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[novacoin.git] / cryptopp / cryptlib.h

// cryptlib.h - written and placed in the public domain by Wei Dai
/*! \file
        This file contains the declarations for the abstract base
        classes that provide a uniform interface to this library.
*/

/*!     \mainpage Crypto++ Library 5.6.0 API Reference
<dl>
<dt>Abstract Base Classes<dd>
        cryptlib.h
<dt>Authenticated Encryption<dd>
        AuthenticatedSymmetricCipherDocumentation
<dt>Symmetric Ciphers<dd>
        SymmetricCipherDocumentation
<dt>Hash Functions<dd>
        SHA1, SHA224, SHA256, SHA384, SHA512, Tiger, Whirlpool, RIPEMD160, RIPEMD320, RIPEMD128, RIPEMD256, Weak1::MD2, Weak1::MD4, Weak1::MD5
<dt>Non-Cryptographic Checksums<dd>
        CRC32, Adler32
<dt>Message Authentication Codes<dd>
        VMAC, HMAC, CBC_MAC, CMAC, DMAC, TTMAC, GCM (GMAC)
<dt>Random Number Generators<dd>
        NullRNG(), LC_RNG, RandomPool, BlockingRng, NonblockingRng, AutoSeededRandomPool, AutoSeededX917RNG, DefaultAutoSeededRNG
<dt>Password-based Cryptography<dd>
        PasswordBasedKeyDerivationFunction
<dt>Public Key Cryptosystems<dd>
        DLIES, ECIES, LUCES, RSAES, RabinES, LUC_IES
<dt>Public Key Signature Schemes<dd>
        DSA, GDSA, ECDSA, NR, ECNR, LUCSS, RSASS, RSASS_ISO, RabinSS, RWSS, ESIGN
<dt>Key Agreement<dd>
        #DH, DH2, #MQV, ECDH, ECMQV, XTR_DH
<dt>Algebraic Structures<dd>
        Integer, PolynomialMod2, PolynomialOver, RingOfPolynomialsOver,
        ModularArithmetic, MontgomeryRepresentation, GFP2_ONB,
        GF2NP, GF256, GF2_32, EC2N, ECP
<dt>Secret Sharing and Information Dispersal<dd>
        SecretSharing, SecretRecovery, InformationDispersal, InformationRecovery
<dt>Compression<dd>
        Deflator, Inflator, Gzip, Gunzip, ZlibCompressor, ZlibDecompressor
<dt>Input Source Classes<dd>
        StringSource, ArraySource, FileSource, SocketSource, WindowsPipeSource, RandomNumberSource
<dt>Output Sink Classes<dd>
        StringSinkTemplate, ArraySink, FileSink, SocketSink, WindowsPipeSink, RandomNumberSink
<dt>Filter Wrappers<dd>
        StreamTransformationFilter, HashFilter, HashVerificationFilter, SignerFilter, SignatureVerificationFilter
<dt>Binary to Text Encoders and Decoders<dd>
        HexEncoder, HexDecoder, Base64Encoder, Base64Decoder, Base32Encoder, Base32Decoder
<dt>Wrappers for OS features<dd>
        Timer, Socket, WindowsHandle, ThreadLocalStorage, ThreadUserTimer
<dt>FIPS 140 related<dd>
        fips140.h
</dl>

In the FIPS 140-2 validated DLL version of Crypto++, only the following implementation class are available.
<dl>
<dt>Block Ciphers<dd>
        AES, DES_EDE2, DES_EDE3, SKIPJACK
<dt>Cipher Modes (replace template parameter BC with one of the block ciphers above)<dd>
        ECB_Mode\<BC\>, CTR_Mode\<BC\>, CBC_Mode\<BC\>, CFB_FIPS_Mode\<BC\>, OFB_Mode\<BC\>
<dt>Hash Functions<dd>
        SHA1, SHA224, SHA256, SHA384, SHA512
<dt>Public Key Signature Schemes (replace template parameter H with one of the hash functions above)<dd>
        RSASS\<PKCS1v15, H\>, RSASS\<PSS, H\>, RSASS_ISO\<H\>, RWSS\<P1363_EMSA2, H\>, DSA, ECDSA\<ECP, H\>, ECDSA\<EC2N, H\>
<dt>Message Authentication Codes (replace template parameter H with one of the hash functions above)<dd>
        HMAC\<H\>, CBC_MAC\<DES_EDE2\>, CBC_MAC\<DES_EDE3\>
<dt>Random Number Generators<dd>
        DefaultAutoSeededRNG (AutoSeededX917RNG\<AES\>)
<dt>Key Agreement<dd>
        #DH
<dt>Public Key Cryptosystems<dd>
        RSAES\<OAEP\<SHA1\> \>
</dl>

<p>This reference manual is a work in progress. Some classes are still lacking detailed descriptions.
<p>Click <a href="CryptoPPRef.zip">here</a> to download a zip archive containing this manual.
<p>Thanks to Ryan Phillips for providing the Doxygen configuration file
and getting me started with this manual.
*/

#ifndef CRYPTOPP_CRYPTLIB_H
#define CRYPTOPP_CRYPTLIB_H

#include "config.h"
#include "stdcpp.h"

NAMESPACE_BEGIN(CryptoPP)

// forward declarations
class Integer;
class RandomNumberGenerator;
class BufferedTransformation;

//! used to specify a direction for a cipher to operate in (encrypt or decrypt)
enum CipherDir {ENCRYPTION, DECRYPTION};

//! used to represent infinite time
const unsigned long INFINITE_TIME = ULONG_MAX;

// VC60 workaround: using enums as template parameters causes problems
template <typename ENUM_TYPE, int VALUE>
struct EnumToType
{
        static ENUM_TYPE ToEnum() {return (ENUM_TYPE)VALUE;}
};

enum ByteOrder {LITTLE_ENDIAN_ORDER = 0, BIG_ENDIAN_ORDER = 1};
typedef EnumToType<ByteOrder, LITTLE_ENDIAN_ORDER> LittleEndian;
typedef EnumToType<ByteOrder, BIG_ENDIAN_ORDER> BigEndian;

//! base class for all exceptions thrown by Crypto++
class CRYPTOPP_DLL Exception : public std::exception
{
public:
        //! error types
        enum ErrorType {
                //! a method is not implemented
                NOT_IMPLEMENTED,
                //! invalid function argument
                INVALID_ARGUMENT,
                //! BufferedTransformation received a Flush(true) signal but can't flush buffers
                CANNOT_FLUSH,
                //! data integerity check (such as CRC or MAC) failed
                DATA_INTEGRITY_CHECK_FAILED,
                //! received input data that doesn't conform to expected format
                INVALID_DATA_FORMAT,
                //! error reading from input device or writing to output device
                IO_ERROR,
                //! some error not belong to any of the above categories
                OTHER_ERROR
        };

        explicit Exception(ErrorType errorType, const std::string &s) : m_errorType(errorType), m_what(s) {}
        virtual ~Exception() throw() {}
        const char *what() const throw() {return (m_what.c_str());}
        const std::string &GetWhat() const {return m_what;}
        void SetWhat(const std::string &s) {m_what = s;}
        ErrorType GetErrorType() const {return m_errorType;}
        void SetErrorType(ErrorType errorType) {m_errorType = errorType;}

private:
        ErrorType m_errorType;
        std::string m_what;
};

//! exception thrown when an invalid argument is detected
class CRYPTOPP_DLL InvalidArgument : public Exception
{
public:
        explicit InvalidArgument(const std::string &s) : Exception(INVALID_ARGUMENT, s) {}
};

//! exception thrown when input data is received that doesn't conform to expected format
class CRYPTOPP_DLL InvalidDataFormat : public Exception
{
public:
        explicit InvalidDataFormat(const std::string &s) : Exception(INVALID_DATA_FORMAT, s) {}
};

//! exception thrown by decryption filters when trying to decrypt an invalid ciphertext
class CRYPTOPP_DLL InvalidCiphertext : public InvalidDataFormat
{
public:
        explicit InvalidCiphertext(const std::string &s) : InvalidDataFormat(s) {}
};

//! exception thrown by a class if a non-implemented method is called
class CRYPTOPP_DLL NotImplemented : public Exception
{
public:
        explicit NotImplemented(const std::string &s) : Exception(NOT_IMPLEMENTED, s) {}
};

//! exception thrown by a class when Flush(true) is called but it can't completely flush its buffers
class CRYPTOPP_DLL CannotFlush : public Exception
{
public:
        explicit CannotFlush(const std::string &s) : Exception(CANNOT_FLUSH, s) {}
};

