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/*
* ecgen, tool for generating Elliptic curve domain parameters
* Copyright (C) 2017 J08nY
*/
#include "brainpool.h"
#include "gen/seed.h"
#include "io/output.h"
#include "util/bits.h"
#include "util/str.h"
#include "util/memory.h"
static seed_t *brainpool_new() {
seed_t *result = seed_new();
result->type = SEED_BRAINPOOL;
result->brainpool.first = true;
return result;
}
static void seed_wv(seed_t *seed) {
pari_sp ltop = avma;
GEN L = utoi(cfg->bits);
seed->brainpool.v = itou(gfloor(gdivgs(subis(L, 1), 160)));
seed->brainpool.w =
itou(subis(subis(L, 160 * seed->brainpool.v), 1));
avma = ltop;
}
static void brainpool_update_seed(bits_t *s) {
pari_sp ltop = avma;
GEN z = bits_to_i(s);
GEN t = Fp_add(z, gen_1, int2n(160));
bits_t *result = bits_from_i_len(t, 160);
avma = ltop;
bits_cpy(s, result);
bits_free(&result);
}
static bits_t *brainpool_hash(const bits_t *s, long w, long v) {
pari_sp ltop = avma;
unsigned char h0[20];
bits_sha1(s, h0);
unsigned char hashout[w + 20 * v];
memcpy(hashout, h0, (size_t)w);
GEN z = bits_to_i(s);
GEN m = int2n(160);
for (long i = 1; i < v; ++i) {
bits_t *si = bits_from_i(Fp_add(z, stoi(i), m));
bits_sha1(si, hashout + w + 20 * i);
bits_free(&si);
}
bits_t *result = bits_from_raw(hashout, (size_t)(w + (20 * v)));
avma = ltop;
return result;
}
bool brainpool_seed_valid(const char *hex_str) {
const char *seed = str_is_hex(hex_str);
return seed && strlen(seed) == 40;
}
GENERATOR(brainpool_gen_seed_random) {
seed_t *seed = brainpool_new();
seed->seed = bits_new_rand(160);
seed_wv(seed);
curve->seed = seed;
return 1;
}
GENERATOR(brainpool_gen_seed_argument) {
seed_t *seed = brainpool_new();
seed->seed = bits_from_hex(str_is_hex(cfg->seed));
seed_wv(seed);
curve->seed = seed;
return 1;
}
GENERATOR(brainpool_gen_seed_input) {
pari_sp ltop = avma;
GEN str = input_string("seed:");
const char *cstr = GSTR(str);
if (!brainpool_seed_valid(cstr)) {
fprintf(err, "SEED must be exactly 160 bits(40 hex characters).\n");
avma = ltop;
return 0;
}
seed_t *seed = brainpool_new();
seed->seed = bits_from_hex(str_is_hex(cstr));
seed_wv(seed);
curve->seed = seed;
return 1;
}
GENERATOR(brainpool_gen_equation) {
// field is definitely prime
pari_sp btop = avma;
seed_t *seed = curve->seed;
do {
if (seed->brainpool.first) {
brainpool_update_seed(seed->seed);
seed->brainpool.first = false;
}
GEN z;
bits_t *a_bits =
brainpool_hash(seed->seed, seed->brainpool.w, seed->brainpool.v);
GEN a = bits_to_i(a_bits);
bits_free(&a_bits);
z = Fp_sqrtn(a, stoi(4), curve->field, NULL);
if (z == NULL) {
brainpool_update_seed(seed->seed);
avma = btop;
continue;
}
seed->brainpool.seed_a = bits_copy(seed->seed);
brainpool_update_seed(seed->seed);
bits_t *b_bits =
brainpool_hash(seed->seed, seed->brainpool.w, seed->brainpool.v);
GEN b = bits_to_i(b_bits);
bits_free(&b_bits);
if (!Fp_issquare(b, curve->field)) {
brainpool_update_seed(seed->seed);
bits_free(&seed->brainpool.seed_a);
avma = btop;
continue;
}
seed->brainpool.seed_b = bits_copy(seed->seed);
GEN mod_a = gmodulo(a, curve->field);
GEN mod_b = gmodulo(b, curve->field);
if (gequal0(gmulsg(-16, gadd(gmulsg(4, gpowgs(mod_a, 3)),
gmulsg(27, gsqr(mod_b)))))) {
brainpool_update_seed(seed->seed);
bits_free(&seed->brainpool.seed_a);
bits_free(&seed->brainpool.seed_b);
avma = btop;
continue;
}
brainpool_update_seed(seed->seed);
seed->brainpool.seed_bp = bits_copy(seed->seed);
bits_t *mult_bits =
brainpool_hash(seed->seed, seed->brainpool.w, seed->brainpool.v);
seed->brainpool.mult = bits_to_i(mult_bits);
curve->a = mod_a;
curve->b = mod_b;
gerepileall(btop, 2, &curve->a, &curve->b);
break;
} while (true);
return 1;
}
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