ecmult_gen_compute_table_impl.h (3528B)
1 /*********************************************************************** 2 * Copyright (c) 2013, 2014, 2015 Pieter Wuille, Gregory Maxwell * 3 * Distributed under the MIT software license, see the accompanying * 4 * file COPYING or https://www.opensource.org/licenses/mit-license.php.* 5 ***********************************************************************/ 6 7 #ifndef SECP256K1_ECMULT_GEN_COMPUTE_TABLE_IMPL_H 8 #define SECP256K1_ECMULT_GEN_COMPUTE_TABLE_IMPL_H 9 10 #include "ecmult_gen_compute_table.h" 11 #include "group_impl.h" 12 #include "field_impl.h" 13 #include "ecmult_gen.h" 14 #include "util.h" 15 16 static void haskellsecp256k1_v0_1_0_ecmult_gen_compute_table(haskellsecp256k1_v0_1_0_ge_storage* table, const haskellsecp256k1_v0_1_0_ge* gen, int bits) { 17 int g = ECMULT_GEN_PREC_G(bits); 18 int n = ECMULT_GEN_PREC_N(bits); 19 20 haskellsecp256k1_v0_1_0_ge* prec = checked_malloc(&default_error_callback, n * g * sizeof(*prec)); 21 haskellsecp256k1_v0_1_0_gej gj; 22 haskellsecp256k1_v0_1_0_gej nums_gej; 23 int i, j; 24 25 VERIFY_CHECK(g > 0); 26 VERIFY_CHECK(n > 0); 27 28 /* get the generator */ 29 haskellsecp256k1_v0_1_0_gej_set_ge(&gj, gen); 30 31 /* Construct a group element with no known corresponding scalar (nothing up my sleeve). */ 32 { 33 static const unsigned char nums_b32[33] = "The scalar for this x is unknown"; 34 haskellsecp256k1_v0_1_0_fe nums_x; 35 haskellsecp256k1_v0_1_0_ge nums_ge; 36 int r; 37 r = haskellsecp256k1_v0_1_0_fe_set_b32_limit(&nums_x, nums_b32); 38 (void)r; 39 VERIFY_CHECK(r); 40 r = haskellsecp256k1_v0_1_0_ge_set_xo_var(&nums_ge, &nums_x, 0); 41 (void)r; 42 VERIFY_CHECK(r); 43 haskellsecp256k1_v0_1_0_gej_set_ge(&nums_gej, &nums_ge); 44 /* Add G to make the bits in x uniformly distributed. */ 45 haskellsecp256k1_v0_1_0_gej_add_ge_var(&nums_gej, &nums_gej, gen, NULL); 46 } 47 48 /* compute prec. */ 49 { 50 haskellsecp256k1_v0_1_0_gej gbase; 51 haskellsecp256k1_v0_1_0_gej numsbase; 52 haskellsecp256k1_v0_1_0_gej* precj = checked_malloc(&default_error_callback, n * g * sizeof(*precj)); /* Jacobian versions of prec. */ 53 gbase = gj; /* PREC_G^j * G */ 54 numsbase = nums_gej; /* 2^j * nums. */ 55 for (j = 0; j < n; j++) { 56 /* Set precj[j*PREC_G .. j*PREC_G+(PREC_G-1)] to (numsbase, numsbase + gbase, ..., numsbase + (PREC_G-1)*gbase). */ 57 precj[j*g] = numsbase; 58 for (i = 1; i < g; i++) { 59 haskellsecp256k1_v0_1_0_gej_add_var(&precj[j*g + i], &precj[j*g + i - 1], &gbase, NULL); 60 } 61 /* Multiply gbase by PREC_G. */ 62 for (i = 0; i < bits; i++) { 63 haskellsecp256k1_v0_1_0_gej_double_var(&gbase, &gbase, NULL); 64 } 65 /* Multiply numbase by 2. */ 66 haskellsecp256k1_v0_1_0_gej_double_var(&numsbase, &numsbase, NULL); 67 if (j == n - 2) { 68 /* In the last iteration, numsbase is (1 - 2^j) * nums instead. */ 69 haskellsecp256k1_v0_1_0_gej_neg(&numsbase, &numsbase); 70 haskellsecp256k1_v0_1_0_gej_add_var(&numsbase, &numsbase, &nums_gej, NULL); 71 } 72 } 73 haskellsecp256k1_v0_1_0_ge_set_all_gej_var(prec, precj, n * g); 74 free(precj); 75 } 76 for (j = 0; j < n; j++) { 77 for (i = 0; i < g; i++) { 78 haskellsecp256k1_v0_1_0_ge_to_storage(&table[j*g + i], &prec[j*g + i]); 79 } 80 } 81 free(prec); 82 } 83 84 #endif /* SECP256K1_ECMULT_GEN_COMPUTE_TABLE_IMPL_H */