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Second step in converting to C: field

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This commit is contained in:
Pieter Wuille
2013-03-30 22:32:16 +01:00
parent e6d142a8dc
commit 910d0de4e4
9 changed files with 558 additions and 545 deletions
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453
field_5x52.cpp
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@@ -1,18 +1,12 @@
#include <assert.h>
#include <stdint.h>
#include <string>
#include <string.h>
#include "num.h"
#include "field.h"
#include <iostream>
using namespace std;
#ifdef INLINE_ASM
#include "lin64.h"
#endif
namespace secp256k1 {
/** Implements arithmetic modulo FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFE FFFFFC2F,
* represented as 5 uint64_t's in base 2^52. The values are allowed to contain >52 each. In particular,
* each FieldElem has a 'magnitude' associated with it. Internally, a magnitude M means each element
@@ -21,30 +15,17 @@ namespace secp256k1 {
* output.
*/
FieldElem::FieldElem(int x) {
n[0] = x;
n[1] = n[2] = n[3] = n[4] = 0;
#ifdef VERIFY_MAGNITUDE
magnitude = 1;
normalized = true;
#endif
}
FieldElem::FieldElem(const unsigned char *b32) {
SetBytes(b32);
}
void FieldElem::Normalize() {
void static secp256k1_fe_normalize(secp256k1_fe_t *r) {
uint64_t c;
c = n[0];
c = r->n[0];
uint64_t t0 = c & 0xFFFFFFFFFFFFFULL;
c = (c >> 52) + n[1];
c = (c >> 52) + r->n[1];
uint64_t t1 = c & 0xFFFFFFFFFFFFFULL;
c = (c >> 52) + n[2];
c = (c >> 52) + r->n[2];
uint64_t t2 = c & 0xFFFFFFFFFFFFFULL;
c = (c >> 52) + n[3];
c = (c >> 52) + r->n[3];
uint64_t t3 = c & 0xFFFFFFFFFFFFFULL;
c = (c >> 52) + n[4];
c = (c >> 52) + r->n[4];
uint64_t t4 = c & 0x0FFFFFFFFFFFFULL;
c >>= 48;
@@ -60,149 +41,166 @@ void FieldElem::Normalize() {
c = (c >> 52) + t4;
t4 = c & 0x0FFFFFFFFFFFFULL;
// Replace n's with t's if one of the n's overflows.
// If none of the n's overflow to begin with, the t's will just be the n's already and
// we effectively ignore the results of the previous computations.
n[0] = t0; n[1] = t1; n[2] = t2; n[3] = t3; n[4] = t4;
// Subtract p if result >= p
uint64_t mask = -(int64_t)((n[4] < 0xFFFFFFFFFFFFULL) | (n[3] < 0xFFFFFFFFFFFFFULL) | (n[2] < 0xFFFFFFFFFFFFFULL) | (n[1] < 0xFFFFFFFFFFFFFULL) | (n[0] < 0xFFFFEFFFFFC2FULL));
n[4] &= mask;
n[3] &= mask;
n[2] &= mask;
n[1] &= mask;
n[0] -= (~mask & 0xFFFFEFFFFFC2FULL);
uint64_t mask = -(int64_t)((t4 < 0xFFFFFFFFFFFFULL) | (t3 < 0xFFFFFFFFFFFFFULL) | (t2 < 0xFFFFFFFFFFFFFULL) | (t1 < 0xFFFFFFFFFFFFFULL) | (t0 < 0xFFFFEFFFFFC2FULL));
t4 &= mask;
t3 &= mask;
t2 &= mask;
t1 &= mask;
t0 -= (~mask & 0xFFFFEFFFFFC2FULL);
#ifdef VERIFY_MAGNITUDE
magnitude = 1;
normalized = true;
// push internal variables back
r->n[0] = t0; r->n[1] = t1; r->n[2] = t2; r->n[3] = t3; r->n[4] = t4;
#ifdef VERIFY
r->magnitude = 1;
r->normalized = 1;
#endif
}
bool inline FieldElem::IsZero() const {
#ifdef VERIFY_MAGNITUDE
assert(normalized);
void static secp256k1_fe_set_int(secp256k1_fe_t *r, int a) {
r->n[0] = a;
r->n[1] = r->n[2] = r->n[3] = r->n[4] = 0;
#ifdef VERIFY
r->magnitude = 1;
r->normalized = 1;
#endif
return (n[0] == 0 && n[1] == 0 && n[2] == 0 && n[3] == 0 && n[4] == 0);
}
bool inline operator==(const FieldElem &a, const FieldElem &b) {
#ifdef VERIFY_MAGNITUDE
assert(a.normalized);
assert(b.normalized);
// TODO: not constant time!
