gcm.h

Go to the documentation of this file.

// gcm.h - originally written and placed in the public domain by Wei Dai
 
 
#ifndef CRYPTOPP_GCM_H
#define CRYPTOPP_GCM_H
 
#include "authenc.h"
#include "modes.h"
 
// Clang 3.3 integrated assembler crash on Linux. Clang 3.4 due to compiler
// error with .intel_syntax, http://llvm.org/bugs/show_bug.cgi?id=24232
#if CRYPTOPP_BOOL_X32 || defined(CRYPTOPP_DISABLE_MIXED_ASM)
# define CRYPTOPP_DISABLE_GCM_ASM 1
#endif
 
NAMESPACE_BEGIN(CryptoPP)
 
 
enum GCM_TablesOption {
        GCM_2K_Tables,
        GCM_64K_Tables};
 
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE GCM_Base : public AuthenticatedSymmetricCipherBase
{
public:
        // AuthenticatedSymmetricCipher
        std::string AlgorithmName() const
                {return GetBlockCipher().AlgorithmName() + std::string("/GCM");}
        std::string AlgorithmProvider() const
                {return GetBlockCipher().AlgorithmProvider();}
        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};
};
 
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;
};
 
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