Drop in faster C25519 agreement code.
This commit is contained in:
Adam Ierymenko
parent
409406d114
commit
fee6aae442
12 changed files with 733 additions and 45 deletions
718
node/C25519.cpp
718
node/C25519.cpp
|
|
@ -24,15 +24,722 @@ Derived from public domain code by D. J. Bernstein.
|
|||
|
||||
namespace {
|
||||
|
||||
//////////////////////////////////////////////////////////////////////////////
|
||||
//////////////////////////////////////////////////////////////////////////////
|
||||
|
||||
#define crypto_int32 int32_t
|
||||
#define crypto_uint32 uint32_t
|
||||
#define crypto_int64 int64_t
|
||||
#define crypto_uint64 uint64_t
|
||||
#define crypto_hash_sha512_BYTES 64
|
||||
|
||||
//////////////////////////////////////////////////////////////////////////////
|
||||
//////////////////////////////////////////////////////////////////////////////
|
||||
|
||||
typedef uint8_t u8;
|
||||
typedef int32_t s32;
|
||||
typedef int64_t limb;
|
||||
|
||||
static inline void fsum(limb *output, const limb *in) {
|
||||
unsigned i;
|
||||
for (i = 0; i < 10; i += 2) {
|
||||
output[0+i] = output[0+i] + in[0+i];
|
||||
output[1+i] = output[1+i] + in[1+i];
|
||||
}
|
||||
}
|
||||
|
||||
static inline void fdifference(limb *output, const limb *in) {
|
||||
unsigned i;
|
||||
for (i = 0; i < 10; ++i) {
|
||||
output[i] = in[i] - output[i];
|
||||
}
|
||||
}
|
||||
|
||||
static inline void fscalar_product(limb *output, const limb *in, const limb scalar) {
|
||||
unsigned i;
|
||||
for (i = 0; i < 10; ++i) {
|
||||
output[i] = in[i] * scalar;
|
||||
}
|
||||
}
|
||||
|
||||
static inline void fproduct(limb *output, const limb *in2, const limb *in) {
|
||||
output[0] = ((limb) ((s32) in2[0])) * ((s32) in[0]);
|
||||
output[1] = ((limb) ((s32) in2[0])) * ((s32) in[1]) +
|
||||
((limb) ((s32) in2[1])) * ((s32) in[0]);
|
||||
output[2] = 2 * ((limb) ((s32) in2[1])) * ((s32) in[1]) +
|
||||
((limb) ((s32) in2[0])) * ((s32) in[2]) +
|
||||
((limb) ((s32) in2[2])) * ((s32) in[0]);
|
||||
output[3] = ((limb) ((s32) in2[1])) * ((s32) in[2]) +
|
||||
((limb) ((s32) in2[2])) * ((s32) in[1]) +
|
||||
((limb) ((s32) in2[0])) * ((s32) in[3]) +
|
||||
((limb) ((s32) in2[3])) * ((s32) in[0]);
|
||||
output[4] = ((limb) ((s32) in2[2])) * ((s32) in[2]) +
|
||||
2 * (((limb) ((s32) in2[1])) * ((s32) in[3]) +
|
||||
((limb) ((s32) in2[3])) * ((s32) in[1])) +
|
||||
((limb) ((s32) in2[0])) * ((s32) in[4]) +
|
||||
((limb) ((s32) in2[4])) * ((s32) in[0]);
|
||||
output[5] = ((limb) ((s32) in2[2])) * ((s32) in[3]) +
|
||||
((limb) ((s32) in2[3])) * ((s32) in[2]) +
|
||||
((limb) ((s32) in2[1])) * ((s32) in[4]) +
|
||||
((limb) ((s32) in2[4])) * ((s32) in[1]) +
|
||||
((limb) ((s32) in2[0])) * ((s32) in[5]) +
|
||||
((limb) ((s32) in2[5])) * ((s32) in[0]);
|
||||
output[6] = 2 * (((limb) ((s32) in2[3])) * ((s32) in[3]) +
|
||||
((limb) ((s32) in2[1])) * ((s32) in[5]) +
|
||||
((limb) ((s32) in2[5])) * ((s32) in[1])) +
|
||||
((limb) ((s32) in2[2])) * ((s32) in[4]) +
|
||||
((limb) ((s32) in2[4])) * ((s32) in[2]) +
|
||||
((limb) ((s32) in2[0])) * ((s32) in[6]) +
|
||||
((limb) ((s32) in2[6])) * ((s32) in[0]);
|
||||
output[7] = ((limb) ((s32) in2[3])) * ((s32) in[4]) +
|
||||
((limb) ((s32) in2[4])) * ((s32) in[3]) +
|
||||
((limb) ((s32) in2[2])) * ((s32) in[5]) +
|
||||
((limb) ((s32) in2[5])) * ((s32) in[2]) +
|
||||
((limb) ((s32) in2[1])) * ((s32) in[6]) +
|
||||
((limb) ((s32) in2[6])) * ((s32) in[1]) +
|
||||
((limb) ((s32) in2[0])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in2[7])) * ((s32) in[0]);
|
||||
output[8] = ((limb) ((s32) in2[4])) * ((s32) in[4]) +
|
||||
2 * (((limb) ((s32) in2[3])) * ((s32) in[5]) +
|
||||
((limb) ((s32) in2[5])) * ((s32) in[3]) +
|
||||
((limb) ((s32) in2[1])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in2[7])) * ((s32) in[1])) +