int static secp256k1_fe_is_zero(const secp256k1_fe_t *a) {
#ifdef VERIFY
assert(a->normalized);
#endif
return (a.n[0] == b.n[0] && a.n[1] == b.n[1] && a.n[2] == b.n[2] && a.n[3] == b.n[3] && a.n[4] == b.n[4]);
return (a->n[0] == 0 && a->n[1] == 0 && a->n[2] == 0 && a->n[3] == 0 && a->n[4] == 0);
}
void FieldElem::GetBytes(unsigned char *o) {
#ifdef VERIFY_MAGNITUDE
assert(normalized);
int static secp256k1_fe_is_odd(const secp256k1_fe_t *a) {
#ifdef VERIFY
assert(a->normalized);
#endif
return a->n[0] & 1;
}
// TODO: not constant time!
int static secp256k1_fe_equal(const secp256k1_fe_t *a, const secp256k1_fe_t *b) {
#ifdef VERIFY
assert(a->normalized);
assert(b->normalized);
#endif
return (a->n[0] == b->n[0] && a->n[1] == b->n[1] && a->n[2] == b->n[2] && a->n[3] == b->n[3] && a->n[4] == b->n[4]);
}
void static secp256k1_fe_set_b32(secp256k1_fe_t *r, const unsigned char *a) {
r->n[0] = r->n[1] = r->n[2] = r->n[3] = r->n[4] = 0;
for (int i=0; i<32; i++) {
for (int j=0; j<2; j++) {
int limb = (8*i+4*j)/52;
int shift = (8*i+4*j)%52;
r->n[limb] |= (uint64_t)((a[31-i] >> (4*j)) & 0xF) << shift;
}
}
#ifdef VERIFY
r->magnitude = 1;
r->normalized = true;
#endif
}
/** Convert a field element to a 32-byte big endian value. Requires the input to be normalized */
void static secp256k1_fe_get_b32(unsigned char *r, const secp256k1_fe_t *a) {
#ifdef VERIFY
assert(a->normalized);
#endif
for (int i=0; i<32; i++) {
int c = 0;
for (int j=0; j<2; j++) {
int limb = (8*i+4*j)/52;
int shift = (8*i+4*j)%52;
c |= ((n[limb] >> shift) & 0xF) << (4 * j);
c |= ((a->n[limb] >> shift) & 0xF) << (4 * j);
}
o[31-i] = c;
r[31-i] = c;
}
}
void FieldElem::SetBytes(const unsigned char *in) {
n[0] = n[1] = n[2] = n[3] = n[4] = 0;
for (int i=0; i<32; i++) {
for (int j=0; j<2; j++) {
int limb = (8*i+4*j)/52;
int shift = (8*i+4*j)%52;
n[limb] |= (uint64_t)((in[31-i] >> (4*j)) & 0xF) << shift;
}
}
#ifdef VERIFY_MAGNITUDE
magnitude = 1;
normalized = true;
void static secp256k1_fe_negate(secp256k1_fe_t *r, const secp256k1_fe_t *a, int m) {
#ifdef VERIFY
assert(a->magnitude <= m);
r->magnitude = m + 1;
r->normalized = 0;
#endif
r->n[0] = 0xFFFFEFFFFFC2FULL * (m + 1) - a->n[0];
r->n[1] = 0xFFFFFFFFFFFFFULL * (m + 1) - a->n[1];
r->n[2] = 0xFFFFFFFFFFFFFULL * (m + 1) - a->n[2];
r->n[3] = 0xFFFFFFFFFFFFFULL * (m + 1) - a->n[3];
r->n[4] = 0x0FFFFFFFFFFFFULL * (m + 1) - a->n[4];
}
void inline FieldElem::SetNeg(const FieldElem &a, int magnitudeIn) {
#ifdef VERIFY_MAGNITUDE
assert(a.magnitude <= magnitudeIn);
magnitude = magnitudeIn + 1;
normalized = false;
void static secp256k1_fe_mul_int(secp256k1_fe_t *r, int a) {
#ifdef VERIFY
r->magnitude *= a;
r->normalized = false;
#endif
n[0] = 0xFFFFEFFFFFC2FULL * (magnitudeIn + 1) - a.n[0];
n[1] = 0xFFFFFFFFFFFFFULL * (magnitudeIn + 1) - a.n[1];
n[2] = 0xFFFFFFFFFFFFFULL * (magnitudeIn + 1) - a.n[2];
n[3] = 0xFFFFFFFFFFFFFULL * (magnitudeIn + 1) - a.n[3];
n[4] = 0x0FFFFFFFFFFFFULL * (magnitudeIn + 1) - a.n[4];
