88 lines
2.9 KiB
Plaintext
88 lines
2.9 KiB
Plaintext
#pragma once
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#include <string.h>
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__device__ void raw_add(unsigned char* x, const unsigned char* p) {
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unsigned short c = 0;
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for (int i = 0; i < 32; i++) {
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c += ((unsigned short)x[i]) + ((unsigned short)p[i]);
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x[i] = (unsigned char)c;
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c >>= 8;
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}
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}
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__device__ void fprime_select(unsigned char* dst, const unsigned char* zero, const unsigned char* one, unsigned char condition) {
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const unsigned char mask = -condition;
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for (int i = 0; i < 32; i++)
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dst[i] = zero[i] ^ (mask & (one[i] ^ zero[i]));
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}
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__device__ void raw_try_sub(unsigned char* x, const unsigned char* p) {
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unsigned char minusp[32];
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unsigned short c = 0;
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for (int i = 0; i < 32; i++) {
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c = ((unsigned short)x[i]) - ((unsigned short)p[i]) - c;
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minusp[i] = (unsigned char)c;
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c = (c >> 8) & 1;
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}
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fprime_select(x, minusp, x, c);
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}
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__device__ int prime_msb(const unsigned char* p) {
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int i;
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unsigned char x;
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for (i = 32 - 1; i >= 0; i--) {
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if (p[i]) break;
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}
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x = p[i];
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i <<= 3;
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while (x) {
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x >>= 1;
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i++;
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}
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return i - 1;
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}
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__device__ void shift_n_bits(unsigned char* x, int n) {
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unsigned short c = 0;
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for (int i = 0; i < 32; i++) {
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c |= ((unsigned short)x[i]) << n;
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x[i] = (unsigned char)c;
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c >>= 8;
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}
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}
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__device__ inline int min_int(int a, int b) {
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return a < b ? a : b;
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}
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__device__ void fprime_from_bytes(unsigned char* n, const unsigned char* x, unsigned long len, const unsigned char* modulus) {
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const int preload_total = min_int(prime_msb(modulus) - 1, (int)(len << 3));
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const int preload_bytes = preload_total >> 3;
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const int preload_bits = preload_total & 7;
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const int rbits = (len << 3) - preload_total;
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memset(n, 0, 32);
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for (int i = 0; i < preload_bytes; i++)
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n[i] = x[len - preload_bytes + i];
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if (preload_bits) {
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shift_n_bits(n, preload_bits);
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n[0] |= x[len - preload_bytes - 1] >> (8 - preload_bits);
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}
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for (int i = rbits - 1; i >= 0; i--) {
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const unsigned char bit = (x[i >> 3] >> (i & 7)) & 1;
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shift_n_bits(n, 1);
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n[0] |= bit;
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raw_try_sub(n, modulus);
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}
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}
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__device__ void fprime_add(unsigned char* r, const unsigned char* a, const unsigned char* modulus) {
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raw_add(r, a);
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raw_try_sub(r, modulus);
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}
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__device__ inline void fprime_copy(unsigned char* x, const unsigned char* a) {
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memcpy(x, a, 32);
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}
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__device__ void fprime_mul(unsigned char* r, const unsigned char* a, const unsigned char* b, const unsigned char* modulus) {
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memset(r, 0, 32);
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for (int i = prime_msb(modulus); i >= 0; i--) {
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const unsigned char bit = (b[i >> 3] >> (i & 7)) & 1;
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unsigned char plusa[32];
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shift_n_bits(r, 1);
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raw_try_sub(r, modulus);
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fprime_copy(plusa, r);
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fprime_add(plusa, a, modulus);
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fprime_select(r, r, plusa, bit);
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}
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} |