//! truncated version of Verify()
	virtual bool TruncatedVerify(const byte *digest, unsigned int digestLength);

	//! truncated version of VerifyDigest()
	virtual bool VerifyTruncatedDigest(const byte *digest, unsigned int digestLength, const byte *input, unsigned int length)
		{Update(input, length); return TruncatedVerify(digest, digestLength);}

protected:
	void ThrowIfInvalidTruncatedSize(unsigned int size) const;
};

typedef HashTransformation HashFunction;

template <class T>
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE SimpleKeyedTransformation : public T, public SimpleKeyingInterface
{
public:
	void ThrowIfInvalidKeyLength(unsigned int length)
		{SimpleKeyingInterface::ThrowIfInvalidKeyLength(*this, length);}
};

#ifdef CRYPTOPP_DOXYGEN_PROCESSING
//! interface for one direction (encryption or decryption) of a block cipher
/*! \note These objects usually should not be used directly. See BlockTransformation for more details. */
class BlockCipher : public BlockTransformation, public SimpleKeyingInterface {};
//! interface for one direction (encryption or decryption) of a stream cipher or cipher mode
class SymmetricCipher : public StreamTransformation, public SimpleKeyingInterface {};
//! interface for message authentication codes
class MessageAuthenticationCode : public HashTransformation, public SimpleKeyingInterface {};
#else
typedef SimpleKeyedTransformation<BlockTransformation> BlockCipher;
typedef SimpleKeyedTransformation<StreamTransformation> SymmetricCipher;
typedef SimpleKeyedTransformation<HashTransformation> MessageAuthenticationCode;
#endif

CRYPTOPP_DLL_TEMPLATE_CLASS SimpleKeyedTransformation<BlockTransformation>;
CRYPTOPP_DLL_TEMPLATE_CLASS SimpleKeyedTransformation<StreamTransformation>;
CRYPTOPP_DLL_TEMPLATE_CLASS SimpleKeyedTransformation<HashTransformation>;

#ifdef CRYPTOPP_MAINTAIN_BACKWARDS_COMPATIBILITY
typedef SymmetricCipher StreamCipher;
#endif

//! interface for random number generators
/*! All return values are uniformly distributed over the range specified.
*/
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE RandomNumberGenerator : public Algorithm
{
public:
	//! generate new random byte and return it
	virtual byte GenerateByte() =0;

	//! generate new random bit and return it
	/*! Default implementation is to call GenerateByte() and return its parity. */
	virtual unsigned int GenerateBit();

	//! generate a random 32 bit word in the range min to max, inclusive
	virtual word32 GenerateWord32(word32 a=0, word32 b=0xffffffffL);

	//! generate random array of bytes
	/*! Default implementation is to call GenerateByte() size times. */
	virtual void GenerateBlock(byte *output, unsigned int size);

	//! generate and discard n bytes
	/*! Default implementation is to call GenerateByte() n times. */
	virtual void DiscardBytes(unsigned int n);

	//! randomly shuffle the specified array, resulting permutation is uniformly distributed
	template <class IT> void Shuffle(IT begin, IT end)
	{
		for (; begin != end; ++begin)
			std::iter_swap(begin, begin + GenerateWord32(0, end-begin-1));
	}

#ifdef CRYPTOPP_MAINTAIN_BACKWARDS_COMPATIBILITY
	byte GetByte() {return GenerateByte();}
	unsigned int GetBit() {return GenerateBit();}
	word32 GetLong(word32 a=0, word32 b=0xffffffffL) {return GenerateWord32(a, b);}
	word16 GetShort(word16 a=0, word16 b=0xffff) {return (word16)GenerateWord32(a, b);}
	void GetBlock(byte *output, unsigned int size) {GenerateBlock(output, size);}
#endif
};

//! returns a reference that can be passed to functions that ask for a RNG but doesn't actually use it
CRYPTOPP_DLL RandomNumberGenerator & NullRNG();

class WaitObjectContainer;

//! interface for objects that you can wait for

class CRYPTOPP_NO_VTABLE Waitable
{
public:
	//! maximum number of wait objects that this object can return
	virtual unsigned int GetMaxWaitObjectCount() const =0;
	//! put wait objects into container
	virtual void GetWaitObjects(WaitObjectContainer &container) =0;
	//! wait on this object
	/*! same as creating an empty container, calling GetWaitObjects(), and calling Wait() on the container */
	bool Wait(unsigned long milliseconds);
};

//! interface for buffered transformations

/*! BufferedTransformation is a generalization of BlockTransformation,
	StreamTransformation, and HashTransformation.