r->n[0] *= a;
r->n[1] *= a;
r->n[2] *= a;
r->n[3] *= a;
r->n[4] *= a;
}
void inline FieldElem::operator*=(int v) {
#ifdef VERIFY_MAGNITUDE
magnitude *= v;
normalized = false;
void static secp256k1_fe_add(secp256k1_fe_t *r, const secp256k1_fe_t *a) {
#ifdef VERIFY
r->magnitude += a->magnitude;
r->normalized = 0;
#endif
n[0] *= v;
n[1] *= v;
n[2] *= v;
n[3] *= v;
n[4] *= v;
r->n[0] += a->n[0];
r->n[1] += a->n[1];
r->n[2] += a->n[2];
r->n[3] += a->n[3];
r->n[4] += a->n[4];
}
void inline FieldElem::operator+=(const FieldElem &a) {
#ifdef VERIFY_MAGNITUDE
magnitude += a.magnitude;
normalized = false;
#endif
n[0] += a.n[0];
n[1] += a.n[1];
n[2] += a.n[2];
n[3] += a.n[3];
n[4] += a.n[4];
}
void FieldElem::SetMult(const FieldElem &a, const FieldElem &b) {
#ifdef VERIFY_MAGNITUDE
assert(a.magnitude <= 8);
assert(b.magnitude <= 8);
void static secp256k1_fe_mul(secp256k1_fe_t *r, const secp256k1_fe_t *a, const secp256k1_fe_t *b) {
#ifdef VERIFY
assert(a->magnitude <= 8);
assert(b->magnitude <= 8);
#endif
#ifdef INLINE_ASM
ExSetMult((uint64_t *) a.n,(uint64_t *) b.n, (uint64_t *) n);
ExSetMult((uint64_t*)a->n, (uint64_t*)b->n, (uint64_t*)r->n);
#else
unsigned __int128 c = (__int128)a.n[0] * b.n[0];
unsigned __int128 c = (__int128)a->n[0] * b->n[0];
uint64_t t0 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 0FFFFFFFFFFFFFE0
c = c + (__int128)a.n[0] * b.n[1] +
(__int128)a.n[1] * b.n[0];
c = c + (__int128)a->n[0] * b->n[1] +
(__int128)a->n[1] * b->n[0];
uint64_t t1 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 20000000000000BF
c = c + (__int128)a.n[0] * b.n[2] +
(__int128)a.n[1] * b.n[1] +
(__int128)a.n[2] * b.n[0];
c = c + (__int128)a->n[0] * b->n[2] +
(__int128)a->n[1] * b->n[1] +
(__int128)a->n[2] * b->n[0];
uint64_t t2 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 30000000000001A0
c = c + (__int128)a.n[0] * b.n[3] +
(__int128)a.n[1] * b.n[2] +
(__int128)a.n[2] * b.n[1] +
(__int128)a.n[3] * b.n[0];
c = c + (__int128)a->n[0] * b->n[3] +
(__int128)a->n[1] * b->n[2] +
(__int128)a->n[2] * b->n[1] +
(__int128)a->n[3] * b->n[0];
uint64_t t3 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 4000000000000280
c = c + (__int128)a.n[0] * b.n[4] +
(__int128)a.n[1] * b.n[3] +
(__int128)a.n[2] * b.n[2] +
(__int128)a.n[3] * b.n[1] +
(__int128)a.n[4] * b.n[0];
c = c + (__int128)a->n[0] * b->n[4] +
(__int128)a->n[1] * b->n[3] +
(__int128)a->n[2] * b->n[2] +
(__int128)a->n[3] * b->n[1] +
(__int128)a->n[4] * b->n[0];
uint64_t t4 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 320000000000037E
c = c + (__int128)a.n[1] * b.n[4] +
(__int128)a.n[2] * b.n[3] +
(__int128)a.n[3] * b.n[2] +
(__int128)a.n[4] * b.n[1];
c = c + (__int128)a->n[1] * b->n[4] +
(__int128)a->n[2] * b->n[3] +
(__int128)a->n[3] * b->n[2] +
(__int128)a->n[4] * b->n[1];
uint64_t t5 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 22000000000002BE
c = c + (__int128)a.n[2] * b.n[4] +
