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add bn_zero, bn_bits, bn_lshift, bn_rshift, bn_normalize to bignum

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This commit is contained in:
Pavol Rusnak 2013-09-19 02:54:10 +02:00
parent 65250325c4
commit 1fda6fe339
2 changed files with 60 additions and 11 deletions
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61
bignum.c
View File

@ -64,6 +64,14 @@ void bn_write_be(const bignum256 *in_number, uint8_t *out_number)
}
}
void bn_zero(bignum256 *a)
{
int i;
for (i = 0; i < 9; i++) {
a->val[i] = 0;
}
}
int bn_is_zero(const bignum256 *a)
{
int i;
@ -83,6 +91,34 @@ int bn_is_less(const bignum256 *a, const bignum256 *b)
return 0;
}
int bn_bits(const bignum256 *a) {
int i, r = 0;
for (i = 0; i < 256; i++) {
if (a->val[i / 30] & (1 << (i % 30))) {
r = i;
}
}
return r;
}
void bn_lshift(bignum256 *a)
{
int i;
for (i = 8; i > 0; i--) {
a->val[i] = ((a->val[i] << 1) & 0x3FFFFFFF) | ((a->val[i - 1] & 0x20000000) >> 29);
}
a->val[0] = (a->val[0] << 1) & 0x3FFFFFFF;
}
void bn_rshift(bignum256 *a)
{
int i;
for (i = 0; i < 8; i++) {
a->val[i] = (a->val[i] >> 1) | ((a->val[i + 1] & 1) << 29);
}
a->val[8] >>= 1;
}
// assumes x < 2*prime, result < prime
void bn_mod(bignum256 *x, const bignum256 *prime)
{
@ -93,9 +129,7 @@ void bn_mod(bignum256 *x, const bignum256 *prime)
// if equal
if (i == -1) {
// set x to zero
for (i = 0; i < 9; i++) {
x->val[i] = 0;
}
bn_zero(x);
} else {
// if x is greater
if (x->val[i] > prime->val[i]) {
@ -188,9 +222,7 @@ void bn_inverse(bignum256 *x, const bignum256 *prime)
uint32_t i, j, limb;
bignum256 res;
res.val[0] = 1;
for (i = 1; i < 9; i++) {
res.val[i] = 0;
}
bn_zero(&res);
for (i = 0; i < 9; i++) {
limb = prime->val[i];
// this is not enough in general but fine for secp256k1 because prime->val[0] > 1
@ -383,13 +415,11 @@ void bn_inverse(bignum256 *x, const bignum256 *prime)
}
#endif
void bn_addmod(bignum256 *a, const bignum256 *b, const bignum256 *prime)
{
void bn_normalize(bignum256 *a) {
int i;
uint32_t carry = 0;
for (i = 0; i < 9; i++) {
a->val[i] += b->val[i] + carry;
a->val[i] += carry;
if (a->val[i] > 0x3FFFFFFF) {
carry = a->val[i] >> 30;
a->val[i] &= 0x3FFFFFFF;
@ -397,6 +427,15 @@ void bn_addmod(bignum256 *a, const bignum256 *b, const bignum256 *prime)
carry = 0;
}
}
}
void bn_addmod(bignum256 *a, const bignum256 *b, const bignum256 *prime)
{
int i;
for (i = 0; i < 9; i++) {
a->val[i] += b->val[i];
}
bn_normalize(a);
bn_mod(a, prime);
}
@ -407,7 +446,7 @@ void bn_substract(const bignum256 *a, const bignum256 *b, bignum256 *res)
int i;
uint32_t temp = 0;
for (i = 0; i < 9; i++) {
temp += a->val[i] + 2u *prime256k1.val[i] - b->val[i];
temp += a->val[i] + 2u * prime256k1.val[i] - b->val[i];
res->val[i] = temp & 0x3FFFFFFF;
temp >>= 30;
}

10
bignum.h
View File

@ -50,10 +50,18 @@ void bn_read_be(const uint8_t *in_number, bignum256 *out_number);
void bn_write_be(const bignum256 *in_number, uint8_t *out_number);
void bn_zero(bignum256 *a);
int bn_is_zero(const bignum256 *a);
int bn_is_less(const bignum256 *a, const bignum256 *b);
int bn_bits(const bignum256 *a);
void bn_lshift(bignum256 *a);
void bn_rshift(bignum256 *a);
void bn_mod(bignum256 *x, const bignum256 *prime);
void bn_multiply(const bignum256 *k, bignum256 *x, const bignum256 *prime);
@ -62,6 +70,8 @@ void bn_fast_mod(bignum256 *x, const bignum256 *prime);
void bn_inverse(bignum256 *x, const bignum256 *prime);
void bn_normalize(bignum256 *a);
void bn_addmod(bignum256 *a, const bignum256 *b, const bignum256 *prime);
void bn_substract(const bignum256 *a, const bignum256 *b, bignum256 *res);