ctr.h

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/*
* CTR-BE Mode
* (C) 1999-2007 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#ifndef BOTAN_CTR_BE_H_
#define BOTAN_CTR_BE_H_
 
#include <botan/block_cipher.h>
#include <botan/stream_cipher.h>
 
namespace Botan {
 
/**
* CTR-BE (Counter mode, big-endian)
*/
class CTR_BE final : public StreamCipher {
   public:
      size_t default_iv_length() const override;
 
      bool valid_iv_length(size_t iv_len) const override;
 
      Key_Length_Specification key_spec() const override;
 
      std::string name() const override;
 
      std::unique_ptr<StreamCipher> new_object() const override;
 
      void clear() override;
 
      bool has_keying_material() const override;
 
      size_t buffer_size() const override;
 
      /**
      * @param cipher the block cipher to use
      */
      explicit CTR_BE(std::unique_ptr<BlockCipher> cipher);
 
      CTR_BE(std::unique_ptr<BlockCipher> cipher, size_t ctr_size);
 
      void seek(uint64_t offset) override;
 
      bool supports_seek() const override { return true; }
 
      std::optional<uint64_t> remaining_keystream_bytes() const override;
 
   private:
      void key_schedule(std::span<const uint8_t> key) override;
      void cipher_bytes(const uint8_t in[], uint8_t out[], size_t length) override;
      void generate_keystream(uint8_t out[], size_t length) override;
      void set_iv_bytes(const uint8_t iv[], size_t iv_len) override;
      void add_counter(uint64_t counter);
 
#if defined(BOTAN_HAS_CTR_BE_AVX2)
      size_t ctr_proc_bs16_ctr4_avx2(const uint8_t in[], uint8_t out[], size_t length);
#endif
 
#if defined(BOTAN_HAS_CTR_BE_SIMD32)
      size_t ctr_proc_bs16_ctr4_simd32(const uint8_t in[], uint8_t out[], size_t length);
#endif
 
      std::unique_ptr<BlockCipher> m_cipher;
 
      const size_t m_block_size;
      const size_t m_ctr_size;
      const size_t m_ctr_blocks;
 
      secure_vector<uint8_t> m_counter, m_pad;
      std::vector<uint8_t> m_iv;
      size_t m_pad_pos;
      // Valid only when m_ctr_size < 8: bytes the user can still
      // generate before the narrow counter would wrap.
      uint64_t m_bytes_remaining = 0;
};
 
}  // namespace Botan
 
#endif