(__int128)a.n[3] * b.n[3] +
(__int128)a.n[4] * b.n[2];
c = c + (__int128)a->n[2] * b->n[4] +
(__int128)a->n[3] * b->n[3] +
(__int128)a->n[4] * b->n[2];
uint64_t t6 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 12000000000001DE
c = c + (__int128)a.n[3] * b.n[4] +
(__int128)a.n[4] * b.n[3];
c = c + (__int128)a->n[3] * b->n[4] +
(__int128)a->n[4] * b->n[3];
uint64_t t7 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 02000000000000FE
c = c + (__int128)a.n[4] * b.n[4];
c = c + (__int128)a->n[4] * b->n[4];
uint64_t t8 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 001000000000001E
uint64_t t9 = c;
@@ -211,52 +209,52 @@ void FieldElem::SetMult(const FieldElem &a, const FieldElem &b) {
c = c + t1 + (__int128)t6 * 0x1000003D10ULL;
t1 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 0000001000003D10
c = c + t2 + (__int128)t7 * 0x1000003D10ULL;
n[2] = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 0000001000003D10
r->n[2] = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 0000001000003D10
c = c + t3 + (__int128)t8 * 0x1000003D10ULL;
n[3] = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 0000001000003D10
r->n[3] = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 0000001000003D10
c = c + t4 + (__int128)t9 * 0x1000003D10ULL;
n[4] = c & 0x0FFFFFFFFFFFFULL; c = c >> 48; // c max 000001000003D110
r->n[4] = c & 0x0FFFFFFFFFFFFULL; c = c >> 48; // c max 000001000003D110
c = t0 + (__int128)c * 0x1000003D1ULL;
n[0] = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 1000008
n[1] = t1 + c;
r->n[0] = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 1000008
r->n[1] = t1 + c;
#endif
#ifdef VERIFY_MAGNITUDE
magnitude = 1;
normalized = false;
#ifdef VERIFY
r->magnitude = 1;
r->normalized = 0;
#endif
}
void FieldElem::SetSquare(const FieldElem &a) {
#ifdef VERIFY_MAGNITUDE
assert(a.magnitude <= 8);
void static secp256k1_fe_sqr(secp256k1_fe_t *r, const secp256k1_fe_t *a) {
#ifdef VERIFY
assert(a->magnitude <= 8);
#endif
#ifdef INLINE_ASM
ExSetSquare((uint64_t *)a.n,(uint64_t *)n);
ExSetSquare((uint64_t*)&a->n, (uint64_t*)&r->n);
#else
__int128 c = (__int128)a.n[0] * a.n[0];
__int128 c = (__int128)a->n[0] * a->n[0];
uint64_t t0 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 0FFFFFFFFFFFFFE0
c = c + (__int128)(a.n[0]*2) * a.n[1];
c = c + (__int128)(a->n[0]*2) * a->n[1];
uint64_t t1 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 20000000000000BF
c = c + (__int128)(a.n[0]*2) * a.n[2] +
(__int128)a.n[1] * a.n[1];
c = c + (__int128)(a->n[0]*2) * a->n[2] +
(__int128)a->n[1] * a->n[1];
uint64_t t2 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 30000000000001A0
c = c + (__int128)(a.n[0]*2) * a.n[3] +
(__int128)(a.n[1]*2) * a.n[2];
c = c + (__int128)(a->n[0]*2) * a->n[3] +
(__int128)(a->n[1]*2) * a->n[2];
uint64_t t3 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 4000000000000280
c = c + (__int128)(a.n[0]*2) * a.n[4] +
