source: git/src-cryptopp/strciphr.h

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

//! \file strciphr.h
//! \brief Classes for implementing stream ciphers
//! \details This file contains helper classes for implementing stream ciphers.
//!   All this infrastructure may look very complex compared to what's in Crypto++ 4.x,
//!   but stream ciphers implementations now support a lot of new functionality,
//!   including better performance (minimizing copying), resetting of keys and IVs, and methods to
//!   query which features are supported by a cipher.
//! \details Here's an explanation of these classes. The word "policy" is used here to mean a class with a
//!   set of methods that must be implemented by individual stream cipher implementations.
//!   This is usually much simpler than the full stream cipher API, which is implemented by
//!   either AdditiveCipherTemplate or CFB_CipherTemplate using the policy. So for example, an
//!   implementation of SEAL only needs to implement the AdditiveCipherAbstractPolicy interface
//!   (since it's an additive cipher, i.e., it xors a keystream into the plaintext).
//!   See this line in seal.h:
//! <pre>
//!     typedef SymmetricCipherFinal\<ConcretePolicyHolder\<SEAL_Policy\<B\>, AdditiveCipherTemplate\<\> \> \> Encryption;
//! </pre>
//! \details AdditiveCipherTemplate and CFB_CipherTemplate are designed so that they don't need
//!   to take a policy class as a template parameter (although this is allowed), so that
//!   their code is not duplicated for each new cipher. Instead they each
//!   get a reference to an abstract policy interface by calling AccessPolicy() on itself, so
//!   AccessPolicy() must be overriden to return the actual policy reference. This is done
//!   by the ConceretePolicyHolder class. Finally, SymmetricCipherFinal implements the constructors and
//!   other functions that must be implemented by the most derived class.

#ifndef CRYPTOPP_STRCIPHR_H
#define CRYPTOPP_STRCIPHR_H

#include "config.h"

#if CRYPTOPP_MSC_VERSION
# pragma warning(push)
# pragma warning(disable: 4127 4189)
#endif

#include "cryptlib.h"
#include "seckey.h"
#include "secblock.h"
#include "argnames.h"

NAMESPACE_BEGIN(CryptoPP)

//! \class AbstractPolicyHolder
//! \brief Access a stream cipher policy object
//! \tparam POLICY_INTERFACE class implementing AbstractPolicyHolder
//! \tparam BASE class or type to use as a base class
template <class POLICY_INTERFACE, class BASE = Empty>
class CRYPTOPP_NO_VTABLE AbstractPolicyHolder : public BASE
{
public:
        typedef POLICY_INTERFACE PolicyInterface;
        virtual ~AbstractPolicyHolder() {}

protected:
        virtual const POLICY_INTERFACE & GetPolicy() const =0;
        virtual POLICY_INTERFACE & AccessPolicy() =0;
};

//! \class ConcretePolicyHolder
//! \brief Stream cipher policy object
//! \tparam POLICY class implementing AbstractPolicyHolder
//! \tparam BASE class or type to use as a base class
template <class POLICY, class BASE, class POLICY_INTERFACE = CPP_TYPENAME BASE::PolicyInterface>
class ConcretePolicyHolder : public BASE, protected POLICY
{
public:
#ifndef CRYPTOPP_MAINTAIN_BACKWARDS_COMPATIBILITY_562
        virtual ~ConcretePolicyHolder() {}
#endif
protected:
        const POLICY_INTERFACE & GetPolicy() const {return *this;}
        POLICY_INTERFACE & AccessPolicy() {return *this;}
};

//! \brief Keystream operation flags
//! \sa AdditiveCipherAbstractPolicy::GetBytesPerIteration(), AdditiveCipherAbstractPolicy::GetOptimalBlockSize()
//!   and AdditiveCipherAbstractPolicy::GetAlignment()
enum KeystreamOperationFlags {
        //! \brief Output buffer is aligned
        OUTPUT_ALIGNED=1,
        //! \brief Input buffer is aligned
        INPUT_ALIGNED=2,
        //! \brief Input buffer is NULL
        INPUT_NULL = 4
};

