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// Copyright 2007,2008 Segher Boessenkool <segher@kernel.crashing.org>
// Licensed under the terms of the GNU GPL, version 2
// http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt
#include <cstdio>
#include <string.h>
#include "Common/CommonTypes.h"
#include "Common/Crypto/bn.h"
static void bn_zero(u8* d, u32 n)
{
memset(d, 0, n);
}
static void bn_copy(u8* d, const u8* a, u32 n)
{
memcpy(d, a, n);
}
int bn_compare(const u8* a, const u8* b, u32 n)
{
u32 i;
for (i = 0; i < n; i++) {
if (a[i] < b[i])
return -1;
if (a[i] > b[i])
return 1;
}
return 0;
}
void bn_sub_modulus(u8* a, const u8* N, u32 n)
{
u32 i;
u32 dig;
u8 c;
c = 0;
for (i = n - 1; i < n; i--) {
dig = N[i] + c;
c = (a[i] < dig);
a[i] -= dig;
}
}
void bn_add(u8* d, const u8* a, const u8* b, const u8* N, u32 n)
{
u32 i;
u32 dig;
u8 c;
c = 0;
for (i = n - 1; i < n; i--) {
dig = a[i] + b[i] + c;
c = (dig >= 0x100);
d[i] = dig;
}
if (c)
bn_sub_modulus(d, N, n);
if (bn_compare(d, N, n) >= 0)
bn_sub_modulus(d, N, n);
}
void bn_mul(u8* d, const u8* a, const u8* b, const u8* N, u32 n)
{
u32 i;
u8 mask;
bn_zero(d, n);
for (i = 0; i < n; i++)
for (mask = 0x80; mask != 0; mask >>= 1) {
bn_add(d, d, d, N, n);
if ((a[i] & mask) != 0)
bn_add(d, d, b, N, n);
}
}
void bn_exp(u8* d, const u8* a, const u8* N, u32 n, const u8* e, u32 en)
{
u8 t[512];
u32 i;
u8 mask;
bn_zero(d, n);
d[n-1] = 1;
for (i = 0; i < en; i++)
for (mask = 0x80; mask != 0; mask >>= 1) {
bn_mul(t, d, d, N, n);
if ((e[i] & mask) != 0)
bn_mul(d, t, a, N, n);
else
bn_copy(d, t, n);
}
}
// only for prime N -- stupid but lazy, see if I care
void bn_inv(u8* d, const u8* a, const u8* N, u32 n)
{
u8 t[512], s[512];
bn_copy(t, N, n);
bn_zero(s, n);
s[n-1] = 2;
bn_sub_modulus(t, s, n);
bn_exp(d, a, N, n, t, n);
}
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