91 lines
3.2 KiB
C
91 lines
3.2 KiB
C
/*
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* Copyright (c) Pavol Rusnak, SatoshiLabs
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*
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* Licensed under TREZOR License
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* see LICENSE file for details
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*/
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#include "py/objstr.h"
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#include "bignum.h"
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#include "ssss.h"
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/// def split(m: int, n: int, secret: bytes) -> tuple:
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/// '''
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/// Split secret to (M of N) shares using Shamir's Secret Sharing Scheme.
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/// '''
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STATIC mp_obj_t mod_trezorcrypto_ssss_split(mp_obj_t m_obj, mp_obj_t n_obj, mp_obj_t secret_obj) {
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mp_int_t m = mp_obj_get_int(m_obj);
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mp_int_t n = mp_obj_get_int(n_obj);
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mp_buffer_info_t secret;
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mp_get_buffer_raise(secret_obj, &secret, MP_BUFFER_READ);
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if (secret.len != 32) {
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mp_raise_ValueError("Length of the secret has to be 256 bits");
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}
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if (m < 1 || n < 1 || m > 15 || n > 15 || m > n) {
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mp_raise_ValueError("Invalid number of shares");
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}
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bignum256 sk;
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bignum256 shares[n];
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bn_read_be(secret.buf, &sk);
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if (!ssss_split(&sk, m, n, shares)) {
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mp_raise_ValueError("Error splitting secret");
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}
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mp_obj_tuple_t *tuple = MP_OBJ_TO_PTR(mp_obj_new_tuple(n, NULL));
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vstr_t vstr[n];
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for (int i = 0; i < n; i++) {
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vstr_init_len(&vstr[i], secret.len);
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bn_write_be(&shares[i], secret.buf);
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tuple->items[i] = mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr[i]);
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}
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return MP_OBJ_FROM_PTR(tuple);
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}
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STATIC MP_DEFINE_CONST_FUN_OBJ_3(mod_trezorcrypto_ssss_split_obj, mod_trezorcrypto_ssss_split);
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/// def combine(shares: tuple) -> bytes:
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/// '''
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/// Combine M shares of Shamir's Secret Sharing Scheme into secret.
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/// '''
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STATIC mp_obj_t mod_trezorcrypto_ssss_combine(mp_obj_t shares_obj) {
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size_t n;
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mp_obj_t *share;
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mp_obj_get_array(shares_obj, &n, &share);
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if (n < 1 || n > 15) {
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mp_raise_ValueError("Invalid number of shares");
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}
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bignum256 bnshares[n];
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for (size_t i = 0; i < n; i++) {
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if (MP_OBJ_IS_TYPE(share[i], &mp_type_bytes)) {
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mp_buffer_info_t s;
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mp_get_buffer_raise(share[i], &s, MP_BUFFER_READ);
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if (s.len != 32) {
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mp_raise_ValueError("Length of share has to be 256 bits");
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}
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bn_read_be(s.buf, &bnshares[n]);
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} else {
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memset(&bnshares[i], 0, sizeof(bignum256));
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}
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}
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bignum256 sk;
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if (!ssss_combine(bnshares, n, &sk)) {
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mp_raise_ValueError("Error combining secret");
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}
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vstr_t vstr;
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vstr_init_len(&vstr, 32);
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bn_write_be(&sk, (uint8_t *)vstr.buf);
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return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
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}
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STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorcrypto_ssss_combine_obj, mod_trezorcrypto_ssss_combine);
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STATIC const mp_rom_map_elem_t mod_trezorcrypto_ssss_globals_table[] = {
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{ MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_ssss) },
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{ MP_ROM_QSTR(MP_QSTR_split), MP_ROM_PTR(&mod_trezorcrypto_ssss_split_obj) },
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{ MP_ROM_QSTR(MP_QSTR_combine), MP_ROM_PTR(&mod_trezorcrypto_ssss_combine_obj) },
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};
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STATIC MP_DEFINE_CONST_DICT(mod_trezorcrypto_ssss_globals, mod_trezorcrypto_ssss_globals_table);
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STATIC const mp_obj_module_t mod_trezorcrypto_ssss_module = {
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.base = { &mp_type_module },
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.globals = (mp_obj_dict_t*)&mod_trezorcrypto_ssss_globals,
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};
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