//! error reported by the operating system
class CRYPTOPP_DLL OS_Error : public Exception
{
public:
        OS_Error(ErrorType errorType, const std::string &s, const std::string& operation, int errorCode)
                : Exception(errorType, s), m_operation(operation), m_errorCode(errorCode) {}
        ~OS_Error() throw() {}

        // the operating system API that reported the error
        const std::string & GetOperation() const {return m_operation;}
        // the error code return by the operating system
        int GetErrorCode() const {return m_errorCode;}

protected:
        std::string m_operation;
        int m_errorCode;
};

//! used to return decoding results
struct CRYPTOPP_DLL DecodingResult
{
        explicit DecodingResult() : isValidCoding(false), messageLength(0) {}
        explicit DecodingResult(size_t len) : isValidCoding(true), messageLength(len) {}

        bool operator==(const DecodingResult &rhs) const {return isValidCoding == rhs.isValidCoding && messageLength == rhs.messageLength;}
        bool operator!=(const DecodingResult &rhs) const {return !operator==(rhs);}

        bool isValidCoding;
        size_t messageLength;

#ifdef CRYPTOPP_MAINTAIN_BACKWARDS_COMPATIBILITY
        operator size_t() const {return isValidCoding ? messageLength : 0;}
#endif
};

//! interface for retrieving values given their names
/*! \note This class is used to safely pass a variable number of arbitrarily typed arguments to functions
        and to read values from keys and crypto parameters.
        \note To obtain an object that implements NameValuePairs for the purpose of parameter
        passing, use the MakeParameters() function.
        \note To get a value from NameValuePairs, you need to know the name and the type of the value. 
        Call GetValueNames() on a NameValuePairs object to obtain a list of value names that it supports.
        Then look at the Name namespace documentation to see what the type of each value is, or
        alternatively, call GetIntValue() with the value name, and if the type is not int, a
        ValueTypeMismatch exception will be thrown and you can get the actual type from the exception object.
*/
class CRYPTOPP_NO_VTABLE NameValuePairs
{
public:
        virtual ~NameValuePairs() {}

        //! exception thrown when trying to retrieve a value using a different type than expected
        class CRYPTOPP_DLL ValueTypeMismatch : public InvalidArgument
        {
        public:
                ValueTypeMismatch(const std::string &name, const std::type_info &stored, const std::type_info &retrieving)
                        : InvalidArgument("NameValuePairs: type mismatch for '" + name + "', stored '" + stored.name() + "', trying to retrieve '" + retrieving.name() + "'")
                        , m_stored(stored), m_retrieving(retrieving) {}

                const std::type_info & GetStoredTypeInfo() const {return m_stored;}
                const std::type_info & GetRetrievingTypeInfo() const {return m_retrieving;}

        private:
                const std::type_info &m_stored;
                const std::type_info &m_retrieving;
        };

        //! get a copy of this object or a subobject of it
        template <class T>
        bool GetThisObject(T &object) const
        {
                return GetValue((std::string("ThisObject:")+typeid(T).name()).c_str(), object);
        }

        //! get a pointer to this object, as a pointer to T
        template <class T>
        bool GetThisPointer(T *&p) const
        {
                return GetValue((std::string("ThisPointer:")+typeid(T).name()).c_str(), p);
        }

        //! get a named value, returns true if the name exists
        template <class T>
        bool GetValue(const char *name, T &value) const
        {
                return GetVoidValue(name, typeid(T), &value);
        }

        //! get a named value, returns the default if the name doesn't exist
        template <class T>
        T GetValueWithDefault(const char *name, T defaultValue) const
        {
                GetValue(name, defaultValue);
                return defaultValue;
        }

        //! get a list of value names that can be retrieved
        CRYPTOPP_DLL std::string GetValueNames() const
                {std::string result; GetValue("ValueNames", result); return result;}

        //! get a named value with type int
        /*! used to ensure we don't accidentally try to get an unsigned int
                or some other type when we mean int (which is the most common case) */
        CRYPTOPP_DLL bool GetIntValue(const char *name, int &value) const
                {return GetValue(name, value);}

        //! get a named value with type int, with default
        CRYPTOPP_DLL int GetIntValueWithDefault(const char *name, int defaultValue) const
                {return GetValueWithDefault(name, defaultValue);}

        //! used by derived classes to check for type mismatch
        CRYPTOPP_DLL static void CRYPTOPP_API ThrowIfTypeMismatch(const char *name, const std::type_info &stored, const std::type_info &retrieving)
                {if (stored != retrieving) throw ValueTypeMismatch(name, stored, retrieving);}

        template <class T>
        void GetRequiredParameter(const char *className, const char *name, T &value) const
        {
                if (!GetValue(name, value))
                        throw InvalidArgument(std::string(className) + ": missing required parameter '" + name + "'");
        }

        CRYPTOPP_DLL void GetRequiredIntParameter(const char *className, const char *name, int &value) const
        {
                if (!GetIntValue(name, value))
                        throw InvalidArgument(std::string(className) + ": missing required parameter '" + name + "'");
        }

        //! to be implemented by derived classes, users should use one of the above functions instead
        CRYPTOPP_DLL virtual bool GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const =0;
};

//! namespace containing value name definitions
/*!     value names, types and semantics:

        ThisObject:ClassName (ClassName, copy of this object or a subobject)
        ThisPointer:ClassName (const ClassName *, pointer to this object or a subobject)
*/
DOCUMENTED_NAMESPACE_BEGIN(Name)
// more names defined in argnames.h
DOCUMENTED_NAMESPACE_END

//! empty set of name-value pairs
class CRYPTOPP_DLL NullNameValuePairs : public NameValuePairs
{
public:
        bool GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const {return false;}
};

//! _
extern CRYPTOPP_DLL const NullNameValuePairs g_nullNameValuePairs;

// ********************************************************

//! interface for cloning objects, this is not implemented by most classes yet
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE Clonable
{
public:
        virtual ~Clonable() {}
        //! this is not implemented by most classes yet
        virtual Clonable* Clone() const {throw NotImplemented("Clone() is not implemented yet.");}      // TODO: make this =0
};

//! interface for all crypto algorithms

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE Algorithm : public Clonable
{
public:
        /*! When FIPS 140-2 compliance is enabled and checkSelfTestStatus == true,
                this constructor throws SelfTestFailure if the self test hasn't been run or fails. */
        Algorithm(bool checkSelfTestStatus = true);
        //! returns name of this algorithm, not universally implemented yet
        virtual std::string AlgorithmName() const {return "unknown";}
};

//! keying interface for crypto algorithms that take byte strings as keys
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE SimpleKeyingInterface
{
public:
        virtual ~SimpleKeyingInterface() {}

        //! returns smallest valid key length in bytes */
        virtual size_t MinKeyLength() const =0;
        //! returns largest valid key length in bytes */
        virtual size_t MaxKeyLength() const =0;
        //! returns default (recommended) key length in bytes */
        virtual size_t DefaultKeyLength() const =0;

        //! returns the smallest valid key length in bytes that is >= min(n, GetMaxKeyLength())
        virtual size_t GetValidKeyLength(size_t n) const =0;

        //! returns whether n is a valid key length
        virtual bool IsValidKeyLength(size_t n) const
                {return n == GetValidKeyLength(n);}

        //! set or reset the key of this object
        /*! \param params is used to specify Rounds, BlockSize, etc. */
        virtual void SetKey(const byte *key, size_t length, const NameValuePairs &params = g_nullNameValuePairs);

        //! calls SetKey() with an NameValuePairs object that just specifies "Rounds"
        void SetKeyWithRounds(const byte *key, size_t length, int rounds);

        //! calls SetKey() with an NameValuePairs object that just specifies "IV"
        void SetKeyWithIV(const byte *key, size_t length, const byte *iv, size_t ivLength);

        //! calls SetKey() with an NameValuePairs object that just specifies "IV"
        void SetKeyWithIV(const byte *key, size_t length, const byte *iv)
                {SetKeyWithIV(key, length, iv, IVSize());}

        enum IV_Requirement {UNIQUE_IV = 0, RANDOM_IV, UNPREDICTABLE_RANDOM_IV, INTERNALLY_GENERATED_IV, NOT_RESYNCHRONIZABLE};
        //! returns the minimal requirement for secure IVs
        virtual IV_Requirement IVRequirement() const =0;

