diff options
Diffstat (limited to 'include/secp256k1_ecdh.h')
| -rw-r--r-- | include/secp256k1_ecdh.h | 37 |
1 files changed, 22 insertions, 15 deletions
diff --git a/include/secp256k1_ecdh.h b/include/secp256k1_ecdh.h index df5fde235c..4058e9c043 100644 --- a/include/secp256k1_ecdh.h +++ b/include/secp256k1_ecdh.h @@ -7,43 +7,50 @@ extern "C" { #endif -/** A pointer to a function that applies hash function to a point +/** A pointer to a function that hashes an EC point to obtain an ECDH secret * - * Returns: 1 if a point was successfully hashed. 0 will cause ecdh to fail - * Out: output: pointer to an array to be filled by the function - * In: x: pointer to a 32-byte x coordinate - * y: pointer to a 32-byte y coordinate - * data: Arbitrary data pointer that is passed through + * 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 */ typedef int (*secp256k1_ecdh_hash_function)( unsigned char *output, - const unsigned char *x, - const unsigned char *y, + const unsigned char *x32, + const unsigned char *y32, void *data ); -/** An implementation of SHA256 hash function that applies to compressed public key. */ +/** An implementation of SHA256 hash function that applies to compressed public key. + * Populates the output parameter with 32 bytes. */ SECP256K1_API extern const secp256k1_ecdh_hash_function secp256k1_ecdh_hash_function_sha256; -/** A default ecdh hash function (currently equal to 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. */ SECP256K1_API extern 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) + * 0: scalar was invalid (zero or overflow) or hashfp returned 0 * Args: ctx: pointer to a context object (cannot be NULL) - * Out: output: pointer to an array to be filled by the function + * Out: output: pointer to an array to be filled by hashfp * In: pubkey: a pointer to a secp256k1_pubkey containing an * initialized public key - * privkey: a 32-byte scalar with which to multiply the point + * 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 - * data: Arbitrary data pointer that is passed through + * (in which case, 32 bytes will be written to output) + * data: arbitrary data pointer that is passed through to hashfp */ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdh( const secp256k1_context* ctx, unsigned char *output, const secp256k1_pubkey *pubkey, - const unsigned char *privkey, + const unsigned char *seckey, secp256k1_ecdh_hash_function hashfp, void *data ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); |