ec_pubkey_fast.c

/* Copyright (c) 2015 Nicolas Courtois, Guangyan Song, Ryan Castellucci, All Rights Reserved */
#include "ec_pubkey_fast.h"

#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>

#include "secp256k1/src/libsecp256k1-config.h"
#include "secp256k1/include/secp256k1.h"

#include "secp256k1/src/util.h"
#include "secp256k1/src/num_impl.h"
#include "secp256k1/src/field_impl.h"
#include "secp256k1/src/field_10x26_impl.h"
#include "secp256k1/src/scalar_impl.h"
#include "secp256k1/src/group_impl.h"
#include "secp256k1/src/ecmult_gen_impl.h"
#include "secp256k1/src/ecmult.h"

#include "mmapf.h"

#undef ASSERT

#define READBIT(A, B) ((A >> (B & 7)) & 1)
#define SETBIT(T, B, V) (T = V ? T | (1<<B) : T & ~(1<<B))
int n_windows = 0;
int n_values;
secp256k1_gej_t nums_gej;
secp256k1_ge_t *prec;
int remmining = 0;
int WINDOW_SIZE = 0;
size_t MMAP_SIZE;
mmapf_ctx prec_mmapf;

int secp256k1_ec_pubkey_precomp_table_save(int window_size, unsigned char *filename) {
  int fd, ret;
  size_t records;
  FILE *dest;

  if ((ret = secp256k1_ec_pubkey_precomp_table(window_size, NULL)) < 0)
    return ret;

  if ((fd = open(filename, O_RDWR | O_CREAT | O_EXCL, 0660)) < 0)
    return fd;

  records = n_windows*n_values;
  dest = fdopen(fd, "w");
  if (fwrite(prec, sizeof(secp256k1_ge_t), n_windows*n_values, dest) != records)
    return -1;

  return 0;
}

int secp256k1_ec_pubkey_precomp_table(int window_size, unsigned char *filename) {
  int ret;
  struct stat sb;
  size_t prec_sz;
  secp256k1_gej_t gj; // base point in jacobian coordinates
  secp256k1_gej_t *table;

  if (filename) {
    if (stat(filename, &sb) == 0) {
      if (!S_ISREG(sb.st_mode))
        return -100;
    } else {
      return -101;
    }
  }

  // try to find a window size that matched the file size
  for (;;) {
    WINDOW_SIZE = window_size;
    n_values = 1 << window_size;
    if (256 % window_size == 0) {
      n_windows = (256 / window_size);
    } else {
      n_windows = (256 / window_size) + 1;
    }
    remmining = 256 % window_size;
    prec_sz = n_windows*n_values*sizeof(secp256k1_ge_t);
    if (!filename || sb.st_size <= prec_sz)
      break;
    ++window_size;
  }

  if ((ret = mmapf(&prec_mmapf, filename, prec_sz, MMAPF_RNDRD)) != MMAPF_OKAY) {
    fprintf(stderr, "failed to open ecmult table '%s': %s\n", filename, mmapf_strerror(ret));
    exit(1);
  } else if (prec_mmapf.mem == NULL) {
    fprintf(stderr, "got NULL pointer from mmapf\n");
    exit(1);
  }
  prec = prec_mmapf.mem;

  if (filename) { return 0; }

  table = malloc(n_windows*n_values*sizeof(secp256k1_gej_t));

  secp256k1_gej_set_ge(&gj, &secp256k1_ge_const_g);