        //! returns whether this object can be resynchronized (i.e. supports initialization vectors)
        /*! If this function returns true, and no IV is passed to SetKey() and CanUseStructuredIVs()==true, an IV of all 0's will be assumed. */
        bool IsResynchronizable() const {return IVRequirement() < NOT_RESYNCHRONIZABLE;}
        //! returns whether this object can use random IVs (in addition to ones returned by GetNextIV)
        bool CanUseRandomIVs() const {return IVRequirement() <= UNPREDICTABLE_RANDOM_IV;}
        //! returns whether this object can use random but possibly predictable IVs (in addition to ones returned by GetNextIV)
        bool CanUsePredictableIVs() const {return IVRequirement() <= RANDOM_IV;}
        //! returns whether this object can use structured IVs, for example a counter (in addition to ones returned by GetNextIV)
        bool CanUseStructuredIVs() const {return IVRequirement() <= UNIQUE_IV;}

        virtual unsigned int IVSize() const {throw NotImplemented(GetAlgorithm().AlgorithmName() + ": this object doesn't support resynchronization");}
        //! returns default length of IVs accepted by this object
        unsigned int DefaultIVLength() const {return IVSize();}
        //! returns minimal length of IVs accepted by this object
        virtual unsigned int MinIVLength() const {return IVSize();}
        //! returns maximal length of IVs accepted by this object
        virtual unsigned int MaxIVLength() const {return IVSize();}
        //! resynchronize with an IV. ivLength=-1 means use IVSize()
        virtual void Resynchronize(const byte *iv, int ivLength=-1) {throw NotImplemented(GetAlgorithm().AlgorithmName() + ": this object doesn't support resynchronization");}
        //! get a secure IV for the next message
        /*! This method should be called after you finish encrypting one message and are ready to start the next one.
                After calling it, you must call SetKey() or Resynchronize() before using this object again. 
                This method is not implemented on decryption objects. */
        virtual void GetNextIV(RandomNumberGenerator &rng, byte *IV);

protected:
        virtual const Algorithm & GetAlgorithm() const =0;
        virtual void UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params) =0;

        void ThrowIfInvalidKeyLength(size_t length);
        void ThrowIfResynchronizable();                 // to be called when no IV is passed
        void ThrowIfInvalidIV(const byte *iv);  // check for NULL IV if it can't be used
        size_t ThrowIfInvalidIVLength(int size);
        const byte * GetIVAndThrowIfInvalid(const NameValuePairs &params, size_t &size);
        inline void AssertValidKeyLength(size_t length) const
                {assert(IsValidKeyLength(length));}
};

//! interface for the data processing part of block ciphers

/*! Classes derived from BlockTransformation are block ciphers
        in ECB mode (for example the DES::Encryption class), which are stateless.
        These classes should not be used directly, but only in combination with
        a mode class (see CipherModeDocumentation in modes.h).
*/
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE BlockTransformation : public Algorithm
{
public:
        //! encrypt or decrypt inBlock, xor with xorBlock, and write to outBlock
        virtual void ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const =0;

        //! encrypt or decrypt one block
        /*! \pre size of inBlock and outBlock == BlockSize() */
        void ProcessBlock(const byte *inBlock, byte *outBlock) const
                {ProcessAndXorBlock(inBlock, NULL, outBlock);}

        //! encrypt or decrypt one block in place
        void ProcessBlock(byte *inoutBlock) const
                {ProcessAndXorBlock(inoutBlock, NULL, inoutBlock);}

        //! block size of the cipher in bytes
        virtual unsigned int BlockSize() const =0;

        //! returns how inputs and outputs should be aligned for optimal performance
        virtual unsigned int OptimalDataAlignment() const;

        //! returns true if this is a permutation (i.e. there is an inverse transformation)
        virtual bool IsPermutation() const {return true;}

        //! returns true if this is an encryption object
        virtual bool IsForwardTransformation() const =0;

        //! return number of blocks that can be processed in parallel, for bit-slicing implementations
        virtual unsigned int OptimalNumberOfParallelBlocks() const {return 1;}

        enum {BT_InBlockIsCounter=1, BT_DontIncrementInOutPointers=2, BT_XorInput=4, BT_ReverseDirection=8} FlagsForAdvancedProcessBlocks;

        //! encrypt and xor blocks according to flags (see FlagsForAdvancedProcessBlocks)
        /*! /note If BT_InBlockIsCounter is set, last byte of inBlocks may be modified. */
        virtual size_t AdvancedProcessBlocks(const byte *inBlocks, const byte *xorBlocks, byte *outBlocks, size_t length, word32 flags) const;

        inline CipherDir GetCipherDirection() const {return IsForwardTransformation() ? ENCRYPTION : DECRYPTION;}
};

//! interface for the data processing part of stream ciphers

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE StreamTransformation : public Algorithm
{
public:
        //! return a reference to this object, 
        /*! This function is useful for passing a temporary StreamTransformation object to a 
                function that takes a non-const reference. */
        StreamTransformation& Ref() {return *this;}

        //! returns block size, if input must be processed in blocks, otherwise 1
        virtual unsigned int MandatoryBlockSize() const {return 1;}

        //! returns the input block size that is most efficient for this cipher
        /*! \note optimal input length is n * OptimalBlockSize() - GetOptimalBlockSizeUsed() for any n > 0 */
        virtual unsigned int OptimalBlockSize() const {return MandatoryBlockSize();}
        //! returns how much of the current block is used up
        virtual unsigned int GetOptimalBlockSizeUsed() const {return 0;}

        //! returns how input should be aligned for optimal performance
        virtual unsigned int OptimalDataAlignment() const;

        //! encrypt or decrypt an array of bytes of specified length
        /*! \note either inString == outString, or they don't overlap */
        virtual void ProcessData(byte *outString, const byte *inString, size_t length) =0;

        //! for ciphers where the last block of data is special, encrypt or decrypt the last block of data
        /*! For now the only use of this function is for CBC-CTS mode. */
        virtual void ProcessLastBlock(byte *outString, const byte *inString, size_t length);
        //! returns the minimum size of the last block, 0 indicating the last block is not special
        virtual unsigned int MinLastBlockSize() const {return 0;}

        //! same as ProcessData(inoutString, inoutString, length)
        inline void ProcessString(byte *inoutString, size_t length)
                {ProcessData(inoutString, inoutString, length);}
        //! same as ProcessData(outString, inString, length)
        inline void ProcessString(byte *outString, const byte *inString, size_t length)
                {ProcessData(outString, inString, length);}
        //! implemented as {ProcessData(&input, &input, 1); return input;}
        inline byte ProcessByte(byte input)
                {ProcessData(&input, &input, 1); return input;}

        //! returns whether this cipher supports random access
        virtual bool IsRandomAccess() const =0;
        //! for random access ciphers, seek to an absolute position
        virtual void Seek(lword n)
        {
                assert(!IsRandomAccess());
                throw NotImplemented("StreamTransformation: this object doesn't support random access");
        }

        //! returns whether this transformation is self-inverting (e.g. xor with a keystream)
        virtual bool IsSelfInverting() const =0;
        //! returns whether this is an encryption object
        virtual bool IsForwardTransformation() const =0;
};

//! interface for hash functions and data processing part of MACs

/*! HashTransformation objects are stateful.  They are created in an initial state,
        change state as Update() is called, and return to the initial
        state when Final() is called.  This interface allows a large message to
        be hashed in pieces by calling Update() on each piece followed by
        calling Final().
*/
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE HashTransformation : public Algorithm
{
public:
        //! return a reference to this object, 
        /*! This function is useful for passing a temporary HashTransformation object to a 
                function that takes a non-const reference. */
        HashTransformation& Ref() {return *this;}

        //! process more input
        virtual void Update(const byte *input, size_t length) =0;

        //! request space to write input into
        virtual byte * CreateUpdateSpace(size_t &size) {size=0; return NULL;}

        //! compute hash for current message, then restart for a new message
        /*!     \pre size of digest == DigestSize(). */
        virtual void Final(byte *digest)
                {TruncatedFinal(digest, DigestSize());}

        //! discard the current state, and restart with a new message
        virtual void Restart()
                {TruncatedFinal(NULL, 0);}

        //! size of the hash/digest/MAC returned by Final()
        virtual unsigned int DigestSize() const =0;

        //! same as DigestSize()
        unsigned int TagSize() const {return DigestSize();}


        //! block size of underlying compression function, or 0 if not block based
        virtual unsigned int BlockSize() const {return 0;}

