source: git/src-cryptopp/gcm.h

// gcm.h - written and placed in the public domain by Wei Dai

//! \file gcm.h
//! \brief GCM block cipher mode of operation
//! \since Crypto++ 5.6.0

#ifndef CRYPTOPP_GCM_H
#define CRYPTOPP_GCM_H

#include "authenc.h"
#include "modes.h"

NAMESPACE_BEGIN(CryptoPP)

//! \enum GCM_TablesOption
//! \brief GCM table size options
enum GCM_TablesOption {
        //! \brief Use a table with 2K entries
        GCM_2K_Tables,
        //! \brief Use a table with 64K entries
        GCM_64K_Tables};

//! \class GCM_Base
//! \brief GCM block cipher base implementation
//! \details Base implementation of the AuthenticatedSymmetricCipher interface
//! \since Crypto++ 5.6.0
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE GCM_Base : public AuthenticatedSymmetricCipherBase
{
public:
        // AuthenticatedSymmetricCipher
        std::string AlgorithmName() const
                {return GetBlockCipher().AlgorithmName() + std::string("/GCM");}
        size_t MinKeyLength() const
                {return GetBlockCipher().MinKeyLength();}
        size_t MaxKeyLength() const
                {return GetBlockCipher().MaxKeyLength();}
        size_t DefaultKeyLength() const
                {return GetBlockCipher().DefaultKeyLength();}
        size_t GetValidKeyLength(size_t n) const
                {return GetBlockCipher().GetValidKeyLength(n);}
        bool IsValidKeyLength(size_t n) const
                {return GetBlockCipher().IsValidKeyLength(n);}
        unsigned int OptimalDataAlignment() const;
        IV_Requirement IVRequirement() const
                {return UNIQUE_IV;}
        unsigned int IVSize() const
                {return 12;}
        unsigned int MinIVLength() const
                {return 1;}
        unsigned int MaxIVLength() const
                {return UINT_MAX;}              // (W64LIT(1)<<61)-1 in the standard
        unsigned int DigestSize() const
                {return 16;}
        lword MaxHeaderLength() const
                {return (W64LIT(1)<<61)-1;}
        lword MaxMessageLength() const
                {return ((W64LIT(1)<<39)-256)/8;}

protected:
        // AuthenticatedSymmetricCipherBase
        bool AuthenticationIsOnPlaintext() const
                {return false;}
        unsigned int AuthenticationBlockSize() const
                {return HASH_BLOCKSIZE;}
        void SetKeyWithoutResync(const byte *userKey, size_t keylength, const NameValuePairs &params);
        void Resync(const byte *iv, size_t len);
        size_t AuthenticateBlocks(const byte *data, size_t len);
        void AuthenticateLastHeaderBlock();
        void AuthenticateLastConfidentialBlock();
        void AuthenticateLastFooterBlock(byte *mac, size_t macSize);
        SymmetricCipher & AccessSymmetricCipher() {return m_ctr;}

        virtual BlockCipher & AccessBlockCipher() =0;
        virtual GCM_TablesOption GetTablesOption() const =0;

        const BlockCipher & GetBlockCipher() const {return const_cast<GCM_Base *>(this)->AccessBlockCipher();};
        byte *HashBuffer() {return m_buffer+REQUIRED_BLOCKSIZE;}
        byte *HashKey() {return m_buffer+2*REQUIRED_BLOCKSIZE;}
        byte *MulTable() {return m_buffer+3*REQUIRED_BLOCKSIZE;}
        inline void ReverseHashBufferIfNeeded();

        class CRYPTOPP_DLL GCTR : public CTR_Mode_ExternalCipher::Encryption
        {
        protected:
                void IncrementCounterBy256();
        };

        GCTR m_ctr;
        static word16 s_reductionTable[256];
        static volatile bool s_reductionTableInitialized;
        enum {REQUIRED_BLOCKSIZE = 16, HASH_BLOCKSIZE = 16};
};

//! \class GCM_Final
//! \brief GCM block cipher final implementation
//! \tparam T_BlockCipher block cipher
//! \tparam T_TablesOption table size, either \p GCM_2K_Tables or \p GCM_64K_Tables
//! \tparam T_IsEncryption direction in which to operate the cipher
//! \since Crypto++ 5.6.0
template <class T_BlockCipher, GCM_TablesOption T_TablesOption, bool T_IsEncryption>
class GCM_Final : public GCM_Base
{
public:
        static std::string StaticAlgorithmName()
                {return T_BlockCipher::StaticAlgorithmName() + std::string("/GCM");}
        bool IsForwardTransformation() const
                {return T_IsEncryption;}

private:
        GCM_TablesOption GetTablesOption() const {return T_TablesOption;}
        BlockCipher & AccessBlockCipher() {return m_cipher;}
        typename T_BlockCipher::Encryption m_cipher;
};

//! \class GCM
//! \brief GCM block cipher mode of operation
//! \tparam T_BlockCipher block cipher
//! \tparam T_TablesOption table size, either \p GCM_2K_Tables or \p GCM_64K_Tables
//! \details \p GCM provides the \p Encryption and \p Decryption typedef. See GCM_Base
//!   and GCM_Final for the AuthenticatedSymmetricCipher implementation.
//! \sa <a href="http://www.cryptolounge.org/wiki/GCM">GCM</a> at the Crypto Lounge
//! \since Crypto++ 5.6.0
template <class T_BlockCipher, GCM_TablesOption T_TablesOption=GCM_2K_Tables>
struct GCM : public AuthenticatedSymmetricCipherDocumentation
{
        typedef GCM_Final<T_BlockCipher, T_TablesOption, true> Encryption;
        typedef GCM_Final<T_BlockCipher, T_TablesOption, false> Decryption;
};

NAMESPACE_END

#endif