  //fprintf(stderr, "%d %d %d %d %zu\n", window_size, n_windows, n_values, remmining, prec_sz);

  static const unsigned char nums_b32[33] = "The scalar for this x is unknown";
  secp256k1_fe_t nums_x;
  secp256k1_ge_t nums_ge;
  VERIFY_CHECK(secp256k1_fe_set_b32(&nums_x, nums_b32));
  VERIFY_CHECK(secp256k1_ge_set_xo_var(&nums_ge, &nums_x, 0));
  secp256k1_gej_set_ge(&nums_gej, &nums_ge);
  /* Add G to make the bits in x uniformly distributed. */
  secp256k1_gej_add_ge_var(&nums_gej, &nums_gej, &secp256k1_ge_const_g, NULL);

  secp256k1_gej_t gbase;
  secp256k1_gej_t numsbase;
  gbase = gj; /* (2^w_size)^num_of_windows * G */
  numsbase = nums_gej; /* 2^num_of_windows * nums. */

  for (int j = 0; j < n_windows; j++) {
    //[number of windows][each value from 0 - (2^window_size - 1)]
    table[j*n_values] = numsbase;
    for (int i = 1; i < n_values; i++) {
      secp256k1_gej_add_var(&table[j*n_values + i], &table[j*n_values + i - 1], &gbase, NULL);
    }

    for (int i = 0; i < window_size; i++) {
      secp256k1_gej_double_var(&gbase, &gbase, NULL);
    }
    /* Multiply numbase by 2. */
    secp256k1_gej_double_var(&numsbase, &numsbase, NULL);
    if (j == n_windows-2) {
      /* In the last iteration, numsbase is (1 - 2^j) * nums instead. */
      secp256k1_gej_neg(&numsbase, &numsbase);
      secp256k1_gej_add_var(&numsbase, &numsbase, &nums_gej, NULL);
    }
  }
  secp256k1_ge_set_all_gej_var(n_windows*n_values, prec, table, 0);

  free(table);
  return 0;
}

static void secp256k1_ecmult_gen2(secp256k1_gej_t *r, const unsigned char *seckey){
  unsigned char a[256];
  for (int j = 0; j < 32; j++) {
    for (int i = 0; i < 8; i++) {
      a[i+j*8] = READBIT(seckey[31-j], i);
    }
  }

  r->infinity = 1;
  int bits;

  for (int j = 0; j < n_windows; j++) {
    if (j == n_windows -1 && remmining != 0) {
      bits = 0;
      for (int i = 0; i < remmining; i++) {
        SETBIT(bits,i,a[i + j * WINDOW_SIZE]);
      }
    } else {
      bits = 0;
      for (int i = 0; i < WINDOW_SIZE; i++) {
        SETBIT(bits,i,a[i + j * WINDOW_SIZE]);
      }
    }
#if 1
    secp256k1_gej_add_ge_var(r, r, &prec[j*n_values + bits], NULL);
#else
    secp256k1_gej_add_ge(r, r, &prec[j*n_values + bits]);
#endif
  }
}

#ifdef USE_BL_ARITHMETIC
static void secp256k1_gej_add_ge_bl(secp256k1_gej_t *r, const secp256k1_gej_t *a, const secp256k1_ge_t *b, secp256k1_fe_t *rzr) {
  secp256k1_fe_t z1z1, /*z1,*/ u2, x1, y1, t0, s2, h, hh, i, j, t1, rr,  v, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11;
  // 7M + 4S + 2 normalize + 22 mul_int/add/negate
  if (a->infinity) {
    VERIFY_CHECK(rzr == NULL);
    secp256k1_gej_set_ge(r, b);
    return;
  }
  if (b->infinity) {
    if (rzr) {
      secp256k1_fe_set_int(rzr, 1);
    }
    *r = *a;
    return;
  }
  r->infinity = 0;

  x1 = a->x; secp256k1_fe_normalize_weak(&x1);
  y1 = a->y; secp256k1_fe_normalize_weak(&y1);