        //! input to Update() should have length a multiple of this for optimal speed
        virtual unsigned int OptimalBlockSize() const {return 1;}

        //! returns how input should be aligned for optimal performance
        virtual unsigned int OptimalDataAlignment() const;

        //! use this if your input is in one piece and you don't want to call Update() and Final() separately
        virtual void CalculateDigest(byte *digest, const byte *input, size_t length)
                {Update(input, length); Final(digest);}

        //! verify that digest is a valid digest for the current message, then reinitialize the object
        /*! Default implementation is to call Final() and do a bitwise comparison
                between its output and digest. */
        virtual bool Verify(const byte *digest)
                {return TruncatedVerify(digest, DigestSize());}

        //! use this if your input is in one piece and you don't want to call Update() and Verify() separately
        virtual bool VerifyDigest(const byte *digest, const byte *input, size_t length)
                {Update(input, length); return Verify(digest);}

        //! truncated version of Final()
        virtual void TruncatedFinal(byte *digest, size_t digestSize) =0;

        //! truncated version of CalculateDigest()
        virtual void CalculateTruncatedDigest(byte *digest, size_t digestSize, const byte *input, size_t length)
                {Update(input, length); TruncatedFinal(digest, digestSize);}

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

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

protected:
        void ThrowIfInvalidTruncatedSize(size_t size) const;
};

typedef HashTransformation HashFunction;

//! 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 CRYPTOPP_DLL CRYPTOPP_NO_VTABLE BlockCipher : public SimpleKeyingInterface, public BlockTransformation
{
protected:
        const Algorithm & GetAlgorithm() const {return *this;}
};

//! interface for one direction (encryption or decryption) of a stream cipher or cipher mode
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE SymmetricCipher : public SimpleKeyingInterface, public StreamTransformation
{
protected:
        const Algorithm & GetAlgorithm() const {return *this;}
};

//! interface for message authentication codes
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE MessageAuthenticationCode : public SimpleKeyingInterface, public HashTransformation
{
protected:
        const Algorithm & GetAlgorithm() const {return *this;}
};

//! interface for for one direction (encryption or decryption) of a stream cipher or block cipher mode with authentication
/*! The StreamTransformation part of this interface is used to encrypt/decrypt the data, and the MessageAuthenticationCode part of this
        interface is used to input additional authenticated data (AAD, which is MAC'ed but not encrypted), and to generate/verify the MAC. */
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE AuthenticatedSymmetricCipher : public MessageAuthenticationCode, public StreamTransformation
{
public:
        //! this indicates that a member function was called in the wrong state, for example trying to encrypt a message before having set the key or IV
        class BadState : public Exception
        {
        public:
                explicit BadState(const std::string &name, const char *message) : Exception(OTHER_ERROR, name + ": " + message) {}
                explicit BadState(const std::string &name, const char *function, const char *state) : Exception(OTHER_ERROR, name + ": " + function + " was called before " + state) {}
        };

        //! the maximum length of AAD that can be input before the encrypted data
        virtual lword MaxHeaderLength() const =0;
        //! the maximum length of encrypted data
        virtual lword MaxMessageLength() const =0;
        //! the maximum length of AAD that can be input after the encrypted data
        virtual lword MaxFooterLength() const {return 0;}
        //! if this function returns true, SpecifyDataLengths() must be called before attempting to input data
        /*! This is the case for some schemes, such as CCM. */
        virtual bool NeedsPrespecifiedDataLengths() const {return false;}
        //! this function only needs to be called if NeedsPrespecifiedDataLengths() returns true
        void SpecifyDataLengths(lword headerLength, lword messageLength, lword footerLength=0);
        //! encrypt and generate MAC in one call. will truncate MAC if macSize < TagSize()
        virtual void EncryptAndAuthenticate(byte *ciphertext, byte *mac, size_t macSize, const byte *iv, int ivLength, const byte *header, size_t headerLength, const byte *message, size_t messageLength);
        //! decrypt and verify MAC in one call, returning true iff MAC is valid. will assume MAC is truncated if macLength < TagSize()
        virtual bool DecryptAndVerify(byte *message, const byte *mac, size_t macLength, const byte *iv, int ivLength, const byte *header, size_t headerLength, const byte *ciphertext, size_t ciphertextLength);

        // redeclare this to avoid compiler ambiguity errors
        virtual std::string AlgorithmName() const =0;

protected:
        const Algorithm & GetAlgorithm() const {return *static_cast<const MessageAuthenticationCode *>(this);}
        virtual void UncheckedSpecifyDataLengths(lword headerLength, lword messageLength, lword footerLength) {}
};

#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:
        //! update RNG state with additional unpredictable values
        virtual void IncorporateEntropy(const byte *input, size_t length) {throw NotImplemented("RandomNumberGenerator: IncorporateEntropy not implemented");}

        //! returns true if IncorporateEntropy is implemented
        virtual bool CanIncorporateEntropy() const {return false;}

        //! generate new random byte and return it
        virtual byte GenerateByte();

        //! generate new random bit and return it
        /*! Default implementation is to call GenerateByte() and return its lowest bit. */
        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
        virtual void GenerateBlock(byte *output, size_t size);

        //! generate and discard n bytes
        virtual void DiscardBytes(size_t n);

        //! generate random bytes as input to a BufferedTransformation
        virtual void GenerateIntoBufferedTransformation(BufferedTransformation &target, const std::string &channel, lword length);

        //! 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, size_t 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 & CRYPTOPP_API NullRNG();

class WaitObjectContainer;
class CallStack;

//! interface for objects that you can wait for

class CRYPTOPP_NO_VTABLE Waitable
{
public:
        virtual ~Waitable() {}

        //! maximum number of wait objects that this object can return
        virtual unsigned int GetMaxWaitObjectCount() const =0;
        //! put wait objects into container
        /*! \param callStack is used for tracing no wait loops, example:
                     something.GetWaitObjects(c, CallStack("my func after X", 0));
                           - or in an outer GetWaitObjects() method that itself takes a callStack parameter:
                             innerThing.GetWaitObjects(c, CallStack("MyClass::GetWaitObjects at X", &callStack)); */
        virtual void GetWaitObjects(WaitObjectContainer &container, CallStack const& callStack) =0;
        //! wait on this object
        /*! same as creating an empty container, calling GetWaitObjects(), and calling Wait() on the container */
        bool Wait(unsigned long milliseconds, CallStack const& callStack);
};

//! the default channel for BufferedTransformation, equal to the empty string
extern CRYPTOPP_DLL const std::string DEFAULT_CHANNEL;

//! channel for additional authenticated data, equal to "AAD"
extern CRYPTOPP_DLL const std::string AAD_CHANNEL;

//! 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; // same as DEFAULT_CHANNEL, for backwards compatibility

        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
                size_t Put(byte inByte, bool blocking=true)
                        {return Put(&inByte, 1, blocking);}
                //! input multiple bytes
                size_t Put(const byte *inString, size_t length, bool blocking=true)
                        {return Put2(inString, length, 0, blocking);}

                //! input a 16-bit word
                size_t PutWord16(word16 value, ByteOrder order=BIG_ENDIAN_ORDER, bool blocking=true);
                //! input a 32-bit word
                size_t 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(size_t &size) {size=0; return NULL;}

                virtual bool CanModifyInput() const {return false;}

                //! input multiple bytes that may be modified by callee
                size_t PutModifiable(byte *inString, size_t 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);}
                size_t PutMessageEnd(const byte *inString, size_t 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 size_t Put2(const byte *inString, size_t 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 size_t PutModifiable2(byte *inString, size_t 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, CallStack const& callStack);
        //@}

        //!     \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 lword MaxRetrievable() const;

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

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

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

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

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

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

                //! discard skipMax bytes from the output buffer
                virtual lword Skip(lword skipMax=LWORD_MAX);

                //! copy copyMax bytes of the buffered output to target as input
                lword CopyTo(BufferedTransformation &target, lword copyMax=LWORD_MAX, const std::string &channel=DEFAULT_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
                lword CopyRangeTo(BufferedTransformation &target, lword position, lword copyMax=LWORD_MAX, const std::string &channel=DEFAULT_CHANNEL) const
                        {lword 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 lword TotalBytesRetrievable() const;
                //! number of times MessageEnd() has been received minus messages retrieved or skipped
                virtual unsigned int NumberOfMessages() const;
                //! returns true if NumberOfMessages() > 0
                virtual bool AnyMessages() const;
                //! start retrieving the next message
                /*!
                        Returns false if no more messages exist or this message 
                        is not completely retrieved.
                */
                virtual bool GetNextMessage();
                //! skip count number of messages
                virtual unsigned int SkipMessages(unsigned int count=UINT_MAX);
                //!
                unsigned int TransferMessagesTo(BufferedTransformation &target, unsigned int count=UINT_MAX, const std::string &channel=DEFAULT_CHANNEL)
                        {TransferMessagesTo2(target, count, channel); return count;}
                //!
                unsigned int CopyMessagesTo(BufferedTransformation &target, unsigned int count=UINT_MAX, const std::string &channel=DEFAULT_CHANNEL) const;