|
||||
((limb) ((s32) in2[2])) * ((s32) in[6]) +
|
||||
((limb) ((s32) in2[6])) * ((s32) in[2]) +
|
||||
((limb) ((s32) in2[0])) * ((s32) in[8]) +
|
||||
((limb) ((s32) in2[8])) * ((s32) in[0]);
|
||||
output[9] = ((limb) ((s32) in2[4])) * ((s32) in[5]) +
|
||||
((limb) ((s32) in2[5])) * ((s32) in[4]) +
|
||||
((limb) ((s32) in2[3])) * ((s32) in[6]) +
|
||||
((limb) ((s32) in2[6])) * ((s32) in[3]) +
|
||||
((limb) ((s32) in2[2])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in2[7])) * ((s32) in[2]) +
|
||||
((limb) ((s32) in2[1])) * ((s32) in[8]) +
|
||||
((limb) ((s32) in2[8])) * ((s32) in[1]) +
|
||||
((limb) ((s32) in2[0])) * ((s32) in[9]) +
|
||||
((limb) ((s32) in2[9])) * ((s32) in[0]);
|
||||
output[10] = 2 * (((limb) ((s32) in2[5])) * ((s32) in[5]) +
|
||||
((limb) ((s32) in2[3])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in2[7])) * ((s32) in[3]) +
|
||||
((limb) ((s32) in2[1])) * ((s32) in[9]) +
|
||||
((limb) ((s32) in2[9])) * ((s32) in[1])) +
|
||||
((limb) ((s32) in2[4])) * ((s32) in[6]) +
|
||||
((limb) ((s32) in2[6])) * ((s32) in[4]) +
|
||||
((limb) ((s32) in2[2])) * ((s32) in[8]) +
|
||||
((limb) ((s32) in2[8])) * ((s32) in[2]);
|
||||
output[11] = ((limb) ((s32) in2[5])) * ((s32) in[6]) +
|
||||
((limb) ((s32) in2[6])) * ((s32) in[5]) +
|
||||
((limb) ((s32) in2[4])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in2[7])) * ((s32) in[4]) +
|
||||
((limb) ((s32) in2[3])) * ((s32) in[8]) +
|
||||
((limb) ((s32) in2[8])) * ((s32) in[3]) +
|
||||
((limb) ((s32) in2[2])) * ((s32) in[9]) +
|
||||
((limb) ((s32) in2[9])) * ((s32) in[2]);
|
||||
output[12] = ((limb) ((s32) in2[6])) * ((s32) in[6]) +
|
||||
2 * (((limb) ((s32) in2[5])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in2[7])) * ((s32) in[5]) +
|
||||
((limb) ((s32) in2[3])) * ((s32) in[9]) +
|
||||
((limb) ((s32) in2[9])) * ((s32) in[3])) +
|
||||
((limb) ((s32) in2[4])) * ((s32) in[8]) +
|
||||
((limb) ((s32) in2[8])) * ((s32) in[4]);
|
||||
output[13] = ((limb) ((s32) in2[6])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in2[7])) * ((s32) in[6]) +
|
||||
((limb) ((s32) in2[5])) * ((s32) in[8]) +
|
||||
((limb) ((s32) in2[8])) * ((s32) in[5]) +
|
||||
((limb) ((s32) in2[4])) * ((s32) in[9]) +
|
||||
((limb) ((s32) in2[9])) * ((s32) in[4]);
|
||||
output[14] = 2 * (((limb) ((s32) in2[7])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in2[5])) * ((s32) in[9]) +
|
||||
((limb) ((s32) in2[9])) * ((s32) in[5])) +
|
||||
((limb) ((s32) in2[6])) * ((s32) in[8]) +
|
||||
((limb) ((s32) in2[8])) * ((s32) in[6]);
|
||||
output[15] = ((limb) ((s32) in2[7])) * ((s32) in[8]) +
|
||||
((limb) ((s32) in2[8])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in2[6])) * ((s32) in[9]) +
|
||||
((limb) ((s32) in2[9])) * ((s32) in[6]);
|
||||
output[16] = ((limb) ((s32) in2[8])) * ((s32) in[8]) +
|
||||
2 * (((limb) ((s32) in2[7])) * ((s32) in[9]) +
|
||||
((limb) ((s32) in2[9])) * ((s32) in[7]));
|
||||
output[17] = ((limb) ((s32) in2[8])) * ((s32) in[9]) +
|
||||
((limb) ((s32) in2[9])) * ((s32) in[8]);
|
||||
output[18] = 2 * ((limb) ((s32) in2[9])) * ((s32) in[9]);
|
||||
}
|
||||
|
||||
static inline void freduce_degree(limb *output) {
|
||||
output[8] += output[18] << 4;
|
||||
output[8] += output[18] << 1;
|
||||
output[8] += output[18];
|
||||
output[7] += output[17] << 4;
|
||||
output[7] += output[17] << 1;
|
||||
output[7] += output[17];
|
||||
output[6] += output[16] << 4;
|
||||
output[6] += output[16] << 1;
|
||||
output[6] += output[16];
|
||||
output[5] += output[15] << 4;
|
||||
output[5] += output[15] << 1;
|
||||
output[5] += output[15];
|
||||
output[4] += output[14] << 4;
|
||||
output[4] += output[14] << 1;
|
||||
output[4] += output[14];
|
||||
output[3] += output[13] << 4;
|
||||
