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// Copyright (c) 2017-2022 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#ifndef BITCOIN_CRYPTO_CHACHA20_H
#define BITCOIN_CRYPTO_CHACHA20_H
#include <cstdlib>
#include <stdint.h>
// classes for ChaCha20 256-bit stream cipher developed by Daniel J. Bernstein
// https://cr.yp.to/chacha/chacha-20080128.pdf */
/** ChaCha20 cipher that only operates on multiples of 64 bytes. */
class ChaCha20Aligned
{
private:
uint32_t input[12];
public:
ChaCha20Aligned();
/** Initialize a cipher with specified 32-byte key. */
ChaCha20Aligned(const unsigned char* key32);
/** set 32-byte key. */
void SetKey32(const unsigned char* key32);
/** set the 64-bit nonce. */
void SetIV(uint64_t iv);
/** set the 64bit block counter (pos seeks to byte position 64*pos). */
void Seek64(uint64_t pos);
/** outputs the keystream of size <64*blocks> into <c> */
void Keystream64(unsigned char* c, size_t blocks);
/** enciphers the message <input> of length <64*blocks> and write the enciphered representation into <output>
* Used for encryption and decryption (XOR)
*/
void Crypt64(const unsigned char* input, unsigned char* output, size_t blocks);
};
/** Unrestricted ChaCha20 cipher. */
class ChaCha20
{
private:
ChaCha20Aligned m_aligned;
unsigned char m_buffer[64] = {0};
unsigned m_bufleft{0};
public:
ChaCha20() = default;
/** Initialize a cipher with specified 32-byte key. */
ChaCha20(const unsigned char* key32) : m_aligned(key32) {}
/** set 32-byte key. */
void SetKey32(const unsigned char* key32)
{
m_aligned.SetKey32(key32);
m_bufleft = 0;
}
/** set the 64-bit nonce. */
void SetIV(uint64_t iv) { m_aligned.SetIV(iv); }
/** set the 64bit block counter (pos seeks to byte position 64*pos). */
void Seek64(uint64_t pos)
{
m_aligned.Seek64(pos);
m_bufleft = 0;
}
/** outputs the keystream of size <bytes> into <c> */
void Keystream(unsigned char* c, size_t bytes);
/** enciphers the message <input> of length <bytes> and write the enciphered representation into <output>
* Used for encryption and decryption (XOR)
*/
void Crypt(const unsigned char* input, unsigned char* output, size_t bytes);
};
#endif // BITCOIN_CRYPTO_CHACHA20_H
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