                //!
                virtual void SkipAll();
                //!
                void TransferAllTo(BufferedTransformation &target, const std::string &channel=DEFAULT_CHANNEL)
                        {TransferAllTo2(target, channel);}
                //!
                void CopyAllTo(BufferedTransformation &target, const std::string &channel=DEFAULT_CHANNEL) const;

                virtual bool GetNextMessageSeries() {return false;}
                virtual unsigned int NumberOfMessagesInThisSeries() const {return NumberOfMessages();}
                virtual unsigned int NumberOfMessageSeries() const {return 0;}
        //@}

        //!     \name NON-BLOCKING TRANSFER OF OUTPUT
        //@{
                //! upon return, byteCount contains number of bytes that have finished being transfered, and returns the number of bytes left in the current transfer block
                virtual size_t TransferTo2(BufferedTransformation &target, lword &byteCount, const std::string &channel=DEFAULT_CHANNEL, bool blocking=true) =0;
                //! upon return, begin contains the start position of data yet to be finished copying, and returns the number of bytes left in the current transfer block
                virtual size_t CopyRangeTo2(BufferedTransformation &target, lword &begin, lword end=LWORD_MAX, const std::string &channel=DEFAULT_CHANNEL, bool blocking=true) const =0;
                //! upon return, messageCount contains number of messages that have finished being transfered, and returns the number of bytes left in the current transfer block
                size_t TransferMessagesTo2(BufferedTransformation &target, unsigned int &messageCount, const std::string &channel=DEFAULT_CHANNEL, bool blocking=true);
                //! returns the number of bytes left in the current transfer block
                size_t TransferAllTo2(BufferedTransformation &target, const std::string &channel=DEFAULT_CHANNEL, bool blocking=true);
        //@}

        //!     \name CHANNELS
        //@{
                struct NoChannelSupport : public NotImplemented
                        {NoChannelSupport(const std::string &name) : NotImplemented(name + ": this object doesn't support multiple channels") {}};
                struct InvalidChannelName : public InvalidArgument
                        {InvalidChannelName(const std::string &name, const std::string &channel) : InvalidArgument(name + ": unexpected channel name \"" + channel + "\"") {}};

                size_t ChannelPut(const std::string &channel, byte inByte, bool blocking=true)
                        {return ChannelPut(channel, &inByte, 1, blocking);}
                size_t ChannelPut(const std::string &channel, const byte *inString, size_t length, bool blocking=true)
                        {return ChannelPut2(channel, inString, length, 0, blocking);}

                size_t ChannelPutModifiable(const std::string &channel, byte *inString, size_t length, bool blocking=true)
                        {return ChannelPutModifiable2(channel, inString, length, 0, blocking);}

                size_t ChannelPutWord16(const std::string &channel, word16 value, ByteOrder order=BIG_ENDIAN_ORDER, bool blocking=true);
                size_t ChannelPutWord32(const std::string &channel, word32 value, ByteOrder order=BIG_ENDIAN_ORDER, bool blocking=true);

                bool ChannelMessageEnd(const std::string &channel, int propagation=-1, bool blocking=true)
                        {return !!ChannelPut2(channel, NULL, 0, propagation < 0 ? -1 : propagation+1, blocking);}
                size_t ChannelPutMessageEnd(const std::string &channel, const byte *inString, size_t length, int propagation=-1, bool blocking=true)
                        {return ChannelPut2(channel, inString, length, propagation < 0 ? -1 : propagation+1, blocking);}

                virtual byte * ChannelCreatePutSpace(const std::string &channel, size_t &size);

                virtual size_t ChannelPut2(const std::string &channel, const byte *begin, size_t length, int messageEnd, bool blocking);
                virtual size_t ChannelPutModifiable2(const std::string &channel, byte *begin, size_t length, int messageEnd, bool blocking);

                virtual bool ChannelFlush(const std::string &channel, bool hardFlush, int propagation=-1, bool blocking=true);
                virtual bool ChannelMessageSeriesEnd(const std::string &channel, int propagation=-1, bool blocking=true);

                virtual void SetRetrievalChannel(const std::string &channel);
        //@}

        //!     \name ATTACHMENT
        /*! Some BufferedTransformation objects (e.g. Filter objects)
                allow other BufferedTransformation objects to be attached. When
                this is done, the first object instead of buffering its output,
                sents that output to the attached object as input. The entire
                attachment chain is deleted when the anchor object is destructed.
        */
        //@{
                //! returns whether this object allows attachment
                virtual bool Attachable() {return false;}
                //! returns the object immediately attached to this object or NULL for no attachment
                virtual BufferedTransformation *AttachedTransformation() {assert(!Attachable()); return 0;}
                //!
                virtual const BufferedTransformation *AttachedTransformation() const
                        {return const_cast<BufferedTransformation *>(this)->AttachedTransformation();}
                //! delete the current attachment chain and replace it with newAttachment
                virtual void Detach(BufferedTransformation *newAttachment = 0)
                        {assert(!Attachable()); throw NotImplemented("BufferedTransformation: this object is not attachable");}
                //! add newAttachment to the end of attachment chain
                virtual void Attach(BufferedTransformation *newAttachment);
        //@}

protected:
        static int DecrementPropagation(int propagation)
                {return propagation != 0 ? propagation - 1 : 0;}

private:
        byte m_buf[4];  // for ChannelPutWord16 and ChannelPutWord32, to ensure buffer isn't deallocated before non-blocking operation completes
};

//! returns a reference to a BufferedTransformation object that discards all input
BufferedTransformation & TheBitBucket();

//! interface for crypto material, such as public and private keys, and crypto parameters

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE CryptoMaterial : public NameValuePairs
{
public:
        //! exception thrown when invalid crypto material is detected
        class CRYPTOPP_DLL InvalidMaterial : public InvalidDataFormat
        {
        public:
                explicit InvalidMaterial(const std::string &s) : InvalidDataFormat(s) {}
        };

        //! assign values from source to this object
        /*! \note This function can be used to create a public key from a private key. */
        virtual void AssignFrom(const NameValuePairs &source) =0;

        //! check this object for errors
        /*! \param level denotes the level of thoroughness:
                0 - using this object won't cause a crash or exception (rng is ignored)
                1 - this object will probably function (encrypt, sign, etc.) correctly (but may not check for weak keys and such)
                2 - make sure this object will function correctly, and do reasonable security checks
                3 - do checks that may take a long time
                \return true if the tests pass */
        virtual bool Validate(RandomNumberGenerator &rng, unsigned int level) const =0;

        //! throws InvalidMaterial if this object fails Validate() test
        virtual void ThrowIfInvalid(RandomNumberGenerator &rng, unsigned int level) const
                {if (!Validate(rng, level)) throw InvalidMaterial("CryptoMaterial: this object contains invalid values");}

//      virtual std::vector<std::string> GetSupportedFormats(bool includeSaveOnly=false, bool includeLoadOnly=false);

        //! save key into a BufferedTransformation
        virtual void Save(BufferedTransformation &bt) const
                {throw NotImplemented("CryptoMaterial: this object does not support saving");}

        //! load key from a BufferedTransformation
        /*! \throws KeyingErr if decode fails
                \note Generally does not check that the key is valid.
                        Call ValidateKey() or ThrowIfInvalidKey() to check that. */
        virtual void Load(BufferedTransformation &bt)
                {throw NotImplemented("CryptoMaterial: this object does not support loading");}

