hbc/pywii/ecmodule/_ecmodule.c

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2016-11-23 06:35:12 +01:00
// Copyright 2007,2008 Segher Boessenkool <segher@kernel.crashing.org>
// Copyright 2008 Hector Martin <marcan@marcansoft.com>
// Licensed under the terms of the GNU GPL, version 2
// http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt
#include "Python.h"
#include <stdint.h>
typedef uint8_t u8;
typedef uint32_t u32;
/* ----------------------------------------------------- */
static void elt_copy(u8 *d, const u8 *a)
{
memcpy(d, a, 30);
}
static void elt_zero(u8 *d)
{
memset(d, 0, 30);
}
static int elt_is_zero(const u8 *d)
{
u32 i;
for (i = 0; i < 30; i++)
if (d[i] != 0)
return 0;
return 1;
}
static void elt_add(u8 *d, const u8 *a, const u8 *b)
{
u32 i;
for (i = 0; i < 30; i++)
d[i] = a[i] ^ b[i];
}
static void elt_mul_x(u8 *d, const u8 *a)
{
u8 carry, x, y;
u32 i;
carry = a[0] & 1;
x = 0;
for (i = 0; i < 29; i++) {
y = a[i + 1];
d[i] = x ^ (y >> 7);
x = y << 1;
}
d[29] = x ^ carry;
d[20] ^= carry << 2;
}
static void elt_mul(u8 *d, const u8 *a, const u8 *b)
{
u32 i, n;
u8 mask;
elt_zero(d);
i = 0;
mask = 1;
for (n = 0; n < 233; n++) {
elt_mul_x(d, d);
if ((a[i] & mask) != 0)
elt_add(d, d, b);
mask >>= 1;
if (mask == 0) {
mask = 0x80;
i++;
}
}
}
static const u8 square[16] =
"\x00\x01\x04\x05\x10\x11\x14\x15\x40\x41\x44\x45\x50\x51\x54\x55";
static void elt_square_to_wide(u8 *d, const u8 *a)
{
u32 i;
for (i = 0; i < 30; i++) {
d[2*i] = square[a[i] >> 4];
d[2*i + 1] = square[a[i] & 15];
}
}
static void wide_reduce(u8 *d)
{
u32 i;
u8 x;
for (i = 0; i < 30; i++) {
x = d[i];
d[i + 19] ^= x >> 7;
d[i + 20] ^= x << 1;
d[i + 29] ^= x >> 1;
d[i + 30] ^= x << 7;
}
x = d[30] & ~1;
d[49] ^= x >> 7;
d[50] ^= x << 1;
d[59] ^= x >> 1;
d[30] &= 1;
}
static void elt_square(u8 *d, const u8 *a)
{
u8 wide[60];
elt_square_to_wide(wide, a);
wide_reduce(wide);
elt_copy(d, wide + 30);
}
static void itoh_tsujii(u8 *d, const u8 *a, const u8 *b, u32 j)
{
u8 t[30];
elt_copy(t, a);
while (j--) {
elt_square(d, t);
elt_copy(t, d);
}
elt_mul(d, t, b);
}
static void elt_inv(u8 *d, const u8 *a)
{
u8 t[30];
u8 s[30];
itoh_tsujii(t, a, a, 1);
itoh_tsujii(s, t, a, 1);
itoh_tsujii(t, s, s, 3);
itoh_tsujii(s, t, a, 1);
itoh_tsujii(t, s, s, 7);
itoh_tsujii(s, t, t, 14);
itoh_tsujii(t, s, a, 1);
itoh_tsujii(s, t, t, 29);
itoh_tsujii(t, s, s, 58);
itoh_tsujii(s, t, t, 116);
elt_square(d, s);
}
/* ----------------------------------------------------- */
static PyObject *
_ec_elt_mul(PyObject *self /* Not used */, PyObject *args)
{
const char *a, *b;
char d[30];
int la, lb;
if (!PyArg_ParseTuple(args, "s#s#", &a, &la, &b, &lb))
return NULL;
if(la != 30 || lb != 30) {
PyErr_SetString(PyExc_ValueError, "ELT lengths must be 30");
return NULL;
}
elt_mul(d,a,b);
return Py_BuildValue("s#", d, 30);
}
static PyObject *
_ec_elt_inv(PyObject *self /* Not used */, PyObject *args)
{
const char *a;
char d[30];
int la;
if (!PyArg_ParseTuple(args, "s#", &a, &la))
return NULL;
if(la != 30) {
PyErr_SetString(PyExc_ValueError, "ELT length must be 30");
return NULL;
}
elt_inv(d,a);
return Py_BuildValue("s#", d, 30);
}
static PyObject *
_ec_elt_square(PyObject *self /* Not used */, PyObject *args)
{
const char *a;
char d[30];
int la;
if (!PyArg_ParseTuple(args, "s#", &a, &la))
return NULL;
if(la != 30) {
PyErr_SetString(PyExc_ValueError, "ELT length must be 30");
return NULL;
}
elt_square(d,a);
return Py_BuildValue("s#", d, 30);
}
/* List of methods defined in the module */
static struct PyMethodDef _ec_methods[] = {
{"elt_mul", (PyCFunction)_ec_elt_mul, METH_VARARGS, "Multiply two ELTs"},
{"elt_inv", (PyCFunction)_ec_elt_inv, METH_VARARGS, "Take the inverse of an ELT"},
{"elt_square", (PyCFunction)_ec_elt_square, METH_VARARGS, "Efficiently square an ELT"},
{NULL, (PyCFunction)NULL, 0, NULL} /* sentinel */
};
/* Initialization function for the module (*must* be called init_ec) */
static char _ec_module_documentation[] =
"Faster C versions of some ELT functions"
;
void
init_ec()
{
PyObject *m, *d;
/* Create the module and add the functions */
m = Py_InitModule4("_ec", _ec_methods,
_ec_module_documentation,
(PyObject*)NULL,PYTHON_API_VERSION);
/* Check for errors */
if (PyErr_Occurred())
Py_FatalError("can't initialize module _ec");
}