output[3] += output[13] << 1;
|
||||
output[3] += output[13];
|
||||
output[2] += output[12] << 4;
|
||||
output[2] += output[12] << 1;
|
||||
output[2] += output[12];
|
||||
output[1] += output[11] << 4;
|
||||
output[1] += output[11] << 1;
|
||||
output[1] += output[11];
|
||||
output[0] += output[10] << 4;
|
||||
output[0] += output[10] << 1;
|
||||
output[0] += output[10];
|
||||
}
|
||||
|
||||
#if (-1 & 3) != 3
|
||||
#error "This code only works on a two's complement system"
|
||||
#endif
|
||||
|
||||
static inline limb div_by_2_26(const limb v)
|
||||
{
|
||||
/* High word of v; no shift needed. */
|
||||
const uint32_t highword = (uint32_t) (((uint64_t) v) >> 32);
|
||||
/* Set to all 1s if v was negative; else set to 0s. */
|
||||
const int32_t sign = ((int32_t) highword) >> 31;
|
||||
/* Set to 0x3ffffff if v was negative; else set to 0. */
|
||||
const int32_t roundoff = ((uint32_t) sign) >> 6;
|
||||
/* Should return v / (1<<26) */
|
||||
return (v + roundoff) >> 26;
|
||||
}
|
||||
|
||||
static inline limb div_by_2_25(const limb v)
|
||||
{
|
||||
/* High word of v; no shift needed*/
|
||||
const uint32_t highword = (uint32_t) (((uint64_t) v) >> 32);
|
||||
/* Set to all 1s if v was negative; else set to 0s. */
|
||||
const int32_t sign = ((int32_t) highword) >> 31;
|
||||
/* Set to 0x1ffffff if v was negative; else set to 0. */
|
||||
const int32_t roundoff = ((uint32_t) sign) >> 7;
|
||||
/* Should return v / (1<<25) */
|
||||
return (v + roundoff) >> 25;
|
||||
}
|
||||
|
||||
static inline void freduce_coefficients(limb *output) {
|
||||
unsigned i;
|
||||
|
||||
output[10] = 0;
|
||||
|
||||
for (i = 0; i < 10; i += 2) {
|
||||
limb over = div_by_2_26(output[i]);
|
||||
/* The entry condition (that |output[i]| < 280*2^54) means that over is, at
|
||||
* most, 280*2^28 in the first iteration of this loop. This is added to the
|
||||
* next limb and we can approximate the resulting bound of that limb by
|
||||
* 281*2^54. */
|
||||
output[i] -= over << 26;
|
||||
output[i+1] += over;
|
||||
|
||||
/* For the first iteration, |output[i+1]| < 281*2^54, thus |over| <
|
||||
* 281*2^29. When this is added to the next limb, the resulting bound can
|
||||
* be approximated as 281*2^54.
|
||||
*
|
||||
* For subsequent iterations of the loop, 281*2^54 remains a conservative
|
||||
* bound and no overflow occurs. */
|
||||
over = div_by_2_25(output[i+1]);
|
||||
output[i+1] -= over << 25;
|
||||
output[i+2] += over;
|
||||
}
|
||||
/* Now |output[10]| < 281*2^29 and all other coefficients are reduced. */
|
||||
output[0] += output[10] << 4;
|
||||
output[0] += output[10] << 1;
|
||||
output[0] += output[10];
|
||||
|
||||
output[10] = 0;
|
||||
|
||||
/* Now output[1..9] are reduced, and |output[0]| < 2^26 + 19*281*2^29
|
||||
* So |over| will be no more than 2^16. */
|
||||
{
|
||||
limb over = div_by_2_26(output[0]);
|
||||
output[0] -= over << 26;
|
||||
output[1] += over;
|
||||
}
|
||||
|
||||
/* Now output[0,2..9] are reduced, and |output[1]| < 2^25 + 2^16 < 2^26. The
|
||||
* bound on |output[1]| is sufficient to meet our needs. */
|
||||
}
|
||||
|
||||
static inline void fmul(limb *output, const limb *in, const limb *in2) {
|
||||
limb t[19];
|
||||
fproduct(t, in, in2);
|
||||
/* |t[i]| < 14*2^54 */
|
||||
freduce_degree(t);
|
||||
freduce_coefficients(t);
|
||||
/* |t[i]| < 2^26 */
|
||||
memcpy(output, t, sizeof(limb) * 10);
|
||||
}
|
||||
|
||||
static inline void fsquare_inner(limb *output, const limb *in) {
|
||||
output[0] = ((limb) ((s32) in[0])) * ((s32) in[0]);
|
||||
output[1] = 2 * ((limb) ((s32) in[0])) * ((s32) in[1]);
|
||||
output[2] = 2 * (((limb) ((s32) in[1])) * ((s32) in[1]) +
|
||||
((limb) ((s32) in[0])) * ((s32) in[2]));
|
||||
output[3] = 2 * (((limb) ((s32) in[1])) * ((s32) in[2]) +