//! \brief Keystream operation flags
//! \sa AdditiveCipherAbstractPolicy::GetBytesPerIteration(), AdditiveCipherAbstractPolicy::GetOptimalBlockSize()
//!   and AdditiveCipherAbstractPolicy::GetAlignment()
enum KeystreamOperation {
        //! \brief Wirte the keystream to the output buffer, input is NULL
        WRITE_KEYSTREAM                         = INPUT_NULL,
        //! \brief Wirte the keystream to the aligned output buffer, input is NULL
        WRITE_KEYSTREAM_ALIGNED         = INPUT_NULL | OUTPUT_ALIGNED,
        //! \brief XOR the input buffer and keystream, write to the output buffer
        XOR_KEYSTREAM                           = 0,
        //! \brief XOR the aligned input buffer and keystream, write to the output buffer
        XOR_KEYSTREAM_INPUT_ALIGNED = INPUT_ALIGNED,
        //! \brief XOR the input buffer and keystream, write to the aligned output buffer
        XOR_KEYSTREAM_OUTPUT_ALIGNED= OUTPUT_ALIGNED,
        //! \brief XOR the aligned input buffer and keystream, write to the aligned output buffer
        XOR_KEYSTREAM_BOTH_ALIGNED      = OUTPUT_ALIGNED | INPUT_ALIGNED};

//! \class AdditiveCipherAbstractPolicy
//! \brief Policy object for additive stream ciphers
struct CRYPTOPP_DLL CRYPTOPP_NO_VTABLE AdditiveCipherAbstractPolicy
{
        virtual ~AdditiveCipherAbstractPolicy() {}

        //! \brief Provides data alignment requirements
        //! \returns data alignment requirements, in bytes
        //! \details Internally, the default implementation returns 1. If the stream cipher is implemented
        //!   using an SSE2 ASM or intrinsics, then the value returned is usually 16.
        virtual unsigned int GetAlignment() const {return 1;}

        //! \brief Provides number of bytes operated upon during an iteration
        //! \returns bytes operated upon during an iteration, in bytes
        //! \sa GetOptimalBlockSize()
        virtual unsigned int GetBytesPerIteration() const =0;

        //! \brief Provides number of ideal bytes to process
        //! \returns the ideal number of bytes to process
        //! \details Internally, the default implementation returns GetBytesPerIteration()
        //! \sa GetBytesPerIteration()
        virtual unsigned int GetOptimalBlockSize() const {return GetBytesPerIteration();}

        //! \brief Provides buffer size based on iterations
        //! \returns the buffer size based on iterations, in bytes
        virtual unsigned int GetIterationsToBuffer() const =0;

        //! \brief Generate the keystream
        //! \param keystream the key stream
        //! \param iterationCount the number of iterations to generate the key stream
        //! \sa CanOperateKeystream(), OperateKeystream(), WriteKeystream()
        virtual void WriteKeystream(byte *keystream, size_t iterationCount)
                {OperateKeystream(KeystreamOperation(INPUT_NULL | (KeystreamOperationFlags)IsAlignedOn(keystream, GetAlignment())), keystream, NULL, iterationCount);}

        //! \brief Flag indicating
        //! \returns true if the stream can be generated independent of the transformation input, false otherwise
        //! \sa CanOperateKeystream(), OperateKeystream(), WriteKeystream()
        virtual bool CanOperateKeystream() const {return false;}

        //! \brief Operates the keystream
        //! \param operation the operation with additional flags
        //! \param output the output buffer
        //! \param input the input buffer
        //! \param iterationCount the number of iterations to perform on the input
        //! \details OperateKeystream() will attempt to operate upon GetOptimalBlockSize() buffer,
        //!   which will be derived from GetBytesPerIteration().
        //! \sa CanOperateKeystream(), OperateKeystream(), WriteKeystream(), KeystreamOperation()
        virtual void OperateKeystream(KeystreamOperation operation, byte *output, const byte *input, size_t iterationCount)
                {CRYPTOPP_UNUSED(operation); CRYPTOPP_UNUSED(output); CRYPTOPP_UNUSED(input); CRYPTOPP_UNUSED(iterationCount); CRYPTOPP_ASSERT(false);}

        //! \brief Key the cipher
        //! \param params set of NameValuePairs use to initialize this object
        //! \param key a byte array used to key the cipher
        //! \param length the size of the key array
        virtual void CipherSetKey(const NameValuePairs &params, const byte *key, size_t length) =0;

        //! \brief Resynchronize the cipher
        //! \param keystreamBuffer the keystream buffer
        //! \param iv a byte array used to resynchronize the cipher
        //! \param length the size of the IV array
        virtual void CipherResynchronize(byte *keystreamBuffer, const byte *iv, size_t length)
                {CRYPTOPP_UNUSED(keystreamBuffer); CRYPTOPP_UNUSED(iv); CRYPTOPP_UNUSED(length); throw NotImplemented("SimpleKeyingInterface: this object doesn't support resynchronization");}