(__int128)(a.n[1]*2) * a.n[3] +
(__int128)a.n[2] * a.n[2];
c = c + (__int128)(a->n[0]*2) * a->n[4] +
(__int128)(a->n[1]*2) * a->n[3] +
(__int128)a->n[2] * a->n[2];
uint64_t t4 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 320000000000037E
c = c + (__int128)(a.n[1]*2) * a.n[4] +
(__int128)(a.n[2]*2) * a.n[3];
c = c + (__int128)(a->n[1]*2) * a->n[4] +
(__int128)(a->n[2]*2) * a->n[3];
uint64_t t5 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 22000000000002BE
c = c + (__int128)(a.n[2]*2) * a.n[4] +
(__int128)a.n[3] * a.n[3];
c = c + (__int128)(a->n[2]*2) * a->n[4] +
(__int128)a->n[3] * a->n[3];
uint64_t t6 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 12000000000001DE
c = c + (__int128)(a.n[3]*2) * a.n[4];
c = c + (__int128)(a->n[3]*2) * a->n[4];
uint64_t t7 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 02000000000000FE
c = c + (__int128)a.n[4] * a.n[4];
c = c + (__int128)a->n[4] * a->n[4];
uint64_t t8 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 001000000000001E
uint64_t t9 = c;
c = t0 + (__int128)t5 * 0x1000003D10ULL;
@@ -264,149 +262,18 @@ void FieldElem::SetSquare(const FieldElem &a) {
c = c + t1 + (__int128)t6 * 0x1000003D10ULL;
t1 = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 0000001000003D10
c = c + t2 + (__int128)t7 * 0x1000003D10ULL;
n[2] = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 0000001000003D10
r->n[2] = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 0000001000003D10
c = c + t3 + (__int128)t8 * 0x1000003D10ULL;
n[3] = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 0000001000003D10
r->n[3] = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 0000001000003D10
c = c + t4 + (__int128)t9 * 0x1000003D10ULL;
n[4] = c & 0x0FFFFFFFFFFFFULL; c = c >> 48; // c max 000001000003D110
r->n[4] = c & 0x0FFFFFFFFFFFFULL; c = c >> 48; // c max 000001000003D110
c = t0 + (__int128)c * 0x1000003D1ULL;
n[0] = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 1000008
n[1] = t1 + c;
r->n[0] = c & 0xFFFFFFFFFFFFFULL; c = c >> 52; // c max 1000008
r->n[1] = t1 + c;
#endif
#ifdef VERIFY_MAGNITUDE
assert(a.magnitude <= 8);
normalized = false;
#ifdef VERIFY
assert(a->magnitude <= 8);
a->normalized = 0;
#endif
}
void FieldElem::SetSquareRoot(const FieldElem &a) {
// calculate a^p, with p={15,780,1022,1023}
FieldElem a2; a2.SetSquare(a);
FieldElem a3; a3.SetMult(a2,a);
FieldElem a6; a6.SetSquare(a3);
FieldElem a12; a12.SetSquare(a6);
FieldElem a15; a15.SetMult(a12,a3);
FieldElem a30; a30.SetSquare(a15);
FieldElem a60; a60.SetSquare(a30);
FieldElem a120; a120.SetSquare(a60);
FieldElem a240; a240.SetSquare(a120);
FieldElem a255; a255.SetMult(a240,a15);
FieldElem a510; a510.SetSquare(a255);
FieldElem a750; a750.SetMult(a510,a240);
FieldElem a780; a780.SetMult(a750,a30);
FieldElem a1020; a1020.SetSquare(a510);
FieldElem a1022; a1022.SetMult(a1020,a2);
FieldElem a1023; a1023.SetMult(a1022,a);
FieldElem x = a15;
for (int i=0; i<21; i++) {