|
||||
((limb) ((s32) in[0])) * ((s32) in[3]));
|
||||
output[4] = ((limb) ((s32) in[2])) * ((s32) in[2]) +
|
||||
4 * ((limb) ((s32) in[1])) * ((s32) in[3]) +
|
||||
2 * ((limb) ((s32) in[0])) * ((s32) in[4]);
|
||||
output[5] = 2 * (((limb) ((s32) in[2])) * ((s32) in[3]) +
|
||||
((limb) ((s32) in[1])) * ((s32) in[4]) +
|
||||
((limb) ((s32) in[0])) * ((s32) in[5]));
|
||||
output[6] = 2 * (((limb) ((s32) in[3])) * ((s32) in[3]) +
|
||||
((limb) ((s32) in[2])) * ((s32) in[4]) +
|
||||
((limb) ((s32) in[0])) * ((s32) in[6]) +
|
||||
2 * ((limb) ((s32) in[1])) * ((s32) in[5]));
|
||||
output[7] = 2 * (((limb) ((s32) in[3])) * ((s32) in[4]) +
|
||||
((limb) ((s32) in[2])) * ((s32) in[5]) +
|
||||
((limb) ((s32) in[1])) * ((s32) in[6]) +
|
||||
((limb) ((s32) in[0])) * ((s32) in[7]));
|
||||
output[8] = ((limb) ((s32) in[4])) * ((s32) in[4]) +
|
||||
2 * (((limb) ((s32) in[2])) * ((s32) in[6]) +
|
||||
((limb) ((s32) in[0])) * ((s32) in[8]) +
|
||||
2 * (((limb) ((s32) in[1])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in[3])) * ((s32) in[5])));
|
||||
output[9] = 2 * (((limb) ((s32) in[4])) * ((s32) in[5]) +
|
||||
((limb) ((s32) in[3])) * ((s32) in[6]) +
|
||||
((limb) ((s32) in[2])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in[1])) * ((s32) in[8]) +
|
||||
((limb) ((s32) in[0])) * ((s32) in[9]));
|
||||
output[10] = 2 * (((limb) ((s32) in[5])) * ((s32) in[5]) +
|
||||
((limb) ((s32) in[4])) * ((s32) in[6]) +
|
||||
((limb) ((s32) in[2])) * ((s32) in[8]) +
|
||||
2 * (((limb) ((s32) in[3])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in[1])) * ((s32) in[9])));
|
||||
output[11] = 2 * (((limb) ((s32) in[5])) * ((s32) in[6]) +
|
||||
((limb) ((s32) in[4])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in[3])) * ((s32) in[8]) +
|
||||
((limb) ((s32) in[2])) * ((s32) in[9]));
|
||||
output[12] = ((limb) ((s32) in[6])) * ((s32) in[6]) +
|
||||
2 * (((limb) ((s32) in[4])) * ((s32) in[8]) +
|
||||
2 * (((limb) ((s32) in[5])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in[3])) * ((s32) in[9])));
|
||||
output[13] = 2 * (((limb) ((s32) in[6])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in[5])) * ((s32) in[8]) +
|
||||
((limb) ((s32) in[4])) * ((s32) in[9]));
|
||||
output[14] = 2 * (((limb) ((s32) in[7])) * ((s32) in[7]) +
|
||||
((limb) ((s32) in[6])) * ((s32) in[8]) +
|
||||
2 * ((limb) ((s32) in[5])) * ((s32) in[9]));
|
||||
output[15] = 2 * (((limb) ((s32) in[7])) * ((s32) in[8]) +
|
||||
((limb) ((s32) in[6])) * ((s32) in[9]));
|
||||
output[16] = ((limb) ((s32) in[8])) * ((s32) in[8]) +
|
||||
4 * ((limb) ((s32) in[7])) * ((s32) in[9]);
|
||||
output[17] = 2 * ((limb) ((s32) in[8])) * ((s32) in[9]);
|
||||
output[18] = 2 * ((limb) ((s32) in[9])) * ((s32) in[9]);
|
||||
}
|
||||
|
||||
static void fsquare(limb *output, const limb *in) {
|
||||
limb t[19];
|
||||
fsquare_inner(t, in);
|
||||
/* |t[i]| < 14*2^54 because the largest product of two limbs will be <
|
||||
* 2^(27+27) and fsquare_inner adds together, at most, 14 of those
|
||||
* products. */
|
||||
freduce_degree(t);
|
||||
freduce_coefficients(t);
|
||||
/* |t[i]| < 2^26 */
|
||||
memcpy(output, t, sizeof(limb) * 10);
|
||||
}
|
||||
|
||||
static inline void fexpand(limb *output, const u8 *input) {
|
||||
#define F(n,start,shift,mask) \
|
||||
output[n] = ((((limb) input[start + 0]) | \
|
||||
((limb) input[start + 1]) << 8 | \
|
||||
((limb) input[start + 2]) << 16 | \
|
||||
((limb) input[start + 3]) << 24) >> shift) & mask;
|
||||
F(0, 0, 0, 0x3ffffff);
|
||||
F(1, 3, 2, 0x1ffffff);
|
||||
F(2, 6, 3, 0x3ffffff);
|
||||
F(3, 9, 5, 0x1ffffff);
|
||||
F(4, 12, 6, 0x3ffffff);
|
||||
F(5, 16, 0, 0x1ffffff);
|
||||
F(6, 19, 1, 0x3ffffff);
|
||||
F(7, 22, 3, 0x1ffffff);
|
||||
F(8, 25, 4, 0x3ffffff);
|
||||
