i2pd/libi2pd/ChaCha20.cpp
2018-05-24 14:27:26 -04:00

147 lines
3.0 KiB
C++

#include "ChaCha20.h"
/**
This code is licensed under the MCGSI Public License
Copyright 2018 Jeff Becker
Kovri go write your own code
*/
namespace i2p
{
namespace crypto
{
namespace chacha
{
constexpr int rounds = 20;
constexpr std::size_t blocksize = 64;
void u32t8le(uint32_t v, uint8_t * p)
{
p[0] = v & 0xff;
p[1] = (v >> 8) & 0xff;
p[2] = (v >> 16) & 0xff;
p[3] = (v >> 24) & 0xff;
}
uint32_t u8t32le(const uint8_t * p)
{
uint32_t value = p[3];
value = (value << 8) | p[2];
value = (value << 8) | p[1];
value = (value << 8) | p[0];
return value;
}
uint32_t rotl32(uint32_t x, int n)
{
return x << n | (x >> (-n & 31));
}
void quarterround(uint32_t *x, int a, int b, int c, int d)
{
x[a] += x[b]; x[d] = rotl32(x[d] ^ x[a], 16);
x[c] += x[d]; x[b] = rotl32(x[b] ^ x[c], 12);
x[a] += x[b]; x[d] = rotl32(x[d] ^ x[a], 8);
x[c] += x[d]; x[b] = rotl32(x[b] ^ x[c], 7);
}
struct State_t
{
State_t() {};
State_t(State_t &&) = delete;
State_t & operator += (const State_t & other)
{
for(int i = 0; i < 16; i++)
data[i] += other.data[i];
return *this;
}
void Copy(const State_t & other)
{
memcpy(data, other.data, sizeof(uint32_t) * 16);
}
uint32_t data[16];
};
struct Block_t
{
Block_t() {};
Block_t(Block_t &&) = delete;
uint8_t data[blocksize];
void operator << (const State_t & st)
{
int i;
for (i = 0; i < 16; i++)
u32t8le(st.data[i], data + (i << 2));
}
};
void block(const State_t &input, Block_t & block, int rounds)
{
int i;
State_t x;
x.Copy(input);
for (i = rounds; i > 0; i -= 2)
{
quarterround(x.data, 0, 4, 8, 12);
quarterround(x.data, 1, 5, 9, 13);
quarterround(x.data, 2, 6, 10, 14);
quarterround(x.data, 3, 7, 11, 15);
quarterround(x.data, 0, 5, 10, 15);
quarterround(x.data, 1, 6, 11, 12);
quarterround(x.data, 2, 7, 8, 13);
quarterround(x.data, 3, 4, 9, 14);
}
x += input;
block << x;
}
} // namespace chacha
void chacha20(uint8_t * buf, size_t sz, const uint8_t * nonce, const uint8_t * key, uint32_t counter)
{
chacha::State_t state;
chacha::Block_t block;
size_t i, j;
state.data[0] = 0x61707865;
state.data[1] = 0x3320646e;
state.data[2] = 0x79622d32;
state.data[3] = 0x6b206574;
for (i = 0; i < 8; i++)
state.data[4 + i] = chacha::u8t32le(key + i * 4);
state.data[12] = counter;
for (i = 0; i < 3; i++)
state.data[13 + i] = chacha::u8t32le(nonce + i * 4);
for (i = 0; i < sz; i += chacha::blocksize)
{
chacha::block(state, block, chacha::rounds);
state.data[12]++;
for (j = i; j < i + chacha::blocksize; j++)
{
if (j >= sz) break;
buf[j] ^= block.data[j - i];
}
}
}
}
}