  secp256k1_fe_sqr(&z1z1, &a->z);                                     // z1z1 = z1^2
  secp256k1_fe_mul(&u2, &b->x, &z1z1);                                // u2 = x2*z1z1
  secp256k1_fe_mul(&t0, &a->z, &z1z1);                                // t0 = z1*z1z1
  secp256k1_fe_mul(&s2, &b->y, &t0);                                  // s2 = y2 * t0
  secp256k1_fe_negate(&h, &x1, 1); secp256k1_fe_add(&h, &u2);         // h = u2-x1  (3)
  secp256k1_fe_sqr(&hh,&h);                                           // hh = h^2
  i = hh; secp256k1_fe_mul_int(&i,4);                                 // i = 4*hh
  if (secp256k1_fe_normalizes_to_zero_var(&h)) {
    if (secp256k1_fe_normalizes_to_zero_var(&i)) {
      secp256k1_gej_double_var(r, a, rzr);
    } else {
      if (rzr) {
        secp256k1_fe_set_int(rzr, 0);
      }
      r->infinity = 1;
    }
    return;
  }
  secp256k1_fe_mul(&j,&h,&i);                                         // j = h*i
  secp256k1_fe_negate(&t1, &y1, 1); secp256k1_fe_add(&t1, &s2);       // t1 = s2-y1
  rr = t1; secp256k1_fe_mul_int(&rr, 2);                              // rr = 2 * t1;
  secp256k1_fe_mul(&v, &x1, &i);                                      // v = x1 * i
  secp256k1_fe_sqr(&t2, &rr);                                         // t2 = rr^2
  t3 = v; secp256k1_fe_mul_int(&t3, 2);                               // t3 = 2*v
  secp256k1_fe_negate(&t4, &j, 1);   secp256k1_fe_add(&t4, &t2);      // t4 = t2 - j
  secp256k1_fe_negate(&r->x, &t3, 2); secp256k1_fe_add(&r->x, &t4);   // x3 = t4 - t3;
  //secp256k1_fe_normalize_weak(&r->x);
  secp256k1_fe_negate(&t5, &r->x, 6); secp256k1_fe_add(&t5, &v);      // t5 = v - x3
  secp256k1_fe_mul(&t6,&y1,&j);                                       // t6 = y1 * j
  t7 = t6; secp256k1_fe_mul_int(&t7,2);                               // t7 = 2*t6;
  secp256k1_fe_mul(&t8,&rr,&t5);                                      // t8 = rr* t5;
  secp256k1_fe_negate(&r->y, &t7, 2); secp256k1_fe_add(&r->y,&t8);    // y3 = t8-t7
  //secp256k1_fe_normalize_weak(&r->y);
  t9 = h; secp256k1_fe_add(&t9, &a->z);                               // t9 = z1 + h
  secp256k1_fe_sqr(&t10, &t9);                                        // t10 = t9^2
  secp256k1_fe_negate(&t11, &z1z1, 1); secp256k1_fe_add(&t11, &t10);  // t11 = t10-z1z1
  secp256k1_fe_negate(&r->z, &hh, 1); secp256k1_fe_add(&r->z, &t11);  // z3 = t11 - hh

}

static void secp256k1_ecmult_gen_bl(secp256k1_gej_t *r, const unsigned char *seckey){
  unsigned char a[256];
  for (int j = 0; j < 32; j++){
    for (int i = 0; i < 8; i++){
      a[i+j*8] = READBIT(seckey[31-j], i);
    }
  }

  r->infinity = 1;
  int bits;

  for (int j = 0; j < n_windows; j++) {
    if (j == n_windows -1 && remmining != 0) {
      bits = 0;
      for (int i = 0; i < remmining; i++) {
        SETBIT(bits,i,a[i + j * WINDOW_SIZE]);
      }
      //bits = secp256k1_scalar_get_bits2(a, j * WINDOW_SIZE, remmining);
    } else {
      bits = 0;
      for (int i = 0; i < WINDOW_SIZE; i++) {
        SETBIT(bits,i,a[i + j * WINDOW_SIZE]);
      }
      //bits = secp256k1_scalar_get_bits2(a, j * WINDOW_SIZE, WINDOW_SIZE);
    }
    secp256k1_gej_add_ge_bl(r, r, &prec[j*n_values + bits], NULL);
  }
}
#endif

int secp256k1_ec_pubkey_create_precomp(unsigned char *pub_chr, int *pub_chr_sz, const unsigned char *seckey) {
  secp256k1_gej_t pj;
  secp256k1_ge_t p;