	A buffered transformation is an object that takes a stream of bytes
	as input (this may be done in stages), does some computation on them, and
	then places the result into an internal buffer for later retrieval.  Any
	partial result already in the output buffer is not modified by further
	input.

	If a method takes a "blocking" parameter, and you
	pass "false" for it, the method will return before all input has been processed if
	the input cannot be processed without waiting (for network buffers to become available, for example).
	In this case the method will return true
	or a non-zero integer value. When this happens you must continue to call the method with the same
	parameters until it returns false or zero, before calling any other method on it or
	attached BufferedTransformation. The integer return value in this case is approximately
	the number of bytes left to be processed, and can be used to implement a progress bar.

	For functions that take a "propagation" parameter, propagation != 0 means pass on the signal to attached
	BufferedTransformation objects, with propagation decremented at each step until it reaches 0.
	-1 means unlimited propagation.

	\nosubgrouping
*/
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE BufferedTransformation : public Algorithm, public Waitable
{
public:
	// placed up here for CW8
	static const std::string NULL_CHANNEL;	// the empty string ""

	BufferedTransformation() : Algorithm(false) {}

	//! return a reference to this object
	/*! This function is useful for passing a temporary BufferedTransformation object to a 
		function that takes a non-const reference. */
	BufferedTransformation& Ref() {return *this;}

	//!	\name INPUT
	//@{
		//! input a byte for processing
		unsigned int Put(byte inByte, bool blocking=true)
			{return Put(&inByte, 1, blocking);}
		//! input multiple bytes
		unsigned int Put(const byte *inString, unsigned int length, bool blocking=true)
			{return Put2(inString, length, 0, blocking);}

		//! input a 16-bit word
		unsigned int PutWord16(word16 value, ByteOrder order=BIG_ENDIAN_ORDER, bool blocking=true);
		//! input a 32-bit word
		unsigned int PutWord32(word32 value, ByteOrder order=BIG_ENDIAN_ORDER, bool blocking=true);

		//! request space which can be written into by the caller, and then used as input to Put()
		/*! \param size is requested size (as a hint) for input, and size of the returned space for output */
		/*! \note The purpose of this method is to help avoid doing extra memory allocations. */
		virtual byte * CreatePutSpace(unsigned int &size) {size=0; return NULL;}

		virtual bool CanModifyInput() const {return false;}

		//! input multiple bytes that may be modified by callee
		unsigned int PutModifiable(byte *inString, unsigned int length, bool blocking=true)
			{return PutModifiable2(inString, length, 0, blocking);}

		bool MessageEnd(int propagation=-1, bool blocking=true)
			{return !!Put2(NULL, 0, propagation < 0 ? -1 : propagation+1, blocking);}
		unsigned int PutMessageEnd(const byte *inString, unsigned int length, int propagation=-1, bool blocking=true)
			{return Put2(inString, length, propagation < 0 ? -1 : propagation+1, blocking);}

		//! input multiple bytes for blocking or non-blocking processing
		/*! \param messageEnd means how many filters to signal MessageEnd to, including this one */
		virtual unsigned int Put2(const byte *inString, unsigned int length, int messageEnd, bool blocking) =0;
		//! input multiple bytes that may be modified by callee for blocking or non-blocking processing
		/*! \param messageEnd means how many filters to signal MessageEnd to, including this one */
		virtual unsigned int PutModifiable2(byte *inString, unsigned int length, int messageEnd, bool blocking)
			{return Put2(inString, length, messageEnd, blocking);}

		//! thrown by objects that have not implemented nonblocking input processing
		struct BlockingInputOnly : public NotImplemented
			{BlockingInputOnly(const std::string &s) : NotImplemented(s + ": Nonblocking input is not implemented by this object.") {}};
	//@}

	//!	\name WAITING
	//@{
		unsigned int GetMaxWaitObjectCount() const;
		void GetWaitObjects(WaitObjectContainer &container);
	//@}

	//!	\name SIGNALS
	//@{
		virtual void IsolatedInitialize(const NameValuePairs &parameters) {throw NotImplemented("BufferedTransformation: this object can't be reinitialized");}
		virtual bool IsolatedFlush(bool hardFlush, bool blocking) =0;
		virtual bool IsolatedMessageSeriesEnd(bool blocking) {return false;}

