EVP_PKEY_CTX_set_tls1_prf_md
int EVP_PKEY_CTX_set_tls1_prf_md(EVP_PKEY_CTX *ctx, const EVP_MD *md);
EVP_PKEY_CTX_set_tls1_prf_md(pctx, EVP_md5_sha1());
if (EVP_PKEY_CTX_set_tls1_prf_md(pctx, EVP_sha256()) <= 0) {