        //! \brief Flag indicating random access
        //! \returns true if the cipher is seekable, false otherwise
        //! \sa SeekToIteration()
        virtual bool CipherIsRandomAccess() const =0;

        //! \brief Seeks to a random position in the stream
        //! \returns iterationCount
        //! \sa CipherIsRandomAccess()
        virtual void SeekToIteration(lword iterationCount)
                {CRYPTOPP_UNUSED(iterationCount); CRYPTOPP_ASSERT(!CipherIsRandomAccess()); throw NotImplemented("StreamTransformation: this object doesn't support random access");}
};

//! \class AdditiveCipherConcretePolicy
//! \brief Base class for additive stream ciphers
//! \tparam WT word type
//! \tparam W count of words
//! \tparam X bytes per iteration count
//! \tparam BASE AdditiveCipherAbstractPolicy derived base class
template <typename WT, unsigned int W, unsigned int X = 1, class BASE = AdditiveCipherAbstractPolicy>
struct CRYPTOPP_NO_VTABLE AdditiveCipherConcretePolicy : public BASE
{
        typedef WT WordType;
        CRYPTOPP_CONSTANT(BYTES_PER_ITERATION = sizeof(WordType) * W)

#if !(CRYPTOPP_BOOL_X86 || CRYPTOPP_BOOL_X64)
        //! \brief Provides data alignment requirements
        //! \returns data alignment requirements, in bytes
        //! \details Internally, the default implementation returns 1. If the stream cipher is implemented
        //!   using an SSE2 ASM or intrinsics, then the value returned is usually 16.
        unsigned int GetAlignment() const {return GetAlignmentOf<WordType>();}
#endif

        //! \brief Provides number of bytes operated upon during an iteration
        //! \returns bytes operated upon during an iteration, in bytes
        //! \sa GetOptimalBlockSize()
        unsigned int GetBytesPerIteration() const {return BYTES_PER_ITERATION;}

        //! \brief Provides buffer size based on iterations
        //! \returns the buffer size based on iterations, in bytes
        unsigned int GetIterationsToBuffer() const {return X;}

        //! \brief Flag indicating
        //! \returns true if the stream can be generated independent of the transformation input, false otherwise
        //! \sa CanOperateKeystream(), OperateKeystream(), WriteKeystream()
        bool CanOperateKeystream() const {return true;}

        //! \brief Operates the keystream
        //! \param operation the operation with additional flags
        //! \param output the output buffer
        //! \param input the input buffer
        //! \param iterationCount the number of iterations to perform on the input
        //! \details OperateKeystream() will attempt to operate upon GetOptimalBlockSize() buffer,
        //!   which will be derived from GetBytesPerIteration().
        //! \sa CanOperateKeystream(), OperateKeystream(), WriteKeystream(), KeystreamOperation()
        virtual void OperateKeystream(KeystreamOperation operation, byte *output, const byte *input, size_t iterationCount) =0;
};

//! \brief Helper macro to implement OperateKeystream
#define CRYPTOPP_KEYSTREAM_OUTPUT_WORD(x, b, i, a)      \
        PutWord(bool(x & OUTPUT_ALIGNED), b, output+i*sizeof(WordType), (x & INPUT_NULL) ? (a) : (a) ^ GetWord<WordType>(bool(x & INPUT_ALIGNED), b, input+i*sizeof(WordType)));

//! \brief Helper macro to implement OperateKeystream
#define CRYPTOPP_KEYSTREAM_OUTPUT_XMM(x, i, a)  {\
        __m128i t = (x & INPUT_NULL) ? a : _mm_xor_si128(a, (x & INPUT_ALIGNED) ? _mm_load_si128((__m128i *)input+i) : _mm_loadu_si128((__m128i *)input+i));\
        if (x & OUTPUT_ALIGNED) _mm_store_si128((__m128i *)output+i, t);\
        else _mm_storeu_si128((__m128i *)output+i, t);}

