BN_num_bytes
*var = vmalloc(BN_num_bytes(bn));
binbuf = vmalloc(BN_num_bytes(in));
binlen = BN_num_bytes(bn);
binlen = 1 + BN_num_bytes(RSA_get0_e(key)) + BN_num_bytes(RSA_get0_n(key));
int BN_num_bytes(const BIGNUM */*a*/);
numbits = BN_num_bytes(v) * 8;