1: exponentiation was successful 0: scalar was invalid (zero or overflow) or hashfp returned 0 Args: ctx: pointer to a context object. Out: output: pointer to an array to be filled by hashfp. In: pubkey: a pointer to a secp256k1_pubkey containing an initialized public key. seckey: a 32-byte scalar with which to multiply the point. hashfp: pointer to a hash function. If NULL, secp256k1_ecdh_hash_function_sha256 is used (in which case, 32 bytes will be written to output). data: arbitrary data pointer that is passed through to hashfp (can be NULL for secp256k1_ecdh_hash_function_sha256).
Compute an EC Diffie-Hellman secret in constant time