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/*
* ChaCha20
* (C) 2014 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#ifndef BOTAN_CHACHA_H_
#define BOTAN_CHACHA_H_
#include <botan/stream_cipher.h>
namespace Botan {
/**
* DJB's ChaCha (https://cr.yp.to/chacha.html)
*/
class BOTAN_PUBLIC_API(2,0) ChaCha final : public StreamCipher
{
public:
/**
* @param rounds number of rounds
* @note Currently only 8, 12 or 20 rounds are supported, all others
* will throw an exception
*/
explicit ChaCha(size_t rounds = 20);
std::string provider() const override;
void cipher(const uint8_t in[], uint8_t out[], size_t length) override;
void write_keystream(uint8_t out[], size_t len) override;
void set_iv(const uint8_t iv[], size_t iv_len) override;
/*
* ChaCha accepts 0, 8, 12 or 24 byte IVs.
* The default IV is a 8 zero bytes.
* An IV of length 0 is treated the same as the default zero IV.
* An IV of length 24 selects XChaCha mode
*/
bool valid_iv_length(size_t iv_len) const override;
size_t default_iv_length() const override;
Key_Length_Specification key_spec() const override;
void clear() override;
StreamCipher* clone() const override;
std::string name() const override;
void seek(uint64_t offset) override;
private:
void key_schedule(const uint8_t key[], size_t key_len) override;
void initialize_state();
void chacha_x4(uint8_t output[64*4], uint32_t state[16], size_t rounds);
#if defined(BOTAN_HAS_CHACHA_SSE2)
void chacha_sse2_x4(uint8_t output[64*4], uint32_t state[16], size_t rounds);
#endif
size_t m_rounds;
secure_vector<uint32_t> m_key;
secure_vector<uint32_t> m_state;
secure_vector<uint8_t> m_buffer;
size_t m_position = 0;
};
}
#endif
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