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crypto/bn: add method to calculate inv mod and gcd

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Signed-off-by: makejian <makejian@xiaomi.com>
This commit is contained in:
makejian 2023-09-06 20:32:53 +08:00 committed by Xiang Xiao
parent 21514e266a
commit 10168903cc
2 changed files with 204 additions and 2 deletions
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194
crypto/bn.c
View File

@ -514,7 +514,9 @@ void bignum_div(FAR struct bn *a, FAR struct bn *b, FAR struct bn *c)
while (!bignum_is_zero(&current)) /* while (current != 0) */
{
if (bignum_cmp_abs(&tmp, &denom) != SMALLER) /* if (dividend >= denom) */
/* if (dividend >= denom) */
if (bignum_cmp_abs(&tmp, &denom) != SMALLER)
{
bignum_sub_abs(&tmp, &denom, &tmp); /* dividend -= denom; */
bignum_or(c, &current, c); /* answer |= current; */
@ -872,7 +874,9 @@ void pow_mod_faster(FAR struct bn *a, FAR struct bn *b,
while (1)
{
if (tmpb.array[0] & 1) /* if (b % 2) */
/* if (b % 2) */
if (tmpb.array[0] & 1)
{
bignum_mul(res, &tmpa, &tmp); /* r = r * a % m */
bignum_mod(&tmp, n, res);
@ -890,3 +894,189 @@ void pow_mod_faster(FAR struct bn *a, FAR struct bn *b,
bignum_mod(&tmp, n, &tmpa);
}
}
int bignum_lsb(FAR struct bn *a)
{
int i;
int j;
int count;
require(a, "n is null");
for (i = 0, count = 0; i < BN_ARRAY_SIZE; i++)
{
for (j = 0; j < WORD_SIZE * 8; j++, count++)
{
if (((a->array[i] >> j) & 1) != 0)
{
return count;
}
}
}
return 0;
}
void bignum_gcd(FAR struct bn *a, FAR struct bn *b, FAR struct bn *g)
{
size_t lz;
size_t lzt;
struct bn ta;
struct bn tb;
require(a, "a is null");
require(b, "b is null");
require(g, "g is null");
bignum_init(&ta);
bignum_init(&tb);
bignum_assign(&ta, a);
bignum_assign(&tb, b);
lz = bignum_lsb(&ta);
lzt = bignum_lsb(&tb);
if (lzt == 0 && (tb.array[0] & 1) == 0)
{
bignum_assign(g, a);
return;
}
if (lzt < lz)
{
lz = lzt;
}
ta.s = tb.s = 1;
while (bignum_is_zero(&ta) != 1)
{
bignum_rshift(&ta, &ta, bignum_lsb(&ta));
bignum_rshift(&tb, &tb, bignum_lsb(&tb));
if (bignum_cmp(&ta, &tb) >= 0)
{
bignum_sub(&ta, &tb, &ta);
bignum_rshift(&ta, &ta, 1);
}
else
{
bignum_sub(&tb, &ta, &tb);
bignum_rshift(&tb, &tb, 1);
}
}
bignum_lshift(&tb, &tb, lz);
bignum_assign(g, &tb);
}
int bignum_inv_mod(FAR struct bn *a, FAR struct bn *n, FAR struct bn *c)
{
struct bn g;
struct bn ta;
struct bn tu;
struct bn u1;
struct bn u2;
struct bn tb;
struct bn tv;
struct bn v1;
struct bn v2;
struct bn num_one;
struct bn num_zero;
require(a, "a is null");
require(n, "n is null");
require(c, "c is null");
bignum_init(&g);
bignum_init(&ta);
bignum_init(&tu);
bignum_init(&u1);
bignum_init(&u2);
bignum_init(&tb);
bignum_init(&tv);
bignum_init(&v1);
bignum_init(&v2);
bignum_init(&num_one);
bignum_init(&num_zero);
bignum_from_int(&num_one, 1);
if (bignum_cmp(n, &num_one) <= 0)
{
return -EINVAL;
}
bignum_gcd(a, n, &g);
if (bignum_cmp(&g, &num_one) != 0)
{
return -EFAULT;
}
bignum_mod(a, n, &ta);
bignum_assign(&tu, &ta);
bignum_assign(&tb, n);
bignum_assign(&tv, n);
bignum_from_int(&u1, 1);
bignum_from_int(&u2, 0);
bignum_from_int(&v1, 0);
bignum_from_int(&v2, 1);
do
{
while ((tu.array[0] & 1) == 0)
{
bignum_rshift(&tu, &tu, 1);
if ((u1.array[0] & 1) != 0 || (u2.array[0] & 1) != 0)
{
bignum_add(&u1, &tb, &u1);
bignum_sub(&u2, &ta, &u2);
}
bignum_rshift(&u1, &u1, 1);
bignum_rshift(&u2, &u2, 1);
}
while ((tv.array[0] & 1) == 0)
{
bignum_rshift(&tv, &tv, 1);
if ((v1.array[0] & 1) != 0 || (v2.array[0] & 1) != 0)
{
bignum_add(&v1, &tb, &v1);
bignum_sub(&v2, &ta, &v2);
}
bignum_rshift(&v1, &v1, 1);
bignum_rshift(&v2, &v2, 1);
}
if (bignum_cmp(&tu, &tv) >= 0)
{
bignum_sub(&tu, &tv, &tu);
bignum_sub(&u1, &v1, &u1);
bignum_sub(&u2, &v2, &u2);
}
else
{
bignum_sub(&tv, &tu, &tv);
bignum_sub(&v1, &u1, &v1);
bignum_sub(&v2, &u2, &v2);
}
}
while (bignum_is_zero(&tu) != 1);
while (bignum_cmp(&v1, &num_zero) < 0)
{
bignum_add(&v1, n, &v1);
}
while (bignum_cmp(&v1, n) >= 0)
{
bignum_sub(&v1, n, &v1);
}
bignum_assign(c, &v1);
return 0;
}

12
include/crypto/bn.h
View File

@ -224,4 +224,16 @@ void bignum_assign(FAR struct bn *dst, FAR struct bn *src);
void pow_mod_faster(FAR struct bn *a, FAR struct bn *b,
FAR struct bn *n, FAR struct bn *res);
/* Return the number of less significant zero-bits */
int bignum_lsb(FAR struct bn *a);
/* g = gcd(a, b) */
void bignum_gcd(FAR struct bn *a, FAR struct bn *b, FAR struct bn *g);
/* Modular inverse: c = a^-1 mod n */
int bignum_inv_mod(FAR struct bn *a, FAR struct bn *n, FAR struct bn *c);
#endif /* __INCLUDE_CRYPTO_BIGNUM_H */