        //! \return whether this object supports precomputation
        virtual bool SupportsPrecomputation() const {return false;}
        //! do precomputation
        /*! The exact semantics of Precompute() is varies, but
                typically it means calculate a table of n objects
                that can be used later to speed up computation. */
        virtual void Precompute(unsigned int n)
                {assert(!SupportsPrecomputation()); throw NotImplemented("CryptoMaterial: this object does not support precomputation");}
        //! retrieve previously saved precomputation
        virtual void LoadPrecomputation(BufferedTransformation &storedPrecomputation)
                {assert(!SupportsPrecomputation()); throw NotImplemented("CryptoMaterial: this object does not support precomputation");}
        //! save precomputation for later use
        virtual void SavePrecomputation(BufferedTransformation &storedPrecomputation) const
                {assert(!SupportsPrecomputation()); throw NotImplemented("CryptoMaterial: this object does not support precomputation");}

        // for internal library use
        void DoQuickSanityCheck() const {ThrowIfInvalid(NullRNG(), 0);}

#if (defined(__SUNPRO_CC) && __SUNPRO_CC < 0x590)
        // Sun Studio 11/CC 5.8 workaround: it generates incorrect code when casting to an empty virtual base class
        char m_sunCCworkaround;
#endif
};

//! interface for generatable crypto material, such as private keys and crypto parameters

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE GeneratableCryptoMaterial : virtual public CryptoMaterial
{
public:
        //! generate a random key or crypto parameters
        /*! \throws KeyingErr if algorithm parameters are invalid, or if a key can't be generated
                (e.g., if this is a public key object) */
        virtual void GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &params = g_nullNameValuePairs)
                {throw NotImplemented("GeneratableCryptoMaterial: this object does not support key/parameter generation");}

        //! calls the above function with a NameValuePairs object that just specifies "KeySize"
        void GenerateRandomWithKeySize(RandomNumberGenerator &rng, unsigned int keySize);
};

//! interface for public keys

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE PublicKey : virtual public CryptoMaterial
{
};

//! interface for private keys

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE PrivateKey : public GeneratableCryptoMaterial
{
};

//! interface for crypto prameters

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE CryptoParameters : public GeneratableCryptoMaterial
{
};

//! interface for asymmetric algorithms

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE AsymmetricAlgorithm : public Algorithm
{
public:
        //! returns a reference to the crypto material used by this object
        virtual CryptoMaterial & AccessMaterial() =0;
        //! returns a const reference to the crypto material used by this object
        virtual const CryptoMaterial & GetMaterial() const =0;

        //! for backwards compatibility, calls AccessMaterial().Load(bt)
        void BERDecode(BufferedTransformation &bt)
                {AccessMaterial().Load(bt);}
        //! for backwards compatibility, calls GetMaterial().Save(bt)
        void DEREncode(BufferedTransformation &bt) const
                {GetMaterial().Save(bt);}
};

//! interface for asymmetric algorithms using public keys

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE PublicKeyAlgorithm : public AsymmetricAlgorithm
{
public:
        // VC60 workaround: no co-variant return type
        CryptoMaterial & AccessMaterial() {return AccessPublicKey();}
        const CryptoMaterial & GetMaterial() const {return GetPublicKey();}

        virtual PublicKey & AccessPublicKey() =0;
        virtual const PublicKey & GetPublicKey() const {return const_cast<PublicKeyAlgorithm *>(this)->AccessPublicKey();}
};

//! interface for asymmetric algorithms using private keys

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE PrivateKeyAlgorithm : public AsymmetricAlgorithm
{
public:
        CryptoMaterial & AccessMaterial() {return AccessPrivateKey();}
        const CryptoMaterial & GetMaterial() const {return GetPrivateKey();}

        virtual PrivateKey & AccessPrivateKey() =0;
        virtual const PrivateKey & GetPrivateKey() const {return const_cast<PrivateKeyAlgorithm *>(this)->AccessPrivateKey();}
};

//! interface for key agreement algorithms

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE KeyAgreementAlgorithm : public AsymmetricAlgorithm
{
public:
        CryptoMaterial & AccessMaterial() {return AccessCryptoParameters();}
        const CryptoMaterial & GetMaterial() const {return GetCryptoParameters();}

        virtual CryptoParameters & AccessCryptoParameters() =0;
        virtual const CryptoParameters & GetCryptoParameters() const {return const_cast<KeyAgreementAlgorithm *>(this)->AccessCryptoParameters();}
};

//! interface for public-key encryptors and decryptors

/*! This class provides an interface common to encryptors and decryptors
        for querying their plaintext and ciphertext lengths.
*/
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE PK_CryptoSystem
{
public:
        virtual ~PK_CryptoSystem() {}

        //! maximum length of plaintext for a given ciphertext length
        /*! \note This function returns 0 if ciphertextLength is not valid (too long or too short). */
        virtual size_t MaxPlaintextLength(size_t ciphertextLength) const =0;

        //! calculate length of ciphertext given length of plaintext
        /*! \note This function returns 0 if plaintextLength is not valid (too long). */
        virtual size_t CiphertextLength(size_t plaintextLength) const =0;

        //! this object supports the use of the parameter with the given name
        /*! some possible parameter names: EncodingParameters, KeyDerivationParameters */
        virtual bool ParameterSupported(const char *name) const =0;

        //! return fixed ciphertext length, if one exists, otherwise return 0
        /*! \note "Fixed" here means length of ciphertext does not depend on length of plaintext.
                It usually does depend on the key length. */
        virtual size_t FixedCiphertextLength() const {return 0;}

        //! return maximum plaintext length given the fixed ciphertext length, if one exists, otherwise return 0
        virtual size_t FixedMaxPlaintextLength() const {return 0;}

#ifdef CRYPTOPP_MAINTAIN_BACKWARDS_COMPATIBILITY
        size_t MaxPlainTextLength(size_t cipherTextLength) const {return MaxPlaintextLength(cipherTextLength);}
        size_t CipherTextLength(size_t plainTextLength) const {return CiphertextLength(plainTextLength);}
#endif
};

//! interface for public-key encryptors
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE PK_Encryptor : public PK_CryptoSystem, public PublicKeyAlgorithm
{
public:
        //! exception thrown when trying to encrypt plaintext of invalid length
        class CRYPTOPP_DLL InvalidPlaintextLength : public Exception
        {
        public:
                InvalidPlaintextLength() : Exception(OTHER_ERROR, "PK_Encryptor: invalid plaintext length") {}
        };

        //! encrypt a byte string
        /*! \pre CiphertextLength(plaintextLength) != 0 (i.e., plaintext isn't too long)
                \pre size of ciphertext == CiphertextLength(plaintextLength)
        */
        virtual void Encrypt(RandomNumberGenerator &rng, 
                const byte *plaintext, size_t plaintextLength, 
                byte *ciphertext, const NameValuePairs &parameters = g_nullNameValuePairs) const =0;

        //! create a new encryption filter
        /*! \note The caller is responsible for deleting the returned pointer.
                \note Encoding parameters should be passed in the "EP" channel.
        */
        virtual BufferedTransformation * CreateEncryptionFilter(RandomNumberGenerator &rng, 
                BufferedTransformation *attachment=NULL, const NameValuePairs &parameters = g_nullNameValuePairs) const;
};

//! interface for public-key decryptors

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE PK_Decryptor : public PK_CryptoSystem, public PrivateKeyAlgorithm
{
public:
        //! decrypt a byte string, and return the length of plaintext
        /*! \pre size of plaintext == MaxPlaintextLength(ciphertextLength) bytes.
                \return the actual length of the plaintext, indication that decryption failed.
        */
        virtual DecodingResult Decrypt(RandomNumberGenerator &rng, 
                const byte *ciphertext, size_t ciphertextLength, 
                byte *plaintext, const NameValuePairs &parameters = g_nullNameValuePairs) const =0;

        //! create a new decryption filter
        /*! \note caller is responsible for deleting the returned pointer
        */
        virtual BufferedTransformation * CreateDecryptionFilter(RandomNumberGenerator &rng, 
                BufferedTransformation *attachment=NULL, const NameValuePairs &parameters = g_nullNameValuePairs) const;

        //! decrypt a fixed size ciphertext
        DecodingResult FixedLengthDecrypt(RandomNumberGenerator &rng, const byte *ciphertext, byte *plaintext, const NameValuePairs &parameters = g_nullNameValuePairs) const
                {return Decrypt(rng, ciphertext, FixedCiphertextLength(), plaintext, parameters);}
};

#ifdef CRYPTOPP_MAINTAIN_BACKWARDS_COMPATIBILITY
typedef PK_CryptoSystem PK_FixedLengthCryptoSystem;
typedef PK_Encryptor PK_FixedLengthEncryptor;
typedef PK_Decryptor PK_FixedLengthDecryptor;
#endif