//! \brief Helper macro to implement OperateKeystream
#define CRYPTOPP_KEYSTREAM_OUTPUT_SWITCH(x, y)  \
        switch (operation)                                                      \
        {                                                                                       \
                case WRITE_KEYSTREAM:                                   \
                        x(WRITE_KEYSTREAM)                                      \
                        break;                                                          \
                case XOR_KEYSTREAM:                                             \
                        x(XOR_KEYSTREAM)                                        \
                        input += y;                                                     \
                        break;                                                          \
                case XOR_KEYSTREAM_INPUT_ALIGNED:               \
                        x(XOR_KEYSTREAM_INPUT_ALIGNED)          \
                        input += y;                                                     \
                        break;                                                          \
                case XOR_KEYSTREAM_OUTPUT_ALIGNED:              \
                        x(XOR_KEYSTREAM_OUTPUT_ALIGNED)         \
                        input += y;                                                     \
                        break;                                                          \
                case WRITE_KEYSTREAM_ALIGNED:                   \
                        x(WRITE_KEYSTREAM_ALIGNED)                      \
                        break;                                                          \
                case XOR_KEYSTREAM_BOTH_ALIGNED:                \
                        x(XOR_KEYSTREAM_BOTH_ALIGNED)           \
                        input += y;                                                     \
                        break;                                                          \
        }                                                                                       \
        output += y;

//! \class AdditiveCipherTemplate
//! \brief Base class for additive stream ciphers with SymmetricCipher interface
//! \tparam BASE AbstractPolicyHolder base class
template <class BASE = AbstractPolicyHolder<AdditiveCipherAbstractPolicy, SymmetricCipher> >
class CRYPTOPP_NO_VTABLE AdditiveCipherTemplate : public BASE, public RandomNumberGenerator
{
public:
        //! \brief Generate random array of bytes
        //! \param output the byte buffer
        //! \param size the length of the buffer, in bytes
        //! \details All generated values are uniformly distributed over the range specified within the
        //!   the contraints of a particular generator.
        void GenerateBlock(byte *output, size_t size);

        //! \brief Apply keystream to data
        //! \param outString a buffer to write the transformed data
        //! \param inString a buffer to read the data
        //! \param length the size fo the buffers, in bytes
        //! \details This is the primary method to operate a stream cipher. For example:
        //! <pre>
        //!     size_t size = 30;
        //!     byte plain[size] = "Do or do not; there is no try";
        //!     byte cipher[size];
        //!     ...
        //!     ChaCha20 chacha(key, keySize);
        //!     chacha.ProcessData(cipher, plain, size);
        //! </pre>
    void ProcessData(byte *outString, const byte *inString, size_t length);

        //! \brief Resynchronize the cipher
        //! \param iv a byte array used to resynchronize the cipher
        //! \param length the size of the IV array
        void Resynchronize(const byte *iv, int length=-1);

        //! \brief Provides number of ideal bytes to process
        //! \returns the ideal number of bytes to process
        //! \details Internally, the default implementation returns GetBytesPerIteration()
        //! \sa GetBytesPerIteration() and GetOptimalNextBlockSize()
        unsigned int OptimalBlockSize() const {return this->GetPolicy().GetOptimalBlockSize();}

        //! \brief Provides number of ideal bytes to process
        //! \returns the ideal number of bytes to process
        //! \details Internally, the default implementation returns remaining unprocessed bytes
        //! \sa GetBytesPerIteration() and OptimalBlockSize()
        unsigned int GetOptimalNextBlockSize() const {return (unsigned int)this->m_leftOver;}

        //! \brief Provides number of ideal data alignment
        //! \returns the ideal data alignment, in bytes
        //! \sa GetAlignment() and OptimalBlockSize()
        unsigned int OptimalDataAlignment() const {return this->GetPolicy().GetAlignment();}

        //! \brief Determines if the cipher is self inverting
        //! \returns true if the stream cipher is self inverting, false otherwise
        bool IsSelfInverting() const {return true;}

        //! \brief Determines if the cipher is a forward transformation
        //! \returns true if the stream cipher is a forward transformation, false otherwise
        bool IsForwardTransformation() const {return true;}

        //! \brief Flag indicating random access
        //! \returns true if the cipher is seekable, false otherwise
        //! \sa Seek()
        bool IsRandomAccess() const {return this->GetPolicy().CipherIsRandomAccess();}