F(9, 28, 6, 0x1ffffff);
|
||||
#undef F
|
||||
}
|
||||
|
||||
#if (-32 >> 1) != -16
|
||||
#error "This code only works when >> does sign-extension on negative numbers"
|
||||
#endif
|
||||
|
||||
static inline s32 s32_eq(s32 a, s32 b) {
|
||||
a = ~(a ^ b);
|
||||
a &= a << 16;
|
||||
a &= a << 8;
|
||||
a &= a << 4;
|
||||
a &= a << 2;
|
||||
a &= a << 1;
|
||||
return a >> 31;
|
||||
}
|
||||
|
||||
static inline s32 s32_gte(s32 a, s32 b) {
|
||||
a -= b;
|
||||
/* a >= 0 iff a >= b. */
|
||||
return ~(a >> 31);
|
||||
}
|
||||
|
||||
static inline void fcontract(u8 *output, limb *input_limbs) {
|
||||
int i;
|
||||
int j;
|
||||
s32 input[10];
|
||||
s32 mask;
|
||||
|
||||
/* |input_limbs[i]| < 2^26, so it's valid to convert to an s32. */
|
||||
for (i = 0; i < 10; i++) {
|
||||
input[i] = input_limbs[i];
|
||||
}
|
||||
|
||||
for (j = 0; j < 2; ++j) {
|
||||
for (i = 0; i < 9; ++i) {
|
||||
if ((i & 1) == 1) {
|
||||
/* This calculation is a time-invariant way to make input[i]
|
||||
* non-negative by borrowing from the next-larger limb. */
|
||||
const s32 mask = input[i] >> 31;
|
||||
const s32 carry = -((input[i] & mask) >> 25);
|
||||
input[i] = input[i] + (carry << 25);
|
||||
input[i+1] = input[i+1] - carry;
|
||||
} else {
|
||||
const s32 mask = input[i] >> 31;
|
||||
const s32 carry = -((input[i] & mask) >> 26);
|
||||
input[i] = input[i] + (carry << 26);
|
||||
input[i+1] = input[i+1] - carry;
|
||||
}
|
||||
}
|
||||
|
||||
/* There's no greater limb for input[9] to borrow from, but we can multiply
|
||||
* by 19 and borrow from input[0], which is valid mod 2^255-19. */
|
||||
{
|
||||
const s32 mask = input[9] >> 31;
|
||||
const s32 carry = -((input[9] & mask) >> 25);
|
||||
input[9] = input[9] + (carry << 25);
|
||||
input[0] = input[0] - (carry * 19);
|
||||
}
|
||||
|
||||
/* After the first iteration, input[1..9] are non-negative and fit within
|
||||
* 25 or 26 bits, depending on position. However, input[0] may be
|
||||
* negative. */
|
||||
}
|
||||
|
||||
/* The first borrow-propagation pass above ended with every limb
|
||||
except (possibly) input[0] non-negative.
|
||||
|
||||
If input[0] was negative after the first pass, then it was because of a
|
||||
carry from input[9]. On entry, input[9] < 2^26 so the carry was, at most,
|
||||
one, since (2**26-1) >> 25 = 1. Thus input[0] >= -19.
|
||||
|
||||
In the second pass, each limb is decreased by at most one. Thus the second
|
||||
borrow-propagation pass could only have wrapped around to decrease
|
||||
input[0] again if the first pass left input[0] negative *and* input[1]
|
||||
through input[9] were all zero. In that case, input[1] is now 2^25 - 1,
|
||||
and this last borrow-propagation step will leave input[1] non-negative. */
|
||||
{
|
||||
const s32 mask = input[0] >> 31;
|
||||
const s32 carry = -((input[0] & mask) >> 26);
|
||||
input[0] = input[0] + (carry << 26);
|
||||
input[1] = input[1] - carry;
|
||||
}
|
||||
|
||||
/* All input[i] are now non-negative. However, there might be values between
|
||||
* 2^25 and 2^26 in a limb which is, nominally, 25 bits wide. */
|
||||
for (j = 0; j < 2; j++) {
|
||||
for (i = 0; i < 9; i++) {
|
||||
if ((i & 1) == 1) {
|
||||
const s32 carry = input[i] >> 25;
|
||||
input[i] &= 0x1ffffff;
|
||||
input[i+1] += carry;
|
||||
} else {
|
||||
const s32 carry = input[i] >> 26;
|
||||
input[i] &= 0x3ffffff;
|
||||
input[i+1] += carry;
|
||||
}
|
||||
}
|
||||
|
||||
{
|
||||
const s32 carry = input[9] >> 25;
|
||||
input[9] &= 0x1ffffff;
|
||||
input[0] += 19*carry;
|
||||
}
|
||||
}
|
||||
|
||||
/* If the first carry-chain pass, just above, ended up with a carry from
|
||||
* input[9], and that caused input[0] to be out-of-bounds, then input[0] was
|
||||
* < 2^26 + 2*19, because the carry was, at most, two.