		//! initialize or reinitialize this object
		virtual void Initialize(const NameValuePairs &parameters=g_nullNameValuePairs, int propagation=-1);
		//! flush buffered input and/or output
		/*! \param hardFlush is used to indicate whether all data should be flushed
			\note Hard flushes must be used with care. It means try to process and output everything, even if
			there may not be enough data to complete the action. For example, hard flushing a HexDecoder would
			cause an error if you do it after inputing an odd number of hex encoded characters.
			For some types of filters, for example ZlibDecompressor, hard flushes can only
			be done at "synchronization points". These synchronization points are positions in the data
			stream that are created by hard flushes on the corresponding reverse filters, in this
			example ZlibCompressor. This is useful when zlib compressed data is moved across a
			network in packets and compression state is preserved across packets, as in the ssh2 protocol.
		*/
		virtual bool Flush(bool hardFlush, int propagation=-1, bool blocking=true);
		//! mark end of a series of messages
		/*! There should be a MessageEnd immediately before MessageSeriesEnd. */
		virtual bool MessageSeriesEnd(int propagation=-1, bool blocking=true);

		//! set propagation of automatically generated and transferred signals
		/*! propagation == 0 means do not automaticly generate signals */
		virtual void SetAutoSignalPropagation(int propagation) {}

		//!
		virtual int GetAutoSignalPropagation() const {return 0;}
public:

#ifdef CRYPTOPP_MAINTAIN_BACKWARDS_COMPATIBILITY
		void Close() {MessageEnd();}
#endif
	//@}

	//!	\name RETRIEVAL OF ONE MESSAGE
	//@{
		//! returns number of bytes that is currently ready for retrieval
		/*! All retrieval functions return the actual number of bytes
			retrieved, which is the lesser of the request number and
			MaxRetrievable(). */
		virtual unsigned long MaxRetrievable() const;

		//! returns whether any bytes are currently ready for retrieval
		virtual bool AnyRetrievable() const;

		//! try to retrieve a single byte
		virtual unsigned int Get(byte &outByte);
		//! try to retrieve multiple bytes
		virtual unsigned int Get(byte *outString, unsigned int getMax);

		//! peek at the next byte without removing it from the output buffer
		virtual unsigned int Peek(byte &outByte) const;
		//! peek at multiple bytes without removing them from the output buffer
		virtual unsigned int Peek(byte *outString, unsigned int peekMax) const;

		//! try to retrieve a 16-bit word
		unsigned int GetWord16(word16 &value, ByteOrder order=BIG_ENDIAN_ORDER);
		//! try to retrieve a 32-bit word
		unsigned int GetWord32(word32 &value, ByteOrder order=BIG_ENDIAN_ORDER);

		//! try to peek at a 16-bit word
		unsigned int PeekWord16(word16 &value, ByteOrder order=BIG_ENDIAN_ORDER);
		//! try to peek at a 32-bit word
		unsigned int PeekWord32(word32 &value, ByteOrder order=BIG_ENDIAN_ORDER);

		//! move transferMax bytes of the buffered output to target as input
		unsigned long TransferTo(BufferedTransformation &target, unsigned long transferMax=ULONG_MAX, const std::string &channel=NULL_CHANNEL)
			{TransferTo2(target, transferMax, channel); return transferMax;}

		//! discard skipMax bytes from the output buffer
		virtual unsigned long Skip(unsigned long skipMax=ULONG_MAX);

		//! copy copyMax bytes of the buffered output to target as input
		unsigned long CopyTo(BufferedTransformation &target, unsigned long copyMax=ULONG_MAX, const std::string &channel=NULL_CHANNEL) const
			{return CopyRangeTo(target, 0, copyMax, channel);}

		//! copy copyMax bytes of the buffered output, starting at position (relative to current position), to target as input
		unsigned long CopyRangeTo(BufferedTransformation &target, unsigned long position, unsigned long copyMax=ULONG_MAX, const std::string &channel=NULL_CHANNEL) const
			{unsigned long i = position; CopyRangeTo2(target, i, i+copyMax, channel); return i-position;}

#ifdef CRYPTOPP_MAINTAIN_BACKWARDS_COMPATIBILITY
		unsigned long MaxRetrieveable() const {return MaxRetrievable();}
#endif
	//@}

	//!	\name RETRIEVAL OF MULTIPLE MESSAGES
	//@{
		//!
		virtual unsigned long TotalBytesRetrievable() const;
		//! number of times MessageEnd() has been received minus messages retrieved or skipped
		virtual unsigned int NumberOfMessages() const;