        //! \brief Seeks to a random position in the stream
        //! \param position the absolute position in the stream
        //! \sa IsRandomAccess()
        void Seek(lword position);

        typedef typename BASE::PolicyInterface PolicyInterface;

protected:
        void UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params);

        unsigned int GetBufferByteSize(const PolicyInterface &policy) const {return policy.GetBytesPerIteration() * policy.GetIterationsToBuffer();}

        inline byte * KeystreamBufferBegin() {return this->m_buffer.data();}
        inline byte * KeystreamBufferEnd() {return (this->m_buffer.data() + this->m_buffer.size());}

        SecByteBlock m_buffer;
        size_t m_leftOver;
};

//! \class CFB_CipherAbstractPolicy
//! \brief Policy object for feeback based stream ciphers
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE CFB_CipherAbstractPolicy
{
public:
        virtual ~CFB_CipherAbstractPolicy() {}

        //! \brief Provides data alignment requirements
        //! \returns data alignment requirements, in bytes
        //! \details Internally, the default implementation returns 1. If the stream cipher is implemented
        //!   using an SSE2 ASM or intrinsics, then the value returned is usually 16.
        virtual unsigned int GetAlignment() const =0;

        //! \brief Provides number of bytes operated upon during an iteration
        //! \returns bytes operated upon during an iteration, in bytes
        //! \sa GetOptimalBlockSize()
        virtual unsigned int GetBytesPerIteration() const =0;

        //! \brief Access the feedback register
        //! \returns pointer to the first byte of the feedback register
        virtual byte * GetRegisterBegin() =0;

        //! \brief TODO
        virtual void TransformRegister() =0;

        //! \brief Flag indicating iteration support
        //! \returns true if the cipher supports iteration, false otherwise
        virtual bool CanIterate() const {return false;}

        //! \brief Iterate the cipher
        //! \param output the output buffer
        //! \param input the input buffer
        //! \param dir the direction of the cipher
        //! \param iterationCount the number of iterations to perform on the input
        //! \sa IsSelfInverting() and IsForwardTransformation()
        virtual void Iterate(byte *output, const byte *input, CipherDir dir, size_t iterationCount)
                {CRYPTOPP_UNUSED(output); CRYPTOPP_UNUSED(input); CRYPTOPP_UNUSED(dir); CRYPTOPP_UNUSED(iterationCount);
                 CRYPTOPP_ASSERT(false); /*throw 0;*/ throw Exception(Exception::OTHER_ERROR, "SimpleKeyingInterface: unexpected error");}

        //! \brief Key the cipher
        //! \param params set of NameValuePairs use to initialize this object
        //! \param key a byte array used to key the cipher
        //! \param length the size of the key array
        virtual void CipherSetKey(const NameValuePairs &params, const byte *key, size_t length) =0;

        //! \brief Resynchronize the cipher
        //! \param iv a byte array used to resynchronize the cipher
        //! \param length the size of the IV array
        virtual void CipherResynchronize(const byte *iv, size_t length)
                {CRYPTOPP_UNUSED(iv); CRYPTOPP_UNUSED(length); throw NotImplemented("SimpleKeyingInterface: this object doesn't support resynchronization");}
};

//! \class CFB_CipherConcretePolicy
//! \brief Base class for feedback based stream ciphers
//! \tparam WT word type
//! \tparam W count of words
//! \tparam BASE CFB_CipherAbstractPolicy derived base class
template <typename WT, unsigned int W, class BASE = CFB_CipherAbstractPolicy>
struct CRYPTOPP_NO_VTABLE CFB_CipherConcretePolicy : public BASE
{
        typedef WT WordType;

        //! \brief Provides data alignment requirements
        //! \returns data alignment requirements, in bytes
        //! \details Internally, the default implementation returns 1. If the stream cipher is implemented
        //!   using an SSE2 ASM or intrinsics, then the value returned is usually 16.
        unsigned int GetAlignment() const {return sizeof(WordType);}

        //! \brief Provides number of bytes operated upon during an iteration
        //! \returns bytes operated upon during an iteration, in bytes
        //! \sa GetOptimalBlockSize()
        unsigned int GetBytesPerIteration() const {return sizeof(WordType) * W;}

        //! \brief Flag indicating iteration support
        //! \returns true if the cipher supports iteration, false otherwise
        bool CanIterate() const {return true;}

        //! \brief Perform one iteration in the forward direction
        void TransformRegister() {this->Iterate(NULL, NULL, ENCRYPTION, 1);}

