BN_mpi2bn
BIGNUM *BN_mpi2bn(const unsigned char *s, int len, BIGNUM *ret);
LCRYPTO_ALIAS(BN_mpi2bn);
LCRYPTO_USED(BN_mpi2bn);
if (BN_mpi2bn(bct->mpi, bct->mpi_len, bn) == NULL) {