secp256k1_ecdh.h (2562B)
1 #ifndef SECP256K1_ECDH_H 2 #define SECP256K1_ECDH_H 3 4 #include "secp256k1.h" 5 6 #ifdef __cplusplus 7 extern "C" { 8 #endif 9 10 /** A pointer to a function that hashes an EC point to obtain an ECDH secret 11 * 12 * Returns: 1 if the point was successfully hashed. 13 * 0 will cause secp256k1_ecdh to fail and return 0. 14 * Other return values are not allowed, and the behaviour of 15 * secp256k1_ecdh is undefined for other return values. 16 * Out: output: pointer to an array to be filled by the function 17 * In: x32: pointer to a 32-byte x coordinate 18 * y32: pointer to a 32-byte y coordinate 19 * data: arbitrary data pointer that is passed through 20 */ 21 typedef int (*secp256k1_ecdh_hash_function)( 22 unsigned char *output, 23 const unsigned char *x32, 24 const unsigned char *y32, 25 void *data 26 ); 27 28 /** An implementation of SHA256 hash function that applies to compressed public key. 29 * Populates the output parameter with 32 bytes. */ 30 SECP256K1_API const secp256k1_ecdh_hash_function secp256k1_ecdh_hash_function_sha256; 31 32 /** A default ECDH hash function (currently equal to secp256k1_ecdh_hash_function_sha256). 33 * Populates the output parameter with 32 bytes. */ 34 SECP256K1_API const secp256k1_ecdh_hash_function secp256k1_ecdh_hash_function_default; 35 36 /** Compute an EC Diffie-Hellman secret in constant time 37 * 38 * Returns: 1: exponentiation was successful 39 * 0: scalar was invalid (zero or overflow) or hashfp returned 0 40 * Args: ctx: pointer to a context object. 41 * Out: output: pointer to an array to be filled by hashfp. 42 * In: pubkey: a pointer to a secp256k1_pubkey containing an initialized public key. 43 * seckey: a 32-byte scalar with which to multiply the point. 44 * hashfp: pointer to a hash function. If NULL, 45 * secp256k1_ecdh_hash_function_sha256 is used 46 * (in which case, 32 bytes will be written to output). 47 * data: arbitrary data pointer that is passed through to hashfp 48 * (can be NULL for secp256k1_ecdh_hash_function_sha256). 49 */ 50 SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdh( 51 const secp256k1_context *ctx, 52 unsigned char *output, 53 const secp256k1_pubkey *pubkey, 54 const unsigned char *seckey, 55 secp256k1_ecdh_hash_function hashfp, 56 void *data 57 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); 58 59 #ifdef __cplusplus 60 } 61 #endif 62 63 #endif /* SECP256K1_ECDH_H */