|
||||
*
|
||||
* If the second pass carried from input[9] again then input[0] is < 2*19 and
|
||||
* the input[9] -> input[0] carry didn't push input[0] out of bounds. */
|
||||
|
||||
/* It still remains the case that input might be between 2^255-19 and 2^255.
|
||||
* In this case, input[1..9] must take their maximum value and input[0] must
|
||||
* be >= (2^255-19) & 0x3ffffff, which is 0x3ffffed. */
|
||||
mask = s32_gte(input[0], 0x3ffffed);
|
||||
for (i = 1; i < 10; i++) {
|
||||
if ((i & 1) == 1) {
|
||||
mask &= s32_eq(input[i], 0x1ffffff);
|
||||
} else {
|
||||
mask &= s32_eq(input[i], 0x3ffffff);
|
||||
}
|
||||
}
|
||||
|
||||
/* mask is either 0xffffffff (if input >= 2^255-19) and zero otherwise. Thus
|
||||
* this conditionally subtracts 2^255-19. */
|
||||
input[0] -= mask & 0x3ffffed;
|
||||
|
||||
for (i = 1; i < 10; i++) {
|
||||
if ((i & 1) == 1) {
|
||||
input[i] -= mask & 0x1ffffff;
|
||||
} else {
|
||||
input[i] -= mask & 0x3ffffff;
|
||||
}
|
||||
}
|
||||
|
||||
input[1] <<= 2;
|
||||
input[2] <<= 3;
|
||||
input[3] <<= 5;
|
||||
input[4] <<= 6;
|
||||
input[6] <<= 1;
|
||||
input[7] <<= 3;
|
||||
input[8] <<= 4;
|
||||
input[9] <<= 6;
|
||||
#define F(i, s) \
|
||||
output[s+0] |= input[i] & 0xff; \
|
||||
output[s+1] = (input[i] >> 8) & 0xff; \
|
||||
output[s+2] = (input[i] >> 16) & 0xff; \
|
||||
output[s+3] = (input[i] >> 24) & 0xff;
|
||||
output[0] = 0;
|
||||
output[16] = 0;
|
||||
F(0,0);
|
||||
F(1,3);
|
||||
F(2,6);
|
||||
F(3,9);
|
||||
F(4,12);
|
||||
F(5,16);
|
||||
F(6,19);
|
||||
F(7,22);
|
||||
F(8,25);
|
||||
F(9,28);
|
||||
#undef F
|
||||
}
|
||||
|
||||
static inline void fmonty(limb *x2, limb *z2, /* output 2Q */
|
||||
limb *x3, limb *z3, /* output Q + Q' */
|
||||
limb *x, limb *z, /* input Q */
|
||||
limb *xprime, limb *zprime, /* input Q' */
|
||||
const limb *qmqp /* input Q - Q' */) {
|
||||
limb origx[10], origxprime[10], zzz[19], xx[19], zz[19], xxprime[19],
|
||||
zzprime[19], zzzprime[19], xxxprime[19];
|
||||
|
||||
memcpy(origx, x, 10 * sizeof(limb));
|
||||
fsum(x, z);
|
||||
/* |x[i]| < 2^27 */
|
||||
fdifference(z, origx); /* does x - z */
|
||||
/* |z[i]| < 2^27 */
|
||||
|
||||
memcpy(origxprime, xprime, sizeof(limb) * 10);
|
||||
fsum(xprime, zprime);
|
||||
/* |xprime[i]| < 2^27 */
|
||||
fdifference(zprime, origxprime);
|
||||
/* |zprime[i]| < 2^27 */
|
||||
fproduct(xxprime, xprime, z);
|
||||
/* |xxprime[i]| < 14*2^54: the largest product of two limbs will be <
|
||||
* 2^(27+27) and fproduct adds together, at most, 14 of those products.