#ifdef USE_BL_ARITHMETIC
  secp256k1_ecmult_gen_bl(&pj, seckey);
#else
  secp256k1_ecmult_gen2(&pj, seckey);
#endif
  secp256k1_ge_set_gej(&p, &pj);

  *pub_chr_sz = 65;
  pub_chr[0] = 4;

  secp256k1_fe_normalize_var(&p.x);
  secp256k1_fe_normalize_var(&p.y);
  secp256k1_fe_get_b32(pub_chr +  1, &p.x);
  secp256k1_fe_get_b32(pub_chr + 33, &p.y);

  return 0;
}

inline static void _priv_add(unsigned char *priv, unsigned char add, int p) {
  priv[p] += add;
  if (priv[p] < add) {
    priv[--p] += 1;
    while (p) {
      if (priv[p] == 0) {
        priv[--p] += 1;
      } else {
        break;
      }
    }
  }
}

void priv_add_uint8(unsigned char *priv, unsigned char add) {
  _priv_add(priv, add, 31);
}

void priv_add_uint32(unsigned char *priv, unsigned int add) {
  int p = 31;
  while (add) {
    _priv_add(priv, add & 255, p--);
    add >>= 8;
  }
}

typedef struct {
  secp256k1_gej_t pubj;
  secp256k1_ge_t  inc;
  secp256k1_gej_t incj;
  unsigned int n;
} pubkey_incr_t;

pubkey_incr_t pubkey_incr_ctx;

int secp256k1_ec_pubkey_incr_init(unsigned char *seckey, unsigned int add) {
  unsigned char incr_priv[32];
  memset(incr_priv, 0, sizeof(incr_priv));
  memset(&pubkey_incr_ctx, 0, sizeof(pubkey_incr_ctx));
  priv_add_uint32(incr_priv, add);

  pubkey_incr_ctx.n = add;

#ifdef USE_BL_ARITHMETIC
  secp256k1_ecmult_gen_bl(&pubkey_incr_ctx.pubj, seckey);
  secp256k1_ecmult_gen_bl(&pubkey_incr_ctx.incj, incr_priv);
#else
  secp256k1_ecmult_gen2(&pubkey_incr_ctx.pubj, seckey);
  secp256k1_ecmult_gen2(&pubkey_incr_ctx.incj, incr_priv);
#endif
  secp256k1_ge_set_gej(&pubkey_incr_ctx.inc, &pubkey_incr_ctx.incj);

  return 0;
}

int secp256k1_ec_pubkey_incr(unsigned char *pub_chr, int *pub_chr_sz, unsigned char *seckey) {
  secp256k1_ge_t p;

  priv_add_uint32(seckey, pubkey_incr_ctx.n);
#ifdef USE_BL_ARITHMETIC
  secp256k1_gej_add_ge_bl(&pubkey_incr_ctx.pubj, &pubkey_incr_ctx.pubj, &pubkey_incr_ctx.inc, NULL);
#else
  secp256k1_gej_add_ge_var(&pubkey_incr_ctx.pubj, &pubkey_incr_ctx.pubj, &pubkey_incr_ctx.inc, NULL);
#endif

  secp256k1_ge_set_gej(&p, &pubkey_incr_ctx.pubj);

  *pub_chr_sz = 65;
  pub_chr[0] = 4;

  secp256k1_fe_normalize_var(&p.x);
  secp256k1_fe_normalize_var(&p.y);
  secp256k1_fe_get_b32(pub_chr +  1, &p.x);
  secp256k1_fe_get_b32(pub_chr + 33, &p.y);

  return 0;
}
/*  vim: set ts=2 sw=2 et ai si: */