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-rw-r--r--src/secp256k1/include/secp256k1_ecdh.h37
1 files changed, 22 insertions, 15 deletions
diff --git a/src/secp256k1/include/secp256k1_ecdh.h b/src/secp256k1/include/secp256k1_ecdh.h
index df5fde235c..4058e9c043 100644
--- a/src/secp256k1/include/secp256k1_ecdh.h
+++ b/src/secp256k1/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);