|
||||
* (Approximating that to 2^58 doesn't work out.) */
|
||||
fproduct(zzprime, x, zprime);
|
||||
/* |zzprime[i]| < 14*2^54 */
|
||||
freduce_degree(xxprime);
|
||||
freduce_coefficients(xxprime);
|
||||
/* |xxprime[i]| < 2^26 */
|
||||
freduce_degree(zzprime);
|
||||
freduce_coefficients(zzprime);
|
||||
/* |zzprime[i]| < 2^26 */
|
||||
memcpy(origxprime, xxprime, sizeof(limb) * 10);
|
||||
fsum(xxprime, zzprime);
|
||||
/* |xxprime[i]| < 2^27 */
|
||||
fdifference(zzprime, origxprime);
|
||||
/* |zzprime[i]| < 2^27 */
|
||||
fsquare(xxxprime, xxprime);
|
||||
/* |xxxprime[i]| < 2^26 */
|
||||
fsquare(zzzprime, zzprime);
|
||||
/* |zzzprime[i]| < 2^26 */
|
||||
fproduct(zzprime, zzzprime, qmqp);
|
||||
/* |zzprime[i]| < 14*2^52 */
|
||||
freduce_degree(zzprime);
|
||||
freduce_coefficients(zzprime);
|
||||
/* |zzprime[i]| < 2^26 */
|
||||
memcpy(x3, xxxprime, sizeof(limb) * 10);
|
||||
memcpy(z3, zzprime, sizeof(limb) * 10);
|
||||
|
||||
fsquare(xx, x);
|
||||
/* |xx[i]| < 2^26 */
|
||||
fsquare(zz, z);
|
||||
/* |zz[i]| < 2^26 */
|
||||
fproduct(x2, xx, zz);
|
||||
/* |x2[i]| < 14*2^52 */
|
||||
freduce_degree(x2);
|
||||
freduce_coefficients(x2);
|
||||
/* |x2[i]| < 2^26 */
|
||||
fdifference(zz, xx); // does zz = xx - zz
|
||||
/* |zz[i]| < 2^27 */
|
||||
memset(zzz + 10, 0, sizeof(limb) * 9);
|
||||
fscalar_product(zzz, zz, 121665);
|
||||
/* |zzz[i]| < 2^(27+17) */
|
||||
/* No need to call freduce_degree here:
|
||||
fscalar_product doesn't increase the degree of its input. */
|
||||
freduce_coefficients(zzz);
|
||||
/* |zzz[i]| < 2^26 */
|
||||
fsum(zzz, xx);
|
||||
/* |zzz[i]| < 2^27 */
|
||||
fproduct(z2, zz, zzz);
|
||||
/* |z2[i]| < 14*2^(26+27) */
|
||||
freduce_degree(z2);
|
||||
freduce_coefficients(z2);
|
||||
/* |z2|i| < 2^26 */
|
||||
}
|
||||
|
||||
static inline void swap_conditional(limb a[19], limb b[19], limb iswap) {
|
||||
unsigned i;
|
||||
const s32 swap = (s32) -iswap;
|
||||
|
||||
for (i = 0; i < 10; ++i) {
|
||||
const s32 x = swap & ( ((s32)a[i]) ^ ((s32)b[i]) );
|
||||
a[i] = ((s32)a[i]) ^ x;
|
||||
b[i] = ((s32)b[i]) ^ x;
|
||||
}
|
||||
}
|
||||
|
||||
static inline void cmult(limb *resultx, limb *resultz, const u8 *n, const limb *q) {
|
||||
limb a[19] = {0}, b[19] = {1}, c[19] = {1}, d[19] = {0};
|
||||
limb *nqpqx = a, *nqpqz = b, *nqx = c, *nqz = d, *t;
|
||||
limb e[19] = {0}, f[19] = {1}, g[19] = {0}, h[19] = {1};
|
||||
limb *nqpqx2 = e, *nqpqz2 = f, *nqx2 = g, *nqz2 = h;
|
||||
|
||||
unsigned i, j;
|
||||
|
||||
memcpy(nqpqx, q, sizeof(limb) * 10);
|
||||
|
||||
for (i = 0; i < 32; ++i) {
|
||||
u8 byte = n[31 - i];
|
||||
for (j = 0; j < 8; ++j) {
|
||||
const limb bit = byte >> 7;
|
||||
|
||||
swap_conditional(nqx, nqpqx, bit);
|
||||
swap_conditional(nqz, nqpqz, bit);
|
||||
fmonty(nqx2, nqz2,
|
||||
nqpqx2, nqpqz2,
|
||||
nqx, nqz,
|
||||
nqpqx, nqpqz,
|
||||
q);
|
||||
swap_conditional(nqx2, nqpqx2, bit);
|
||||
swap_conditional(nqz2, nqpqz2, bit);
|
||||
|
||||
t = nqx;
|
||||
nqx = nqx2;
|
||||
nqx2 = t;
|
||||
t = nqz;
|
||||
nqz = nqz2;
|
||||
nqz2 = t;
|
||||
t = nqpqx;
|
||||
nqpqx = nqpqx2;
|
||||
nqpqx2 = t;
|
||||
t = nqpqz;
|
||||
nqpqz = nqpqz2;
|
||||
nqpqz2 = t;
|
||||
|
||||
byte <<= 1;
|
||||
}
|
||||
}
|
||||
|
||||
memcpy(resultx, nqx, sizeof(limb) * 10);
|
||||
memcpy(resultz, nqz, sizeof(limb) * 10);
|
||||
}
|
||||
|
||||
static inline void crecip(limb *out, const limb *z) {
|
||||
limb z2[10];
|
||||
limb z9[10];
|
||||
limb z11[10];
|
||||
limb z2_5_0[10];
|
||||
limb z2_10_0[10];