        //! \brief
        //! \tparam B enumeration indicating endianess
        //! \details RegisterOutput() provides alternate access to the feedback register. The
        //!   enumeration B is BigEndian or LittleEndian. Repeatedly applying operator()
        //!   results in advancing in the register.
        template <class B>
        struct RegisterOutput
        {
                RegisterOutput(byte *output, const byte *input, CipherDir dir)
                        : m_output(output), m_input(input), m_dir(dir) {}

                //! \brief XOR feedback register with data
                //! \param registerWord data represented as a word type
                //! \returns reference to the next feedback register word
                inline RegisterOutput& operator()(WordType &registerWord)
                {
                        CRYPTOPP_ASSERT(IsAligned<WordType>(m_output));
                        CRYPTOPP_ASSERT(IsAligned<WordType>(m_input));

                        if (!NativeByteOrderIs(B::ToEnum()))
                                registerWord = ByteReverse(registerWord);

                        if (m_dir == ENCRYPTION)
                        {
                                if (m_input == NULL)
                                {
                                        CRYPTOPP_ASSERT(m_output == NULL);
                                }
                                else
                                {
                                        WordType ct = *(const WordType *)m_input ^ registerWord;
                                        registerWord = ct;
                                        *(WordType*)m_output = ct;
                                        m_input += sizeof(WordType);
                                        m_output += sizeof(WordType);
                                }
                        }
                        else
                        {
                                WordType ct = *(const WordType *)m_input;
                                *(WordType*)m_output = registerWord ^ ct;
                                registerWord = ct;
                                m_input += sizeof(WordType);
                                m_output += sizeof(WordType);
                        }

                        // registerWord is left unreversed so it can be xor-ed with further input

                        return *this;
                }

                byte *m_output;
                const byte *m_input;
                CipherDir m_dir;
        };
};

//! \class CFB_CipherTemplate
//! \brief Base class for feedback based stream ciphers with SymmetricCipher interface
//! \tparam BASE AbstractPolicyHolder base class
template <class BASE>
class CRYPTOPP_NO_VTABLE CFB_CipherTemplate : public BASE
{
public:
        //! \brief Apply keystream to data
        //! \param outString a buffer to write the transformed data
        //! \param inString a buffer to read the data
        //! \param length the size fo the buffers, in bytes
        //! \details This is the primary method to operate a stream cipher. For example:
        //! <pre>
        //!     size_t size = 30;
        //!     byte plain[size] = "Do or do not; there is no try";
        //!     byte cipher[size];
        //!     ...
        //!     ChaCha20 chacha(key, keySize);
        //!     chacha.ProcessData(cipher, plain, size);
        //! </pre>
        void ProcessData(byte *outString, const byte *inString, size_t length);

        //! \brief Resynchronize the cipher
        //! \param iv a byte array used to resynchronize the cipher
        //! \param length the size of the IV array
        void Resynchronize(const byte *iv, int length=-1);

        //! \brief Provides number of ideal bytes to process
        //! \returns the ideal number of bytes to process
        //! \details Internally, the default implementation returns GetBytesPerIteration()
        //! \sa GetBytesPerIteration() and GetOptimalNextBlockSize()
        unsigned int OptimalBlockSize() const {return this->GetPolicy().GetBytesPerIteration();}

        //! \brief Provides number of ideal bytes to process
        //! \returns the ideal number of bytes to process
        //! \details Internally, the default implementation returns remaining unprocessed bytes
        //! \sa GetBytesPerIteration() and OptimalBlockSize()
        unsigned int GetOptimalNextBlockSize() const {return (unsigned int)m_leftOver;}

        //! \brief Provides number of ideal data alignment
        //! \returns the ideal data alignment, in bytes
        //! \sa GetAlignment() and OptimalBlockSize()
        unsigned int OptimalDataAlignment() const {return this->GetPolicy().GetAlignment();}

        //! \brief Flag indicating random access
        //! \returns true if the cipher is seekable, false otherwise
        //! \sa Seek()
        bool IsRandomAccess() const {return false;}

        //! \brief Determines if the cipher is self inverting
        //! \returns true if the stream cipher is self inverting, false otherwise
        bool IsSelfInverting() const {return false;}

        typedef typename BASE::PolicyInterface PolicyInterface;

protected:
        virtual void CombineMessageAndShiftRegister(byte *output, byte *reg, const byte *message, size_t length) =0;

        void UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params);

        size_t m_leftOver;
};

