ecc_sign_common
static int ecc_sign_common(ecc_ctx_t *, crypto_data_t *, crypto_data_t *,
rv = ecc_sign_common((ecc_ctx_t *)ctxp, &der_cd, signature,
rv = ecc_sign_common(ctxp, data, signature, req);
rv = ecc_sign_common(&ctx, data, signature, req);