module include.secp256k1_ecdh;

import include.secp256k1;

extern (C):

/** A pointer to a function that hashes an EC point to obtain an ECDH secret
 *
 *  Returns: 1 if the point was successfully hashed.
 *           0 will cause secp256k1_ecdh to fail and return 0.
 *           Other return values are not allowed, and the behaviour of
 *           secp256k1_ecdh is undefined for other return values.
 *  Out:     output:     pointer to an array to be filled by the function
 *  In:      x32:        pointer to a 32-byte x coordinate
 *           y32:        pointer to a 32-byte y coordinate
 *           data:       arbitrary data pointer that is passed through
 */
alias secp256k1_ecdh_hash_function = int function(ubyte* output,
        const(ubyte)* x32, const(ubyte)* y32, void* data);

/** An implementation of SHA256 hash function that applies to compressed public key.
 * Populates the output parameter with 32 bytes. */
extern __gshared const secp256k1_ecdh_hash_function secp256k1_ecdh_hash_function_sha256;

/** A default ECDH hash function (currently equal to secp256k1_ecdh_hash_function_sha256).
 * Populates the output parameter with 32 bytes. */
extern __gshared const secp256k1_ecdh_hash_function secp256k1_ecdh_hash_function_default;

/** Compute an EC Diffie-Hellman secret in constant time
 *
 *  Returns: 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).
 */
int secp256k1_ecdh(const(secp256k1_context)* ctx, ubyte* output, const(secp256k1_pubkey)* pubkey,
        const(ubyte)* seckey, secp256k1_ecdh_hash_function hashfp, void* data);

/* SECP256K1_ECDH_H */