//! \class CFB_EncryptionTemplate
//! \brief Base class for feedback based stream ciphers in the forward direction with SymmetricCipher interface
//! \tparam BASE AbstractPolicyHolder base class
template <class BASE = AbstractPolicyHolder<CFB_CipherAbstractPolicy, SymmetricCipher> >
class CRYPTOPP_NO_VTABLE CFB_EncryptionTemplate : public CFB_CipherTemplate<BASE>
{
        bool IsForwardTransformation() const {return true;}
        void CombineMessageAndShiftRegister(byte *output, byte *reg, const byte *message, size_t length);
};

//! \class CFB_DecryptionTemplate
//! \brief Base class for feedback based stream ciphers in the reverse direction with SymmetricCipher interface
//! \tparam BASE AbstractPolicyHolder base class
template <class BASE = AbstractPolicyHolder<CFB_CipherAbstractPolicy, SymmetricCipher> >
class CRYPTOPP_NO_VTABLE CFB_DecryptionTemplate : public CFB_CipherTemplate<BASE>
{
        bool IsForwardTransformation() const {return false;}
        void CombineMessageAndShiftRegister(byte *output, byte *reg, const byte *message, size_t length);
};

//! \class CFB_RequireFullDataBlocks
//! \brief Base class for feedback based stream ciphers with a mandatory block size
//! \tparam BASE CFB_EncryptionTemplate or CFB_DecryptionTemplate base class
template <class BASE>
class CFB_RequireFullDataBlocks : public BASE
{
public:
        unsigned int MandatoryBlockSize() const {return this->OptimalBlockSize();}
};

//! \class SymmetricCipherFinal
//! \brief SymmetricCipher implementation
//! \tparam BASE AbstractPolicyHolder derived base class
//! \tparam INFO AbstractPolicyHolder derived information class
//! \sa Weak::ARC4, ChaCha8, ChaCha12, ChaCha20, Salsa20, SEAL, Sosemanuk, WAKE
template <class BASE, class INFO = BASE>
class SymmetricCipherFinal : public AlgorithmImpl<SimpleKeyingInterfaceImpl<BASE, INFO>, INFO>
{
public:
        //! \brief Construct a stream cipher
        SymmetricCipherFinal() {}

        //! \brief Construct a stream cipher
        //! \param key a byte array used to key the cipher
        //! \details This overload uses DEFAULT_KEYLENGTH
        SymmetricCipherFinal(const byte *key)
                {this->SetKey(key, this->DEFAULT_KEYLENGTH);}

        //! \brief Construct a stream cipher
        //! \param key a byte array used to key the cipher
        //! \param length the size of the key array
        SymmetricCipherFinal(const byte *key, size_t length)
                {this->SetKey(key, length);}

        //! \brief Construct a stream cipher
        //! \param key a byte array used to key the cipher
        //! \param length the size of the key array
        //! \param iv a byte array used as an initialization vector
        SymmetricCipherFinal(const byte *key, size_t length, const byte *iv)
                {this->SetKeyWithIV(key, length, iv);}

        //! \brief Clone a SymmetricCipher
        //! \returns a new SymmetricCipher based on this object
        Clonable * Clone() const {return static_cast<SymmetricCipher *>(new SymmetricCipherFinal<BASE, INFO>(*this));}
};

NAMESPACE_END

#ifdef CRYPTOPP_MANUALLY_INSTANTIATE_TEMPLATES
#include "strciphr.cpp"
#endif

NAMESPACE_BEGIN(CryptoPP)
CRYPTOPP_DLL_TEMPLATE_CLASS AbstractPolicyHolder<AdditiveCipherAbstractPolicy, SymmetricCipher>;
CRYPTOPP_DLL_TEMPLATE_CLASS AdditiveCipherTemplate<AbstractPolicyHolder<AdditiveCipherAbstractPolicy, SymmetricCipher> >;
CRYPTOPP_DLL_TEMPLATE_CLASS CFB_CipherTemplate<AbstractPolicyHolder<CFB_CipherAbstractPolicy, SymmetricCipher> >;
CRYPTOPP_DLL_TEMPLATE_CLASS CFB_EncryptionTemplate<AbstractPolicyHolder<CFB_CipherAbstractPolicy, SymmetricCipher> >;
CRYPTOPP_DLL_TEMPLATE_CLASS CFB_DecryptionTemplate<AbstractPolicyHolder<CFB_CipherAbstractPolicy, SymmetricCipher> >;

NAMESPACE_END

#if CRYPTOPP_MSC_VERSION
# pragma warning(pop)
#endif

#endif