github.com/klaytn/klaytn@v1.12.1/crypto/secp256k1/libsecp256k1/src/ecmult_gen.h (about)

     1  /**********************************************************************
     2   * Copyright (c) 2013, 2014 Pieter Wuille                             *
     3   * Distributed under the MIT software license, see the accompanying   *
     4   * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
     5   **********************************************************************/
     6  
     7  #ifndef _SECP256K1_ECMULT_GEN_
     8  #define _SECP256K1_ECMULT_GEN_
     9  
    10  #include "scalar.h"
    11  #include "group.h"
    12  
    13  typedef struct {
    14      /* For accelerating the computation of a*G:
    15       * To harden against timing attacks, use the following mechanism:
    16       * * Break up the multiplicand into groups of 4 bits, called n_0, n_1, n_2, ..., n_63.
    17       * * Compute sum(n_i * 16^i * G + U_i, i=0..63), where:
    18       *   * U_i = U * 2^i (for i=0..62)
    19       *   * U_i = U * (1-2^63) (for i=63)
    20       *   where U is a point with no known corresponding scalar. Note that sum(U_i, i=0..63) = 0.
    21       * For each i, and each of the 16 possible values of n_i, (n_i * 16^i * G + U_i) is
    22       * precomputed (call it prec(i, n_i)). The formula now becomes sum(prec(i, n_i), i=0..63).
    23       * None of the resulting prec group elements have a known scalar, and neither do any of
    24       * the intermediate sums while computing a*G.
    25       */
    26      secp256k1_ge_storage (*prec)[64][16]; /* prec[j][i] = 16^j * i * G + U_i */
    27      secp256k1_scalar blind;
    28      secp256k1_gej initial;
    29  } secp256k1_ecmult_gen_context;
    30  
    31  static void secp256k1_ecmult_gen_context_init(secp256k1_ecmult_gen_context* ctx);
    32  static void secp256k1_ecmult_gen_context_build(secp256k1_ecmult_gen_context* ctx, const secp256k1_callback* cb);
    33  static void secp256k1_ecmult_gen_context_clone(secp256k1_ecmult_gen_context *dst,
    34                                                 const secp256k1_ecmult_gen_context* src, const secp256k1_callback* cb);
    35  static void secp256k1_ecmult_gen_context_clear(secp256k1_ecmult_gen_context* ctx);
    36  static int secp256k1_ecmult_gen_context_is_built(const secp256k1_ecmult_gen_context* ctx);
    37  
    38  /** Multiply with the generator: R = a*G */
    39  static void secp256k1_ecmult_gen(const secp256k1_ecmult_gen_context* ctx, secp256k1_gej *r, const secp256k1_scalar *a);
    40  
    41  static void secp256k1_ecmult_gen_blind(secp256k1_ecmult_gen_context *ctx, const unsigned char *seed32);
    42  
    43  #endif