for (int j=0; j<10; j++) x.SetSquare(x);
x.SetMult(x,a1023);
}
for (int j=0; j<10; j++) x.SetSquare(x);
x.SetMult(x,a1022);
for (int i=0; i<2; i++) {
for (int j=0; j<10; j++) x.SetSquare(x);
x.SetMult(x,a1023);
}
for (int j=0; j<10; j++) x.SetSquare(x);
SetMult(x,a780);
}
bool FieldElem::IsOdd() const {
#ifdef VERIFY_MAGNITUDE
assert(normalized);
#endif
return n[0] & 1;
}
std::string FieldElem::ToString() {
unsigned char tmp[32];
Normalize();
GetBytes(tmp);
std::string ret;
for (int i=0; i<32; i++) {
static const char *c = "0123456789ABCDEF";
ret += c[(tmp[i] >> 4) & 0xF];
ret += c[(tmp[i]) & 0xF];
}
return ret;
}
void FieldElem::SetHex(const std::string &str) {
unsigned char tmp[32] = {};
static const int cvt[256] = {0, 0, 0, 0, 0, 0, 0,0,0,0,0,0,0,0,0,0,
0, 0, 0, 0, 0, 0, 0,0,0,0,0,0,0,0,0,0,
0, 0, 0, 0, 0, 0, 0,0,0,0,0,0,0,0,0,0,
0, 1, 2, 3, 4, 5, 6,7,8,9,0,0,0,0,0,0,
0,10,11,12,13,14,15,0,0,0,0,0,0,0,0,0,
0, 0, 0, 0, 0, 0, 0,0,0,0,0,0,0,0,0,0,
0,10,11,12,13,14,15,0,0,0,0,0,0,0,0,0,
0, 0, 0, 0, 0, 0, 0,0,0,0,0,0,0,0,0,0,
0, 0, 0, 0, 0, 0, 0,0,0,0,0,0,0,0,0,0,
0, 0, 0, 0, 0, 0, 0,0,0,0,0,0,0,0,0,0,
0, 0, 0, 0, 0, 0, 0,0,0,0,0,0,0,0,0,0,
0, 0, 0, 0, 0, 0, 0,0,0,0,0,0,0,0,0,0,
0, 0, 0, 0, 0, 0, 0,0,0,0,0,0,0,0,0,0,
0, 0, 0, 0, 0, 0, 0,0,0,0,0,0,0,0,0,0,
0, 0, 0, 0, 0, 0, 0,0,0,0,0,0,0,0,0,0,
0, 0, 0, 0, 0, 0, 0,0,0,0,0,0,0,0,0,0};
for (unsigned int i=0; i<32; i++) {
if (str.length() > i*2)
tmp[32 - str.length()/2 + i] = (cvt[(unsigned char)str[2*i]] << 4) + cvt[(unsigned char)str[2*i+1]];
}
SetBytes(tmp);
}
// Nonbuiltin Field Inverse is not constant time.
void FieldElem::SetInverse(FieldElem &a) {
#if defined(USE_FIELDINVERSE_BUILTIN)
// calculate a^p, with p={45,63,1019,1023}
FieldElem a2; a2.SetSquare(a);
FieldElem a3; a3.SetMult(a2,a);
FieldElem a4; a4.SetSquare(a2);
FieldElem a5; a5.SetMult(a4,a);
FieldElem a10; a10.SetSquare(a5);
FieldElem a11; a11.SetMult(a10,a);
FieldElem a21; a21.SetMult(a11,a10);
FieldElem a42; a42.SetSquare(a21);
FieldElem a45; a45.SetMult(a42,a3);
FieldElem a63; a63.SetMult(a42,a21);
FieldElem a126; a126.SetSquare(a63);
FieldElem a252; a252.SetSquare(a126);
FieldElem a504; a504.SetSquare(a252);
FieldElem a1008; a1008.SetSquare(a504);
FieldElem a1019; a1019.SetMult(a1008,a11);
FieldElem a1023; a1023.SetMult(a1019,a4);
FieldElem x = a63;
for (int i=0; i<21; i++) {
for (int j=0; j<10; j++) x.SetSquare(x);
x.SetMult(x,a1023);
}
for (int j=0; j<10; j++) x.SetSquare(x);
x.SetMult(x,a1019);
for (int i=0; i<2; i++) {
for (int j=0; j<10; j++) x.SetSquare(x);
x.SetMult(x,a1023);
}
for (int j=0; j<10; j++) x.SetSquare(x);
SetMult(x,a45);
#else
unsigned char b[32];
a.Normalize();
a.GetBytes(b);
{
const secp256k1_num_t &p = GetFieldConst().field_p;
secp256k1_num_t n;
secp256k1_num_init(&n);
secp256k1_num_set_bin(&n, b, 32);
secp256k1_num_mod_inverse(&n, &n, &p);
secp256k1_num_get_bin(b, 32, &n);
secp256k1_num_free(&n);
}
SetBytes(b);
#endif
}
}