xts.h

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/*
* XTS mode, from IEEE P1619
* (C) 2009,2013 Jack Lloyd
* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#ifndef BOTAN_MODE_XTS_H_
#define BOTAN_MODE_XTS_H_
 
#include <botan/block_cipher.h>
#include <botan/cipher_mode.h>
 
namespace Botan {
 
/**
* IEEE P1619 XTS Mode
*/
class XTS_Mode : public Cipher_Mode {
   public:
      std::string name() const final;
 
      size_t update_granularity() const final;
 
      size_t ideal_granularity() const final;
 
      size_t minimum_final_size() const final;
 
      Key_Length_Specification key_spec() const final;
 
      size_t default_nonce_length() const final;
 
      bool valid_nonce_length(size_t n) const final;
 
      void clear() final;
 
      void reset() final;
 
      bool has_keying_material() const final;
 
   protected:
      explicit XTS_Mode(std::unique_ptr<BlockCipher> cipher);
 
      const uint8_t* tweak() const { return m_tweak.data(); }
 
      bool tweak_set() const { return !m_tweak.empty(); }
 
      size_t tweak_blocks() const { return m_tweak_blocks; }
 
      const BlockCipher& cipher() const { return *m_cipher; }
 
      void update_tweak(size_t consumed);
 
      size_t cipher_block_size() const { return m_cipher_block_size; }
 
   private:
      void start_msg(const uint8_t nonce[], size_t nonce_len) override;
      void key_schedule(std::span<const uint8_t> key) override;
 
      /*
      * Tweak block update step for XTS
      *
      * Assumes tweak is BS * n bytes long.
      *
      * Assumes that each block of tweak is already set to the successive doublings
      * of the block prior.
      */
      static void update_tweak_block(uint8_t tweak[], size_t BS, size_t blocks_in_tweak);
 
#if defined(BOTAN_HAS_MODE_XTS_AVX512_CLMUL)
      static void update_tweak_block_avx512_clmul(uint8_t tweak[], size_t BS, size_t blocks_in_tweak);
#endif
 
      std::unique_ptr<BlockCipher> m_cipher;
      std::unique_ptr<BlockCipher> m_tweak_cipher;
      secure_vector<uint8_t> m_tweak;
      const size_t m_cipher_block_size;
      const size_t m_cipher_parallelism;
      const size_t m_tweak_blocks;
};
 
/**
* IEEE P1619 XTS Encryption
*/
class XTS_Encryption final : public XTS_Mode {
   public:
      /**
      * @param cipher underlying block cipher
      */
      explicit XTS_Encryption(std::unique_ptr<BlockCipher> cipher) : XTS_Mode(std::move(cipher)) {}
 
      size_t output_length(size_t input_length) const override;
 
   private:
      size_t process_msg(uint8_t buf[], size_t size) override;
      void finish_msg(secure_vector<uint8_t>& final_block, size_t offset = 0) override;
};
 
/**
* IEEE P1619 XTS Decryption
*/
class XTS_Decryption final : public XTS_Mode {
   public:
      /**
      * @param cipher underlying block cipher
      */
      explicit XTS_Decryption(std::unique_ptr<BlockCipher> cipher) : XTS_Mode(std::move(cipher)) {}
 
      size_t output_length(size_t input_length) const override;
 
   private:
      size_t process_msg(uint8_t buf[], size_t size) override;
      void finish_msg(secure_vector<uint8_t>& final_block, size_t offset = 0) override;
};
 
}  // namespace Botan
 
#endif