpenSSL specific data for use as random seed during the signing of data with an EC key. I\'m doing this to compare my application with another reference one (

Answer 1

You can control the random data that OpenSSL produces during signing by using the method:

ECDSA_SIG* ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen, const BIGNUM *kinv, const BIGNUM *rp, EC_KEY *eckey);

where kinv is the random number that is used during signing.