randombit / botan / 4834822395

/*

* ChaCha20

* (C) 2014,2018 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)

*/

   {

   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;

      /*

      * 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;

      std::unique_ptr<StreamCipher> new_object() const override;

      std::string name() const override;

      void seek(uint64_t offset) override;

      bool has_keying_material() const override;

      size_t buffer_size() const override;

   private:

      void key_schedule(const uint8_t key[], size_t key_len) override;

      void cipher_bytes(const uint8_t in[], uint8_t out[], size_t length) override;

      void generate_keystream(uint8_t out[], size_t len) override;

      void set_iv_bytes(const uint8_t iv[], size_t iv_len) override;

      void initialize_state();

      static size_t parallelism();

      static void chacha(uint8_t output[],

                         size_t output_blocks,

                         uint32_t state[16],

                         size_t rounds);

#if defined(BOTAN_HAS_CHACHA_SIMD32)

      static void chacha_simd32_x4(uint8_t output[64*4], uint32_t state[16], size_t rounds);

#endif

#if defined(BOTAN_HAS_CHACHA_AVX2)

      static void chacha_avx2_x8(uint8_t output[64*8], 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