159 lines
4.0 KiB
C
159 lines
4.0 KiB
C
#define PY_SSIZE_T_CLEAN
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#include <Python.h>
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#include <stdbool.h>
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#include <gmp.h>
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/*
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C Version by github.com/cartr
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This module adapted from https://github.com/OlegJakushkin/deepblockchains/blob/master/vdf/mimc/python/mimc.py by Sourabh Niyogi https://github.com/sourabhniyogi
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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static mpz_t MODULUS;
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static mpz_t LITTLE_FERMAT_EXPT;
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#define ROUND_CONSTANTS_COUNT 64
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static mpz_t ROUND_CONSTANTS[ROUND_CONSTANTS_COUNT];
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static void
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mimc_init_constants()
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{
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mpz_t fortytwo;
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mpz_init(fortytwo);
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mpz_set_ui(fortytwo, 42);
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// Set MODULUS to hex(2**256 - 2**32 * 351 + 1)
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mpz_init(MODULUS);
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mpz_set_str(MODULUS,
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"ffffffffffffffffffffffffffffffff"
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"fffffffffffffffffffffea100000001",
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16);
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// Set LITTLE_FERMAT_EXPT to hex((MODULUS * 2 - 1) // 3)
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mpz_init(LITTLE_FERMAT_EXPT);
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mpz_set_str(LITTLE_FERMAT_EXPT,
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"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
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"aaaaaaaaaaaaaaaaaaaaa9c0aaaaaaab",
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16);
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// Set all the constants to (i**7 ^ 42)
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for (unsigned long int i = 0; i < ROUND_CONSTANTS_COUNT; i++) {
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mpz_init(ROUND_CONSTANTS[i]);
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mpz_ui_pow_ui(ROUND_CONSTANTS[i], i, 7);
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mpz_xor(ROUND_CONSTANTS[i], ROUND_CONSTANTS[i], fortytwo);
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}
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mpz_clear(fortytwo);
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}
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static bool
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unpack_args(PyObject *args, mpz_t input, unsigned int *steps)
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{
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const char *data_bytes;
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Py_ssize_t count;
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if (!PyArg_ParseTuple(args, "y#I", &data_bytes, &count, steps)) {
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return false;
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}
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mpz_import(input, count, 1, 1, 0, 0, data_bytes);
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return true;
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}
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static PyObject *
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convert_mpz_to_bytes(mpz_t op)
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{
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char string[34];
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size_t size;
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mpz_export(string, &size, 1, 1, 0, 0, op);
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PyObject *result = PyBytes_FromStringAndSize(string, size);
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return result;
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}
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static PyObject *
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forward_mimc(PyObject *_self, PyObject *args)
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{
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mpz_t result;
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unsigned int steps;
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mpz_init(result);
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if (!unpack_args(args, result, &steps)) {
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mpz_clear(result);
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return NULL;
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}
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for (unsigned int i = 1; i < steps; ++i) {
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mpz_powm_ui(result, result, 3, MODULUS);
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mpz_add(result, result, ROUND_CONSTANTS[i % ROUND_CONSTANTS_COUNT]);
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if (mpz_cmp(result, MODULUS) >= 0) {
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mpz_sub(result, result, MODULUS);
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}
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}
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PyObject *result_obj = convert_mpz_to_bytes(result);
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mpz_clear(result);
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return result_obj;
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}
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static PyObject *
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reverse_mimc(PyObject *_self, PyObject *args)
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{
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mpz_t result;
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unsigned int steps;
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mpz_init(result);
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if (!unpack_args(args, result, &steps)) {
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mpz_clear(result);
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return NULL;
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}
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for (unsigned int i = steps - 1; i > 0; --i) {
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mpz_sub(result, result, ROUND_CONSTANTS[i % ROUND_CONSTANTS_COUNT]);
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mpz_powm(result, result, LITTLE_FERMAT_EXPT, MODULUS);
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}
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PyObject *result_obj = convert_mpz_to_bytes(result);
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mpz_clear(result);
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return result_obj;
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}
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static PyMethodDef Methods[] = {
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{"forward_mimc", forward_mimc, METH_VARARGS,
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"Run MIMC forward (the fast direction)"},
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{"reverse_mimc", reverse_mimc, METH_VARARGS,
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"Run MIMC in reverse (the slow direction)"},
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{NULL, NULL, 0, NULL}
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};
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static struct PyModuleDef moduledef = {
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PyModuleDef_HEAD_INIT,
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"native",
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"Fast native implementation of MIMC.",
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-1,
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Methods,
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NULL
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};
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PyMODINIT_FUNC
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PyInit_native()
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{
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mimc_init_constants();
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return PyModule_Create(&moduledef);
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}
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