github.com/ethereum/go-ethereum@v1.16.1/crypto/secp256k1/libsecp256k1/include/secp256k1_ecdh.h (about)

     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:     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 */