/*

* OCB Mode

* (C) 2013,2014 Jack Lloyd

* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#ifndef BOTAN_AEAD_OCB_H_

#define BOTAN_AEAD_OCB_H_

#include <botan/aead.h>

#include <botan/block_cipher.h>

namespace Botan {

class L_computer;

/**

* OCB Mode (base class for OCB_Encryption and OCB_Decryption).

* OCB was previously patented in the United States but the patent

* has now been allowed to lapse.

*

* @see "The OCB Authenticated-Encryption Algorithm" RFC 7253

*      https://tools.ietf.org/html/rfc7253

* @see "OCB For Block Ciphers Without 128-Bit Blocks"

*      (draft-krovetz-ocb-wide-d3) for the extension of OCB to

*      block ciphers with larger block sizes.

* @see https://mailarchive.ietf.org/arch/msg/cfrg/qLTveWOdTJcLn4HP3ev-vrj05Vg/

*/

class BOTAN_TEST_API OCB_Mode : public AEAD_Mode {

   public:

      void set_associated_data_n(size_t idx, std::span<const uint8_t> ad) override final;

      std::string name() const override final;

      size_t update_granularity() const override final;

      size_t ideal_granularity() const override final;

      Key_Length_Specification key_spec() const override final;

      bool valid_nonce_length(size_t) const override final;

      size_t tag_size() const override final { return m_tag_size; }

      void clear() override final;

      void reset() override final;

      bool has_keying_material() const override final;

      ~OCB_Mode();

   protected:

      /**

      * @param cipher the block cipher to use

      * @param tag_size is how big the auth tag will be

      */

      OCB_Mode(std::unique_ptr<BlockCipher> cipher, size_t tag_size);

      size_t block_size() const { return m_block_size; }

      size_t par_blocks() const { return m_par_blocks; }

      size_t par_bytes() const { return m_checksum.size(); }

      // fixme make these private

      std::unique_ptr<BlockCipher> m_cipher;

      std::unique_ptr<L_computer> m_L;

      size_t m_block_index = 0;

      secure_vector<uint8_t> m_checksum;

      secure_vector<uint8_t> m_ad_hash;

   private:

      void start_msg(const uint8_t nonce[], size_t nonce_len) override final;

      void key_schedule(std::span<const uint8_t> key) override final;

      const secure_vector<uint8_t>& update_nonce(const uint8_t nonce[], size_t nonce_len);

      const size_t m_tag_size;

      const size_t m_block_size;

      const size_t m_par_blocks;

      secure_vector<uint8_t> m_last_nonce;

      secure_vector<uint8_t> m_stretch;

      secure_vector<uint8_t> m_nonce_buf;

      secure_vector<uint8_t> m_offset;

};

class BOTAN_TEST_API OCB_Encryption final : public OCB_Mode {

   public:

      /**

      * @param cipher the block cipher to use

      * @param tag_size is how big the auth tag will be

      */

      OCB_Encryption(std::unique_ptr<BlockCipher> cipher, size_t tag_size = 16) :

            OCB_Mode(std::move(cipher), tag_size) {}

      size_t output_length(size_t input_length) const override { return input_length + tag_size(); }

      size_t minimum_final_size() const override { return 0; }

   private:

      void encrypt(uint8_t input[], size_t blocks);

      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;

};

class BOTAN_TEST_API OCB_Decryption final : public OCB_Mode {

   public:

      /**

      * @param cipher the block cipher to use

      * @param tag_size is how big the auth tag will be

      */

      OCB_Decryption(std::unique_ptr<BlockCipher> cipher, size_t tag_size = 16) :

            OCB_Mode(std::move(cipher), tag_size) {}

      size_t output_length(size_t input_length) const override {

         BOTAN_ASSERT(input_length >= tag_size(), "Sufficient input");

         return input_length - tag_size();

      }

      size_t minimum_final_size() const override { return tag_size(); }

   private:

      void decrypt(uint8_t input[], size_t blocks);

      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