sl@0: /*
sl@0: * Copyright (c) 2002-2009 Nokia Corporation and/or its subsidiary(-ies).
sl@0: * All rights reserved.
sl@0: * This component and the accompanying materials are made available
sl@0: * under the terms of the License "Eclipse Public License v1.0"
sl@0: * which accompanies this distribution, and is available
sl@0: * at the URL "http://www.eclipse.org/legal/epl-v10.html".
sl@0: *
sl@0: * Initial Contributors:
sl@0: * Nokia Corporation - initial contribution.
sl@0: *
sl@0: * Contributors:
sl@0: *
sl@0: * Description: 
sl@0: * ** IMPORTANT ** PublishedPartner API's in this file are published to 3rd party developers via the 
sl@0: * Symbian website. Changes to these API's should be treated as PublishedAll API changes and the Security TA should be consulted.
sl@0: * RC4 implementation
sl@0: *
sl@0: */
sl@0: 
sl@0: 
sl@0: /**
sl@0:  @file 
sl@0:  @publishedPartner
sl@0:  @released 
sl@0: */
sl@0:  
sl@0: #ifndef __ARC4_H__
sl@0: #define __ARC4_H__
sl@0: 
sl@0: #include "streamcipher.h"
sl@0: 
sl@0: /** The size of the substitution box (i.e. lookup table) in bytes. */
sl@0: const TInt KSBoxSize = 256;
sl@0: 
sl@0: /** Maximum ARC4 key size in bytes. */
sl@0: const TInt KMaxARC4KeyBytes = 256; //2048 bits
sl@0: 
sl@0: /** Number of bytes to discard by default from an ARC4 key stream. */
sl@0: const TUint KDefaultDiscardBytes = 768;
sl@0: 
sl@0: /**
sl@0: * Implements an RC4-compatible stream cipher that outputs a pseudorandom stream
sl@0: * of bits, having been initialised with a key. 
sl@0: *
sl@0: */
sl@0: class CARC4 : public CStreamCipher
sl@0: {
sl@0: public:
sl@0: 	/**
sl@0: 	* Constructs an instance of a CARC4 object, and initialises it with a key and
sl@0: 	* (optionally) the number of initial bytes to discard. Defaults to 256. 
sl@0: 	*
sl@0: 	* The number of dropped bytes <b>must</b> be agreed with the other
sl@0: 	* party, with which information is to be exchanged, prior to encipherment.
sl@0: 	*
sl@0: 	* @note	Several papers have been published indicating that there are weaknesses 
sl@0: 	*		in the first bytes of an ARC4 byte stream.  A search for "ARC4
sl@0: 	*		discard" should find these papers.  Recommended practice is to drop the first
sl@0: 	*		KDefaultDiscardBytes bytes of the key stream.  
sl@0: 	*
sl@0: 	* @param aKey			The key to use.  aKey must be less than or equal to
sl@0: 	*						KRC4MaxKeySizeBytes.  
sl@0: 	* @param aDiscardBytes	The number of bytes to drop from the beginning of the key
sl@0: 	*						stream.
sl@0: 	* @return				A pointer to the new CARC4 object.
sl@0: 	*  
sl@0: 	* @leave KErrKeyNotWeakEnough	If the key size is larger than that allowed by the
sl@0: 	*								cipher strength restrictions of the crypto library.
sl@0: 	*								See TCrypto::IsSymmetricWeakEnoughL()
sl@0: 	*/
sl@0: 	IMPORT_C static CARC4* NewL(const TDesC8& aKey, 
sl@0: 		TUint aDiscardBytes = KDefaultDiscardBytes);
sl@0: 
sl@0: 	/**
sl@0: 	* Constructs an instance of a CARC4 object, and initialises it with a key and
sl@0: 	* (optionally) the number of initial bytes to discard. Defaults to 256. 
sl@0: 	*
sl@0: 	* The number of dropped bytes <b>must</b> be agreed with the other
sl@0: 	* party, with which information is to be exchanged, prior to encipherment.
sl@0: 	*
sl@0: 	* @see CARC4::NewL()
sl@0: 	*
sl@0: 	* @param aKey			The key to use.  aKey must be less than or equal to
sl@0: 	*						KRC4MaxKeySizeBytes.  
sl@0: 	* @param aDiscardBytes	The number of bytes to drop from the beginning of the key
sl@0: 	*						stream.
sl@0: 	* @return				A pointer to the new CARC4 object.
sl@0: 	*  
sl@0: 	* @leave KErrKeyNotWeakEnough	If the key size is larger than that allowed by the
sl@0: 	*								cipher strength restrictions of the crypto library.
sl@0: 	*								See TCrypto::IsSymmetricWeakEnoughL()
sl@0: 	*/
sl@0: 	IMPORT_C static CARC4* NewLC(const TDesC8& aKey, 
sl@0: 		TUint aDiscardBytes = KDefaultDiscardBytes);
sl@0: public:	
sl@0: 	virtual void Reset(void);
sl@0: 	virtual TInt KeySize(void) const;
sl@0: protected:
sl@0: 	/**	
sl@0: 	 * Performs an ARC4 encryption or decryption on supplied data.
sl@0: 	 * 
sl@0: 	 * @note ARC4 encryption and decryption are symmetrical.
sl@0: 	 *
sl@0: 	 * @param aData	On input, data to be transformed; 
sl@0: 	 *				on return, transformed data.
sl@0: 	 */
sl@0: 	virtual void DoProcess(TDes8& aData);
sl@0: private:
sl@0: 	CARC4(const TDesC8& aKey, TUint aDiscardBytes);
sl@0: 	void GenerateSBox();
sl@0: 	inline TUint8 GenerateByte();
sl@0: 	void DiscardBytes(TInt aDiscardBytes);
sl@0: private:
sl@0: 	TUint8 ix;
sl@0: 	TUint8 iy;
sl@0: 	TInt iDiscardBytes;
sl@0: 	TUint8 iState[KSBoxSize];
sl@0: 	TBuf8<KMaxARC4KeyBytes> iKey;
sl@0: };
sl@0: 
sl@0: #endif	//	__ARC4_H__