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/*
* GCM Mode
* (C) 2013 Jack Lloyd
* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#ifndef BOTAN_AEAD_GCM_H_
#define BOTAN_AEAD_GCM_H_
#include <botan/aead.h>
#include <botan/sym_algo.h>
namespace Botan {
class BlockCipher;
class StreamCipher;
class GHASH;
/**
* GCM Mode
*/
class GCM_Mode : public AEAD_Mode
{
public:
void set_associated_data(const uint8_t ad[], size_t ad_len) override;
std::string name() const override;
size_t update_granularity() const override;
Key_Length_Specification key_spec() const override;
bool valid_nonce_length(size_t len) const override;
size_t tag_size() const override { return m_tag_size; }
void clear() override;
void reset() override;
std::string provider() const override;
protected:
GCM_Mode(BlockCipher* cipher, size_t tag_size);
~GCM_Mode();
static const size_t GCM_BS = 16;
const size_t m_tag_size;
const std::string m_cipher_name;
std::unique_ptr<StreamCipher> m_ctr;
std::unique_ptr<GHASH> m_ghash;
private:
void start_msg(const uint8_t nonce[], size_t nonce_len) override;
void key_schedule(const uint8_t key[], size_t length) override;
secure_vector<uint8_t> m_y0;
};
/**
* GCM Encryption
*/
class GCM_Encryption final : public GCM_Mode
{
public:
/**
* @param cipher the 128 bit block cipher to use
* @param tag_size is how big the auth tag will be
*/
GCM_Encryption(BlockCipher* cipher, size_t tag_size = 16) :
GCM_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; }
size_t process(uint8_t buf[], size_t size) override;
void finish(secure_vector<uint8_t>& final_block, size_t offset = 0) override;
};
/**
* GCM Decryption
*/
class GCM_Decryption final : public GCM_Mode
{
public:
/**
* @param cipher the 128 bit block cipher to use
* @param tag_size is how big the auth tag will be
*/
GCM_Decryption(BlockCipher* cipher, size_t tag_size = 16) :
GCM_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(); }
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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