//! interface for public-key signers and verifiers

/*! This class provides an interface common to signers and verifiers
        for querying scheme properties.
*/
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE PK_SignatureScheme
{
public:
        //! invalid key exception, may be thrown by any function in this class if the private or public key has a length that can't be used
        class CRYPTOPP_DLL InvalidKeyLength : public Exception
        {
        public:
                InvalidKeyLength(const std::string &message) : Exception(OTHER_ERROR, message) {}
        };

        //! key too short exception, may be thrown by any function in this class if the private or public key is too short to sign or verify anything
        class CRYPTOPP_DLL KeyTooShort : public InvalidKeyLength
        {
        public:
                KeyTooShort() : InvalidKeyLength("PK_Signer: key too short for this signature scheme") {}
        };

        virtual ~PK_SignatureScheme() {}

        //! signature length if it only depends on the key, otherwise 0
        virtual size_t SignatureLength() const =0;

        //! maximum signature length produced for a given length of recoverable message part
        virtual size_t MaxSignatureLength(size_t recoverablePartLength = 0) const {return SignatureLength();}

        //! length of longest message that can be recovered, or 0 if this signature scheme does not support message recovery
        virtual size_t MaxRecoverableLength() const =0;

        //! length of longest message that can be recovered from a signature of given length, or 0 if this signature scheme does not support message recovery
        virtual size_t MaxRecoverableLengthFromSignatureLength(size_t signatureLength) const =0;

        //! requires a random number generator to sign
        /*! if this returns false, NullRNG() can be passed to functions that take RandomNumberGenerator & */
        virtual bool IsProbabilistic() const =0;

        //! whether or not a non-recoverable message part can be signed
        virtual bool AllowNonrecoverablePart() const =0;

        //! if this function returns true, during verification you must input the signature before the message, otherwise you can input it at anytime */
        virtual bool SignatureUpfront() const {return false;}

        //! whether you must input the recoverable part before the non-recoverable part during signing
        virtual bool RecoverablePartFirst() const =0;
};

//! interface for accumulating messages to be signed or verified
/*! Only Update() should be called
        on this class. No other functions inherited from HashTransformation should be called.
*/
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE PK_MessageAccumulator : public HashTransformation
{
public:
        //! should not be called on PK_MessageAccumulator
        unsigned int DigestSize() const
                {throw NotImplemented("PK_MessageAccumulator: DigestSize() should not be called");}
        //! should not be called on PK_MessageAccumulator
        void TruncatedFinal(byte *digest, size_t digestSize) 
                {throw NotImplemented("PK_MessageAccumulator: TruncatedFinal() should not be called");}
};

//! interface for public-key signers

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE PK_Signer : public PK_SignatureScheme, public PrivateKeyAlgorithm
{
public:
        //! create a new HashTransformation to accumulate the message to be signed
        virtual PK_MessageAccumulator * NewSignatureAccumulator(RandomNumberGenerator &rng) const =0;

        virtual void InputRecoverableMessage(PK_MessageAccumulator &messageAccumulator, const byte *recoverableMessage, size_t recoverableMessageLength) const =0;

        //! sign and delete messageAccumulator (even in case of exception thrown)
        /*! \pre size of signature == MaxSignatureLength()
                \return actual signature length
        */
        virtual size_t Sign(RandomNumberGenerator &rng, PK_MessageAccumulator *messageAccumulator, byte *signature) const;

        //! sign and restart messageAccumulator
        /*! \pre size of signature == MaxSignatureLength()
                \return actual signature length
        */
        virtual size_t SignAndRestart(RandomNumberGenerator &rng, PK_MessageAccumulator &messageAccumulator, byte *signature, bool restart=true) const =0;

        //! sign a message
        /*! \pre size of signature == MaxSignatureLength()
                \return actual signature length
        */
        virtual size_t SignMessage(RandomNumberGenerator &rng, const byte *message, size_t messageLen, byte *signature) const;

        //! sign a recoverable message
        /*! \pre size of signature == MaxSignatureLength(recoverableMessageLength)
                \return actual signature length
        */
        virtual size_t SignMessageWithRecovery(RandomNumberGenerator &rng, const byte *recoverableMessage, size_t recoverableMessageLength, 
                const byte *nonrecoverableMessage, size_t nonrecoverableMessageLength, byte *signature) const;
};

//! interface for public-key signature verifiers
/*! The Recover* functions throw NotImplemented if the signature scheme does not support
        message recovery.
        The Verify* functions throw InvalidDataFormat if the scheme does support message
        recovery and the signature contains a non-empty recoverable message part. The
        Recovery* functions should be used in that case.
*/
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE PK_Verifier : public PK_SignatureScheme, public PublicKeyAlgorithm
{
public:
        //! create a new HashTransformation to accumulate the message to be verified
        virtual PK_MessageAccumulator * NewVerificationAccumulator() const =0;

        //! input signature into a message accumulator
        virtual void InputSignature(PK_MessageAccumulator &messageAccumulator, const byte *signature, size_t signatureLength) const =0;

        //! check whether messageAccumulator contains a valid signature and message, and delete messageAccumulator (even in case of exception thrown)
        virtual bool Verify(PK_MessageAccumulator *messageAccumulator) const;

        //! check whether messageAccumulator contains a valid signature and message, and restart messageAccumulator
        virtual bool VerifyAndRestart(PK_MessageAccumulator &messageAccumulator) const =0;

        //! check whether input signature is a valid signature for input message
        virtual bool VerifyMessage(const byte *message, size_t messageLen, 
                const byte *signature, size_t signatureLength) const;

        //! recover a message from its signature
        /*! \pre size of recoveredMessage == MaxRecoverableLengthFromSignatureLength(signatureLength)
        */
        virtual DecodingResult Recover(byte *recoveredMessage, PK_MessageAccumulator *messageAccumulator) const;

        //! recover a message from its signature
        /*! \pre size of recoveredMessage == MaxRecoverableLengthFromSignatureLength(signatureLength)
        */
        virtual DecodingResult RecoverAndRestart(byte *recoveredMessage, PK_MessageAccumulator &messageAccumulator) const =0;

        //! recover a message from its signature
        /*! \pre size of recoveredMessage == MaxRecoverableLengthFromSignatureLength(signatureLength)
        */
        virtual DecodingResult RecoverMessage(byte *recoveredMessage, 
                const byte *nonrecoverableMessage, size_t nonrecoverableMessageLength, 
                const byte *signature, size_t signatureLength) const;
};

//! interface for domains of simple key agreement protocols

/*! A key agreement domain is a set of parameters that must be shared
        by two parties in a key agreement protocol, along with the algorithms
        for generating key pairs and deriving agreed values.
*/
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE SimpleKeyAgreementDomain : public KeyAgreementAlgorithm
{
public:
        //! return length of agreed value produced
        virtual unsigned int AgreedValueLength() const =0;
        //! return length of private keys in this domain
        virtual unsigned int PrivateKeyLength() const =0;
        //! return length of public keys in this domain
        virtual unsigned int PublicKeyLength() const =0;
        //! generate private key
        /*! \pre size of privateKey == PrivateKeyLength() */
        virtual void GeneratePrivateKey(RandomNumberGenerator &rng, byte *privateKey) const =0;
        //! generate public key
        /*!     \pre size of publicKey == PublicKeyLength() */
        virtual void GeneratePublicKey(RandomNumberGenerator &rng, const byte *privateKey, byte *publicKey) const =0;
        //! generate private/public key pair
        /*! \note equivalent to calling GeneratePrivateKey() and then GeneratePublicKey() */
        virtual void GenerateKeyPair(RandomNumberGenerator &rng, byte *privateKey, byte *publicKey) const;
        //! derive agreed value from your private key and couterparty's public key, return false in case of failure
        /*! \note If you have previously validated the public key, use validateOtherPublicKey=false to save time.
                \pre size of agreedValue == AgreedValueLength()
                \pre length of privateKey == PrivateKeyLength()
                \pre length of otherPublicKey == PublicKeyLength()
        */
        virtual bool Agree(byte *agreedValue, const byte *privateKey, const byte *otherPublicKey, bool validateOtherPublicKey=true) const =0;

#ifdef CRYPTOPP_MAINTAIN_BACKWARDS_COMPATIBILITY
        bool ValidateDomainParameters(RandomNumberGenerator &rng) const
                {return GetCryptoParameters().Validate(rng, 2);}
#endif
};

