mirror of https://github.com/bsnes-emu/bsnes.git
79 lines
2.2 KiB
C++
79 lines
2.2 KiB
C++
#pragma once
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#include <nall/arithmetic.hpp>
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namespace nall { namespace Cipher {
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struct ChaCha20 {
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auto initialize(uint256_t key, uint64_t nonce, uint64_t counter = 0) -> void {
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static const uint256_t sigma = 0x6b20657479622d323320646e61707865_u256; //"expand 32-byte k"
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input[ 0] = sigma >> 0;
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input[ 1] = sigma >> 32;
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input[ 2] = sigma >> 64;
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input[ 3] = sigma >> 96;
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input[ 4] = key >> 0;
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input[ 5] = key >> 32;
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input[ 6] = key >> 64;
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input[ 7] = key >> 96;
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input[ 8] = key >> 128;
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input[ 9] = key >> 160;
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input[10] = key >> 192;
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input[11] = key >> 224;
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input[12] = counter >> 0;
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input[13] = counter >> 32;
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input[14] = nonce >> 0;
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input[15] = nonce >> 32;
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offset = 0;
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}
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auto encrypt(const uint8_t* input, uint8_t* output, uint64_t length) -> void {
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while(length--) {
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if(!offset) cipher();
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auto byte = offset++;
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*output++ = *input++ ^ (block[byte >> 2] >> (byte & 3) * 8);
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offset &= 63;
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}
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}
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auto decrypt(const uint8_t* input, uint8_t* output, uint64_t length) -> void {
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encrypt(input, output, length); //reciprocal cipher
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}
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private:
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inline auto rol(uint32_t value, uint bits) -> uint32_t {
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return value << bits | value >> (32 - bits);
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}
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auto quarterRound(uint32_t x[16], uint a, uint b, uint c, uint d) -> void {
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x[a] += x[b]; x[d] = rol(x[d] ^ x[a], 16);
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x[c] += x[d]; x[b] = rol(x[b] ^ x[c], 12);
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x[a] += x[b]; x[d] = rol(x[d] ^ x[a], 8);
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x[c] += x[d]; x[b] = rol(x[b] ^ x[c], 7);
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}
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auto cipher() -> void {
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memory::copy(block, input, 64);
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for(auto n : range(10)) {
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quarterRound(block, 0, 4, 8, 12);
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quarterRound(block, 1, 5, 9, 13);
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quarterRound(block, 2, 6, 10, 14);
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quarterRound(block, 3, 7, 11, 15);
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quarterRound(block, 0, 5, 10, 15);
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quarterRound(block, 1, 6, 11, 12);
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quarterRound(block, 2, 7, 8, 13);
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quarterRound(block, 3, 4, 9, 14);
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}
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for(auto n : range(16)) {
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block[n] += input[n];
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}
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if(!++input[12]) ++input[13];
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}
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uint32_t input[16];
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uint32_t block[16];
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uint64_t offset;
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};
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}}
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