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

// This file contains the declarations for the abstract base
// classes that provide a uniform interface to this library.

#ifndef CRYPTOPP_CRYPTLIB_H
#define CRYPTOPP_CRYPTLIB_H

#include "config.h"
#include <exception>
#include <string>

NAMESPACE_BEGIN(CryptoPP)

/// base class for all exceptions thrown by Crypto++
class Exception : public std::exception
{
public:
	explicit Exception(const std::string& s) : m_what(s) {}
	virtual ~Exception() throw() {}
    const char *what() const throw() {return (m_what.c_str());}

private:
	std::string m_what;
};

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


/// abstract base class for block ciphers

/** All classes derived from BlockTransformation are block ciphers
	in ECB mode (for example the DESEncryption class), which are stateless.
	These classes should not be used directly, but only in combination with
	a mode class (see \Ref{CipherMode}).

	Note: BlockTransformation objects may assume that pointers to input and
	output blocks are aligned on 32-bit word boundaries.
*/
class BlockTransformation
{
public:
	///
	virtual ~BlockTransformation() {}

	/// encrypt or decrypt one block in place
	//* Precondition: size of inoutBlock == BlockSize().
	virtual void ProcessBlock(byte *inoutBlock) const =0;

	/// encrypt or decrypt one block, may assume inBlock != outBlock
	//* Precondition: size of inBlock and outBlock == BlockSize().
	virtual void ProcessBlock(const byte *inBlock, byte *outBlock) const =0;

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


/// abstract base class for stream ciphers

class StreamCipher
{
public:
	///
	virtual ~StreamCipher() {}

	/// encrypt or decrypt one byte
	virtual byte ProcessByte(byte input) =0;

	/// encrypt or decrypt an array of bytes of specified length in place
	virtual void ProcessString(byte *inoutString, unsigned int length);
	/// encrypt or decrypt an array of bytes of specified length, may assume inString != outString
	virtual void ProcessString(byte *outString, const byte *inString, unsigned int length);
};

///	abstract base class for random access stream ciphers

class RandomAccessStreamCipher : public virtual StreamCipher
{
public:
	///
	virtual ~RandomAccessStreamCipher() {}
	/*/ specify that the next byte to be processed is at absolute position n
		in the plaintext/ciphertext stream */
	virtual void Seek(unsigned long n) =0;
};

///	abstract base class for random number generators
/** All return values are uniformly distributed over the range specified.
*/
class RandomNumberGenerator
{
public:
	///
	virtual ~RandomNumberGenerator() {}

	/// generate new random byte and return it
	virtual byte GetByte() =0;

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

	/// generate a random 32 bit word in the range min to max, inclusive
	virtual word32 GetLong(word32 a=0, word32 b=0xffffffffL);
	/// generate a random 16 bit word in the range min to max, inclusive
	virtual word16 GetShort(word16 a=0, word16 b=0xffff)
		{return (word16)GetLong(a, b);}

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

/// randomly shuffle the specified array, resulting permutation is uniformly distributed
template <class T> void Shuffle(RandomNumberGenerator &rng, T *array, unsigned int size)
{
	while (--size)
		std::swap(array[size], array[(unsigned int)rng.GetLong(0, size)]);
}

/// abstract base class for hash functions
/** HashModule 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 HashModule
{
public:
	///
	virtual ~HashModule() {}

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

	/*/ calculate hash for the current message (the concatenation of all 
		inputs passed in via Update()), then reinitialize the object */
	//* Precondition: size of digest == DigestSize().
	virtual void Final(byte *digest) =0;

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

	/// use this if your input is short and you don't want to call Update() and Final() seperately
	virtual void CalculateDigest(byte *digest, const byte *input, int length)
		{Update(input, length); Final(digest);}
};

/// abstract base class for message authentication codes

/** The main differences between a MAC and an hash function (in terms of
	programmatic interface) is that a MAC is keyed, and that calculating
	a MAC for the same message twice may produce two different results so
	verifying a MAC may not be simply recalculating it and doing a bitwise
	comparison.
*/
class MessageAuthenticationCode : public virtual HashModule
{
public:
	///
	virtual ~MessageAuthenticationCode() {}

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

	/// use this if your input is short and you don't want to call Update() and Verify() seperately
	virtual bool VerifyMAC(const byte *mac, const byte *input, int length)
		{Update(input, length); return Verify(mac);}
};

/// abstract base class for buffered transformations

/** BufferedTransformation is a generalization of \Ref{BlockTransformation},
	\Ref{StreamCipher}, and \Ref{HashModule}.

