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/*
* CFB mode
* (C) 1999-2007,2013 Jack Lloyd
* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#ifndef BOTAN_MODE_CFB_H_
#define BOTAN_MODE_CFB_H_
#include <botan/cipher_mode.h>
#include <botan/block_cipher.h>
namespace Botan {
/**
* CFB Mode
*/
class CFB_Mode : public Cipher_Mode
{
public:
std::string name() const override final;
size_t update_granularity() const override final;
size_t minimum_final_size() const override final;
Key_Length_Specification key_spec() const override final;
size_t output_length(size_t input_length) const override final;
size_t default_nonce_length() const override final;
bool valid_nonce_length(size_t n) const override final;
void clear() override final;
void reset() override final;
protected:
CFB_Mode(BlockCipher* cipher, size_t feedback_bits);
void shift_register();
size_t feedback() const { return m_feedback_bytes; }
const BlockCipher& cipher() const { return *m_cipher; }
size_t block_size() const { return m_block_size; }
secure_vector<uint8_t> m_state;
secure_vector<uint8_t> m_keystream;
size_t m_keystream_pos = 0;
private:
void start_msg(const uint8_t nonce[], size_t nonce_len) override;
void key_schedule(const uint8_t key[], size_t length) override;
std::unique_ptr<BlockCipher> m_cipher;
const size_t m_block_size;
const size_t m_feedback_bytes;
};
/**
* CFB Encryption
*/
class CFB_Encryption final : public CFB_Mode
{
public:
/**
* If feedback_bits is zero, cipher->block_size() bytes will be used.
* @param cipher block cipher to use
* @param feedback_bits number of bits fed back into the shift register,
* must be a multiple of 8
*/
CFB_Encryption(BlockCipher* cipher, size_t feedback_bits) :
CFB_Mode(cipher, feedback_bits) {}
size_t process(uint8_t buf[], size_t size) override;
void finish(secure_vector<uint8_t>& final_block, size_t offset = 0) override;
};
/**
* CFB Decryption
*/
class CFB_Decryption final : public CFB_Mode
{
public:
/**
* If feedback_bits is zero, cipher->block_size() bytes will be used.
* @param cipher block cipher to use
* @param feedback_bits number of bits fed back into the shift register,
* must be a multiple of 8
*/
CFB_Decryption(BlockCipher* cipher, size_t feedback_bits) :
CFB_Mode(cipher, feedback_bits) {}
size_t process(uint8_t buf[], size_t size) override;
void finish(secure_vector<uint8_t>& final_block, size_t offset = 0) override;
};
}
#endif
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