//! interface for domains of authenticated key agreement protocols

/*! In an authenticated key agreement protocol, each party has two
        key pairs. The long-lived key pair is called the static key pair,
        and the short-lived key pair is called the ephemeral key pair.
*/
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE AuthenticatedKeyAgreementDomain : public KeyAgreementAlgorithm
{
public:
        //! return length of agreed value produced
        virtual unsigned int AgreedValueLength() const =0;

        //! return length of static private keys in this domain
        virtual unsigned int StaticPrivateKeyLength() const =0;
        //! return length of static public keys in this domain
        virtual unsigned int StaticPublicKeyLength() const =0;
        //! generate static private key
        /*! \pre size of privateKey == PrivateStaticKeyLength() */
        virtual void GenerateStaticPrivateKey(RandomNumberGenerator &rng, byte *privateKey) const =0;
        //! generate static public key
        /*!     \pre size of publicKey == PublicStaticKeyLength() */
        virtual void GenerateStaticPublicKey(RandomNumberGenerator &rng, const byte *privateKey, byte *publicKey) const =0;
        //! generate private/public key pair
        /*! \note equivalent to calling GenerateStaticPrivateKey() and then GenerateStaticPublicKey() */
        virtual void GenerateStaticKeyPair(RandomNumberGenerator &rng, byte *privateKey, byte *publicKey) const;

        //! return length of ephemeral private keys in this domain
        virtual unsigned int EphemeralPrivateKeyLength() const =0;
        //! return length of ephemeral public keys in this domain
        virtual unsigned int EphemeralPublicKeyLength() const =0;
        //! generate ephemeral private key
        /*! \pre size of privateKey == PrivateEphemeralKeyLength() */
        virtual void GenerateEphemeralPrivateKey(RandomNumberGenerator &rng, byte *privateKey) const =0;
        //! generate ephemeral public key
        /*!     \pre size of publicKey == PublicEphemeralKeyLength() */
        virtual void GenerateEphemeralPublicKey(RandomNumberGenerator &rng, const byte *privateKey, byte *publicKey) const =0;
        //! generate private/public key pair
        /*! \note equivalent to calling GenerateEphemeralPrivateKey() and then GenerateEphemeralPublicKey() */
        virtual void GenerateEphemeralKeyPair(RandomNumberGenerator &rng, byte *privateKey, byte *publicKey) const;

        //! derive agreed value from your private keys and couterparty's public keys, return false in case of failure
        /*! \note The ephemeral public key will always be validated.
                      If you have previously validated the static public key, use validateStaticOtherPublicKey=false to save time.
                \pre size of agreedValue == AgreedValueLength()
                \pre length of staticPrivateKey == StaticPrivateKeyLength()
                \pre length of ephemeralPrivateKey == EphemeralPrivateKeyLength()
                \pre length of staticOtherPublicKey == StaticPublicKeyLength()
                \pre length of ephemeralOtherPublicKey == EphemeralPublicKeyLength()
        */
        virtual bool Agree(byte *agreedValue,
                const byte *staticPrivateKey, const byte *ephemeralPrivateKey,
                const byte *staticOtherPublicKey, const byte *ephemeralOtherPublicKey,
                bool validateStaticOtherPublicKey=true) const =0;

#ifdef CRYPTOPP_MAINTAIN_BACKWARDS_COMPATIBILITY
        bool ValidateDomainParameters(RandomNumberGenerator &rng) const
                {return GetCryptoParameters().Validate(rng, 2);}
#endif
};

// interface for password authenticated key agreement protocols, not implemented yet
#if 0
//! interface for protocol sessions
/*! The methods should be called in the following order:

        InitializeSession(rng, parameters);     // or call initialize method in derived class
        while (true)
        {
                if (OutgoingMessageAvailable())
                {
                        length = GetOutgoingMessageLength();
                        GetOutgoingMessage(message);
                        ; // send outgoing message
                }

                if (LastMessageProcessed())
                        break;

                ; // receive incoming message
                ProcessIncomingMessage(message);
        }
        ; // call methods in derived class to obtain result of protocol session
*/
class ProtocolSession
{
public:
        //! exception thrown when an invalid protocol message is processed
        class ProtocolError : public Exception
        {
        public:
                ProtocolError(ErrorType errorType, const std::string &s) : Exception(errorType, s) {}
        };

        //! exception thrown when a function is called unexpectedly
        /*! for example calling ProcessIncomingMessage() when ProcessedLastMessage() == true */
        class UnexpectedMethodCall : public Exception
        {
        public:
                UnexpectedMethodCall(const std::string &s) : Exception(OTHER_ERROR, s) {}
        };

        ProtocolSession() : m_rng(NULL), m_throwOnProtocolError(true), m_validState(false) {}
        virtual ~ProtocolSession() {}

        virtual void InitializeSession(RandomNumberGenerator &rng, const NameValuePairs &parameters) =0;

        bool GetThrowOnProtocolError() const {return m_throwOnProtocolError;}
        void SetThrowOnProtocolError(bool throwOnProtocolError) {m_throwOnProtocolError = throwOnProtocolError;}

        bool HasValidState() const {return m_validState;}

        virtual bool OutgoingMessageAvailable() const =0;
        virtual unsigned int GetOutgoingMessageLength() const =0;
        virtual void GetOutgoingMessage(byte *message) =0;

        virtual bool LastMessageProcessed() const =0;
        virtual void ProcessIncomingMessage(const byte *message, unsigned int messageLength) =0;

protected:
        void HandleProtocolError(Exception::ErrorType errorType, const std::string &s) const;
        void CheckAndHandleInvalidState() const;
        void SetValidState(bool valid) {m_validState = valid;}

        RandomNumberGenerator *m_rng;

private:
        bool m_throwOnProtocolError, m_validState;
};

class KeyAgreementSession : public ProtocolSession
{
public:
        virtual unsigned int GetAgreedValueLength() const =0;
        virtual void GetAgreedValue(byte *agreedValue) const =0;
};

class PasswordAuthenticatedKeyAgreementSession : public KeyAgreementSession
{
public:
        void InitializePasswordAuthenticatedKeyAgreementSession(RandomNumberGenerator &rng, 
                const byte *myId, unsigned int myIdLength, 
                const byte *counterPartyId, unsigned int counterPartyIdLength, 
                const byte *passwordOrVerifier, unsigned int passwordOrVerifierLength);
};

class PasswordAuthenticatedKeyAgreementDomain : public KeyAgreementAlgorithm
{
public:
        //! return whether the domain parameters stored in this object are valid
        virtual bool ValidateDomainParameters(RandomNumberGenerator &rng) const
                {return GetCryptoParameters().Validate(rng, 2);}

        virtual unsigned int GetPasswordVerifierLength(const byte *password, unsigned int passwordLength) const =0;
        virtual void GeneratePasswordVerifier(RandomNumberGenerator &rng, const byte *userId, unsigned int userIdLength, const byte *password, unsigned int passwordLength, byte *verifier) const =0;

        enum RoleFlags {CLIENT=1, SERVER=2, INITIATOR=4, RESPONDER=8};

        virtual bool IsValidRole(unsigned int role) =0;
        virtual PasswordAuthenticatedKeyAgreementSession * CreateProtocolSession(unsigned int role) const =0;
};
#endif

//! BER Decode Exception Class, may be thrown during an ASN1 BER decode operation
class CRYPTOPP_DLL BERDecodeErr : public InvalidArgument
{
public: 
        BERDecodeErr() : InvalidArgument("BER decode error") {}
        BERDecodeErr(const std::string &s) : InvalidArgument(s) {}
};

//! interface for encoding and decoding ASN1 objects
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE ASN1Object
{
public:
        virtual ~ASN1Object() {}
        //! decode this object from a BufferedTransformation, using BER (Basic Encoding Rules)
        virtual void BERDecode(BufferedTransformation &bt) =0;
        //! encode this object into a BufferedTransformation, using DER (Distinguished Encoding Rules)
        virtual void DEREncode(BufferedTransformation &bt) const =0;
        //! encode this object into a BufferedTransformation, using BER
        /*! this may be useful if DEREncode() would be too inefficient */
        virtual void BEREncode(BufferedTransformation &bt) const {DEREncode(bt);}
};

#ifdef CRYPTOPP_MAINTAIN_BACKWARDS_COMPATIBILITY
typedef PK_SignatureScheme PK_SignatureSystem;
typedef SimpleKeyAgreementDomain PK_SimpleKeyAgreementDomain;
typedef AuthenticatedKeyAgreementDomain PK_AuthenticatedKeyAgreementDomain;
#endif

NAMESPACE_END

#endif