	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.
	
	Computation is generally done as soon as possible, but some buffering
	on the input may be done for performance reasons.
*/
class BufferedTransformation
{
public:
	///
	virtual ~BufferedTransformation() {}

	//@Man: INPUT
	//@{
		/// input a byte for processing
		virtual void Put(byte inByte) =0;
		/// input multiple bytes
		virtual void Put(const byte *inString, unsigned int length) =0;
		/// signal that no more input is available
		virtual void InputFinished() {}

		/// input a 16-bit word, big-endian or little-endian depending on highFirst
		void PutShort(word16 value, bool highFirst=true);
		/// input a 32-bit word
		void PutLong(word32 value, bool highFirst=true);
	//@}

	//@Man: RETRIEVAL
	//@{
		/// 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
			MaxRetrieveable(). */
		virtual unsigned long MaxRetrieveable() =0;

		/// try to retrieve a single byte
		virtual unsigned int Get(byte &outByte) =0;
		/// try to retrieve multiple bytes
		virtual unsigned int Get(byte *outString, unsigned int getMax) =0;

		/// try to retrieve a 16-bit word, big-endian or little-endian depending on highFirst
		int GetShort(word16 &value, bool highFirst=true);
		/// try to retrieve a 32-bit word
		int GetLong(word32 &value, bool highFirst=true);

		/// move all of the buffered output to target as input
		virtual void TransferTo(BufferedTransformation &target);
		/// same as above but only transfer up to transferMax bytes
		virtual unsigned int TransferTo(BufferedTransformation &target, unsigned int transferMax);

		/// peek at the next byte without removing it from the output buffer
		virtual unsigned int Peek(byte &outByte) const =0;

		/// discard some bytes from the output buffer
		unsigned int Skip(unsigned int skipMax);
	//@}

	//@Man: ATTACHMENT
	//@{
		/** Some BufferedTransformation objects (e.g. \Ref{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.  See the
			documentation for the \Ref{Filter} class for the details.
		*/
		///
		virtual bool Attachable() {return false;}
		///
		virtual void Detach(BufferedTransformation *p = 0) {}	// NULL is undefined at this point
		///
		virtual void Attach(BufferedTransformation *) {}
		/// call InputFinished() for all attached objects
		virtual void Close() {InputFinished();}
	//@}
};

/// abstract base class for public-key encryptors and decryptors

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

	/// maximum length of plaintext for a given ciphertext length
	//* This function returns 0 if cipherTextLength is not valid (too long or too short).
	virtual unsigned int MaxPlainTextLength(unsigned int cipherTextLength) const =0;

	/// calculate length of ciphertext given length of plaintext
	//* This function returns 0 if plainTextLength is not valid (too long).
	virtual unsigned int CipherTextLength(unsigned int plainTextLength) const =0;
};

///	abstract base class for public-key encryptors

/** An encryptor is also a public encryption key.  It contains both the
	key and the algorithm to perform the encryption.
*/
class PK_Encryptor : public virtual PK_CryptoSystem
{
public:
	/// encrypt a byte string
	/** Preconditions:
			\begin{itemize} 
			\item CipherTextLength(plainTextLength) != 0 (i.e., plainText isn't too long)
			\item size of cipherText == CipherTextLength(plainTextLength)
			\end{itemize}
	*/
	virtual void Encrypt(RandomNumberGenerator &rng, const byte *plainText, unsigned int plainTextLength, byte *cipherText) =0;
};

///	abstract base class for public-key decryptors

/** An decryptor is also a private decryption key.  It contains both the
	key and the algorithm to perform the decryption.
*/
class PK_Decryptor : public virtual PK_CryptoSystem
{
public:
	/// decrypt a byte string, and return the length of plaintext
	/** Precondition: size of plainText == MaxPlainTextLength(cipherTextLength)
		bytes.  
		
		The function returns the actual length of the plaintext, or 0
		if decryption fails.
	*/