Precompute parts of the signing operation
\param eckey EC_KEY object containing a private EC key
\param ctx BN_CTX object (optional)
\param kinv BIGNUM pointer for the inverse of k
\param rp BIGNUM pointer for x coordinate of k* generator
\return 1 on success and 0 otherwise
Precompute parts of the signing operation \param eckey EC_KEY object containing a private EC key \param ctx BN_CTX object (optional) \param kinv BIGNUM pointer for the inverse of k \param rp BIGNUM pointer for x coordinate of k* generator \return 1 on success and 0 otherwise