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/*
* OCB Mode
* (C) 2013 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#ifndef BOTAN_AEAD_OCB_H__
#define BOTAN_AEAD_OCB_H__
#include <botan/aead.h>
#include <botan/block_cipher.h>
#include <botan/buf_filt.h>
#include <memory>
namespace Botan {
class L_computer;
class Nonce_State;
/**
* OCB Mode (base class for OCB_Encryption and OCB_Decryption). Note
* that OCB is patented, but is freely licensed in some circumstances.
*
* @see "The OCB Authenticated-Encryption Algorithm" internet draft
http://tools.ietf.org/html/draft-irtf-cfrg-ocb-01
* @see Free Licenses http://www.cs.ucdavis.edu/~rogaway/ocb/license.htm
* @see OCB home page http://www.cs.ucdavis.edu/~rogaway/ocb
*/
class BOTAN_DLL OCB_Mode : public AEAD_Mode
{
public:
secure_vector<byte> start(const byte nonce[], size_t nonce_len) override;
void set_associated_data(const byte ad[], size_t ad_len) override;
std::string name() const override;
size_t update_granularity() const;
Key_Length_Specification key_spec() const override;
bool valid_nonce_length(size_t) const override;
void clear();
~OCB_Mode();
protected:
static const size_t BS = 16; // intrinsic to OCB definition
/**
* @param cipher the 128-bit block cipher to use
* @param tag_size is how big the auth tag will be
*/
OCB_Mode(BlockCipher* cipher, size_t tag_size);
void key_schedule(const byte key[], size_t length) override;
size_t tag_size() const { return m_tag_size; }
// fixme make these private
std::unique_ptr<BlockCipher> m_cipher;
std::unique_ptr<L_computer> m_L;
size_t m_tag_size = 0;
size_t m_block_index = 0;
secure_vector<byte> m_ad_hash;
secure_vector<byte> m_offset;
secure_vector<byte> m_checksum;
private:
std::unique_ptr<Nonce_State> m_nonce_state;
};
class BOTAN_DLL OCB_Encryption : public OCB_Mode
{
public:
/**
* @param cipher the 128-bit block cipher to use
* @param tag_size is how big the auth tag will be
*/
OCB_Encryption(BlockCipher* cipher, size_t tag_size = 16) :
OCB_Mode(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; }
void update(secure_vector<byte>& blocks, size_t offset) override;
void finish(secure_vector<byte>& final_block, size_t offset) override;
private:
void encrypt(byte input[], size_t blocks);
};
class BOTAN_DLL OCB_Decryption : public OCB_Mode
{
public:
/**
* @param cipher the 128-bit block cipher to use
* @param tag_size is how big the auth tag will be
*/
OCB_Decryption(BlockCipher* cipher, size_t tag_size = 16) :
OCB_Mode(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(); }
void update(secure_vector<byte>& blocks, size_t offset) override;
void finish(secure_vector<byte>& final_block, size_t offset) override;
private:
void decrypt(byte input[], size_t blocks);
};
}
#endif
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