|
||||
limb z2_20_0[10];
|
||||
limb z2_50_0[10];
|
||||
limb z2_100_0[10];
|
||||
limb t0[10];
|
||||
limb t1[10];
|
||||
int i;
|
||||
|
||||
/* 2 */ fsquare(z2,z);
|
||||
/* 4 */ fsquare(t1,z2);
|
||||
/* 8 */ fsquare(t0,t1);
|
||||
/* 9 */ fmul(z9,t0,z);
|
||||
/* 11 */ fmul(z11,z9,z2);
|
||||
/* 22 */ fsquare(t0,z11);
|
||||
/* 2^5 - 2^0 = 31 */ fmul(z2_5_0,t0,z9);
|
||||
|
||||
/* 2^6 - 2^1 */ fsquare(t0,z2_5_0);
|
||||
/* 2^7 - 2^2 */ fsquare(t1,t0);
|
||||
/* 2^8 - 2^3 */ fsquare(t0,t1);
|
||||
/* 2^9 - 2^4 */ fsquare(t1,t0);
|
||||
/* 2^10 - 2^5 */ fsquare(t0,t1);
|
||||
/* 2^10 - 2^0 */ fmul(z2_10_0,t0,z2_5_0);
|
||||
|
||||
/* 2^11 - 2^1 */ fsquare(t0,z2_10_0);
|
||||
/* 2^12 - 2^2 */ fsquare(t1,t0);
|
||||
/* 2^20 - 2^10 */ for (i = 2;i < 10;i += 2) { fsquare(t0,t1); fsquare(t1,t0); }
|
||||
/* 2^20 - 2^0 */ fmul(z2_20_0,t1,z2_10_0);
|
||||
|
||||
/* 2^21 - 2^1 */ fsquare(t0,z2_20_0);
|
||||
/* 2^22 - 2^2 */ fsquare(t1,t0);
|
||||
/* 2^40 - 2^20 */ for (i = 2;i < 20;i += 2) { fsquare(t0,t1); fsquare(t1,t0); }
|
||||
/* 2^40 - 2^0 */ fmul(t0,t1,z2_20_0);
|
||||
|
||||
/* 2^41 - 2^1 */ fsquare(t1,t0);
|
||||
/* 2^42 - 2^2 */ fsquare(t0,t1);
|
||||
/* 2^50 - 2^10 */ for (i = 2;i < 10;i += 2) { fsquare(t1,t0); fsquare(t0,t1); }
|
||||
/* 2^50 - 2^0 */ fmul(z2_50_0,t0,z2_10_0);
|
||||
|
||||
/* 2^51 - 2^1 */ fsquare(t0,z2_50_0);
|
||||
/* 2^52 - 2^2 */ fsquare(t1,t0);
|
||||
/* 2^100 - 2^50 */ for (i = 2;i < 50;i += 2) { fsquare(t0,t1); fsquare(t1,t0); }
|
||||
/* 2^100 - 2^0 */ fmul(z2_100_0,t1,z2_50_0);
|
||||
|
||||
/* 2^101 - 2^1 */ fsquare(t1,z2_100_0);
|
||||
/* 2^102 - 2^2 */ fsquare(t0,t1);
|
||||
/* 2^200 - 2^100 */ for (i = 2;i < 100;i += 2) { fsquare(t1,t0); fsquare(t0,t1); }
|
||||
/* 2^200 - 2^0 */ fmul(t1,t0,z2_100_0);
|
||||
|
||||
/* 2^201 - 2^1 */ fsquare(t0,t1);
|
||||
/* 2^202 - 2^2 */ fsquare(t1,t0);
|
||||
/* 2^250 - 2^50 */ for (i = 2;i < 50;i += 2) { fsquare(t0,t1); fsquare(t1,t0); }
|
||||
/* 2^250 - 2^0 */ fmul(t0,t1,z2_50_0);
|
||||
|
||||
/* 2^251 - 2^1 */ fsquare(t1,t0);
|
||||
/* 2^252 - 2^2 */ fsquare(t0,t1);
|
||||
/* 2^253 - 2^3 */ fsquare(t1,t0);
|
||||
/* 2^254 - 2^4 */ fsquare(t0,t1);
|
||||
/* 2^255 - 2^5 */ fsquare(t1,t0);
|
||||
/* 2^255 - 21 */ fmul(out,t1,z11);
|
||||
}
|
||||
|
||||
static void crypto_scalarmult(u8 *mypublic, const u8 *secret, const u8 *basepoint) {
|
||||
limb bp[10], x[10], z[11], zmone[10];
|
||||
uint8_t e[32];
|
||||
int i;
|
||||
|
||||
for (i = 0; i < 32; ++i) e[i] = secret[i];
|
||||
e[0] &= 248;
|
||||
e[31] &= 127;
|
||||
e[31] |= 64;
|
||||
|
||||
fexpand(bp, basepoint);
|
||||
cmult(x, z, e, bp);
|
||||
crecip(zmone, z);
|
||||
fmul(z, x, zmone);
|
||||
fcontract(mypublic, z);
|
||||
}
|
||||
|
||||
#if 0
|
||||
void add(unsigned int out[32],const unsigned int a[32],const unsigned int b[32])
|
||||
{
|
||||
unsigned int j;
|
||||
|
|
@ -287,11 +994,12 @@ int crypto_scalarmult(unsigned char *q,const unsigned char *n,const unsigned cha
|
|||
for (i = 0;i < 32;++i) q[i] = work[64 + i];
|
||||
return 0;
|
||||
}
|
||||
#endif
|
||||
|
||||
static const unsigned char base[32] = {9};
|
||||
int crypto_scalarmult_base(unsigned char *q,const unsigned char *n)
|
||||
static inline void crypto_scalarmult_base(unsigned char *q,const unsigned char *n)
|
||||
{
|
||||
return crypto_scalarmult(q,n,base);
|
||||
crypto_scalarmult(q,n,base);
|
||||
}
|
||||
|
||||
//////////////////////////////////////////////////////////////////////////////
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue