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// Copyright (c) 2017 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
// Based on the public domain implementation 'merged' by D. J. Bernstein
// See https://cr.yp.to/chacha.html.
#include <crypto/common.h>
#include <crypto/chacha20.h>
#include <string.h>
constexpr static inline uint32_t rotl32(uint32_t v, int c) { return (v << c) | (v >> (32 - c)); }
#define QUARTERROUND(a,b,c,d) \
a += b; d = rotl32(d ^ a, 16); \
c += d; b = rotl32(b ^ c, 12); \
a += b; d = rotl32(d ^ a, 8); \
c += d; b = rotl32(b ^ c, 7);
static const unsigned char sigma[] = "expand 32-byte k";
static const unsigned char tau[] = "expand 16-byte k";
void ChaCha20::SetKey(const unsigned char* k, size_t keylen)
{
const unsigned char *constants;
input[4] = ReadLE32(k + 0);
input[5] = ReadLE32(k + 4);
input[6] = ReadLE32(k + 8);
input[7] = ReadLE32(k + 12);
if (keylen == 32) { /* recommended */
k += 16;
constants = sigma;
} else { /* keylen == 16 */
constants = tau;
}
input[8] = ReadLE32(k + 0);
input[9] = ReadLE32(k + 4);
input[10] = ReadLE32(k + 8);
input[11] = ReadLE32(k + 12);
input[0] = ReadLE32(constants + 0);
input[1] = ReadLE32(constants + 4);
input[2] = ReadLE32(constants + 8);
input[3] = ReadLE32(constants + 12);
input[12] = 0;
input[13] = 0;
input[14] = 0;
input[15] = 0;
}
ChaCha20::ChaCha20()
{
memset(input, 0, sizeof(input));
}
ChaCha20::ChaCha20(const unsigned char* k, size_t keylen)
{
SetKey(k, keylen);
}
void ChaCha20::SetIV(uint64_t iv)
{
input[14] = iv;
input[15] = iv >> 32;
}
void ChaCha20::Seek(uint64_t pos)
{
input[12] = pos;
input[13] = pos >> 32;
}
void ChaCha20::Output(unsigned char* c, size_t bytes)
{
uint32_t x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;
uint32_t j0, j1, j2, j3, j4, j5, j6, j7, j8, j9, j10, j11, j12, j13, j14, j15;
unsigned char *ctarget = nullptr;
unsigned char tmp[64];
unsigned int i;
if (!bytes) return;
j0 = input[0];
j1 = input[1];
j2 = input[2];
j3 = input[3];
j4 = input[4];
j5 = input[5];
j6 = input[6];
j7 = input[7];
j8 = input[8];
j9 = input[9];
j10 = input[10];
j11 = input[11];
j12 = input[12];
j13 = input[13];
j14 = input[14];
j15 = input[15];
for (;;) {
if (bytes < 64) {
ctarget = c;
c = tmp;
}
x0 = j0;
x1 = j1;
x2 = j2;
x3 = j3;
x4 = j4;
x5 = j5;
x6 = j6;
x7 = j7;
x8 = j8;
x9 = j9;
x10 = j10;
x11 = j11;
x12 = j12;
x13 = j13;
x14 = j14;
x15 = j15;
for (i = 20;i > 0;i -= 2) {
QUARTERROUND( x0, x4, x8,x12)
QUARTERROUND( x1, x5, x9,x13)
QUARTERROUND( x2, x6,x10,x14)
QUARTERROUND( x3, x7,x11,x15)
QUARTERROUND( x0, x5,x10,x15)
QUARTERROUND( x1, x6,x11,x12)
QUARTERROUND( x2, x7, x8,x13)
QUARTERROUND( x3, x4, x9,x14)
}
x0 += j0;
x1 += j1;
x2 += j2;
x3 += j3;
x4 += j4;
x5 += j5;
x6 += j6;
x7 += j7;
x8 += j8;
x9 += j9;
x10 += j10;
x11 += j11;
x12 += j12;
x13 += j13;
x14 += j14;
x15 += j15;
++j12;
if (!j12) ++j13;
WriteLE32(c + 0, x0);
WriteLE32(c + 4, x1);
WriteLE32(c + 8, x2);
WriteLE32(c + 12, x3);
WriteLE32(c + 16, x4);
WriteLE32(c + 20, x5);
WriteLE32(c + 24, x6);
WriteLE32(c + 28, x7);
WriteLE32(c + 32, x8);
WriteLE32(c + 36, x9);
WriteLE32(c + 40, x10);
WriteLE32(c + 44, x11);
WriteLE32(c + 48, x12);
WriteLE32(c + 52, x13);
WriteLE32(c + 56, x14);
WriteLE32(c + 60, x15);
if (bytes <= 64) {
if (bytes < 64) {
for (i = 0;i < bytes;++i) ctarget[i] = c[i];
}
input[12] = j12;
input[13] = j13;
return;
}
bytes -= 64;
c += 64;
}
}
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