1 /*

     2 * Copyright (c) 2002-2009 Nokia Corporation and/or its subsidiary(-ies).

     3 * All rights reserved.

     4 * This component and the accompanying materials are made available

     5 * under the terms of the License "Eclipse Public License v1.0"

     6 * which accompanies this distribution, and is available

     7 * at the URL "http://www.eclipse.org/legal/epl-v10.html".

     8 *

     9 * Initial Contributors:

    10 * Nokia Corporation - initial contribution.

    11 *

    12 * Contributors:

    13 *

    14 * Description: 

    15 * ** IMPORTANT ** PublishedPartner API's in this file are published to 3rd party developers via the 

    16 * Symbian website. Changes to these API's should be treated as PublishedAll API changes and the Security TA should be consulted.

    17 * RC4 implementation

    18 *

    19 */

    20 

    21 

    22 /**

    23  @file 

    24  @publishedPartner

    25  @released 

    26 */

    27  

    28 #ifndef __ARC4_H__

    29 #define __ARC4_H__

    30 

    31 #include <streamcipher.h>

    32 

    33 #ifndef SYMBIAN_ENABLE_SPLIT_HEADERS

    34 /** The size of the substitution box (i.e. lookup table) in bytes. */

    35 const TInt KSBoxSize = 256;

    36 #endif

    37 

    38 /** Maximum ARC4 key size in bytes. */

    39 const TInt KMaxARC4KeyBytes = 256; //2048 bits

    40 

    41 /** Number of bytes to discard by default from an ARC4 key stream. */

    42 const TUint KDefaultDiscardBytes = 768;

    43 

    44 /**

    45 * Implements an RC4-compatible stream cipher that outputs a pseudorandom stream

    46 * of bits, having been initialised with a key. 

    47 *

    48 */

    49 class CARC4 : public CStreamCipher

    50 {

    51 public:

    52 	/**

    53 	* Constructs an instance of a CARC4 object, and initialises it with a key and

    54 	* (optionally) the number of initial bytes to discard. Defaults to 256. 

    55 	*

    56 	* The number of dropped bytes <b>must</b> be agreed with the other

    57 	* party, with which information is to be exchanged, prior to encipherment.

    58 	*

    59 	* @note	Several papers have been published indicating that there are weaknesses 

    60 	*		in the first bytes of an ARC4 byte stream.  A search for "ARC4

    61 	*		discard" should find these papers.  Recommended practice is to drop the first

    62 	*		KDefaultDiscardBytes bytes of the key stream.  

    63 	*

    64 	* @param aKey			The key to use.  aKey must be less than or equal to

    65 	*						KRC4MaxKeySizeBytes.  

    66 	* @param aDiscardBytes	The number of bytes to drop from the beginning of the key

    67 	*						stream.

    68 	* @return				A pointer to the new CARC4 object.

    69 	*  

    70 	* @leave KErrKeyNotWeakEnough	If the key size is larger than that allowed by the

    71 	*								cipher strength restrictions of the crypto library.

    72 	*								See TCrypto::IsSymmetricWeakEnoughL()

    73 	*/

    74 	IMPORT_C static CARC4* NewL(const TDesC8& aKey, 

    75 		TUint aDiscardBytes = KDefaultDiscardBytes);

    76 

    77 	/**

    78 	* Constructs an instance of a CARC4 object, and initialises it with a key and

    79 	* (optionally) the number of initial bytes to discard. Defaults to 256. 

    80 	*

    81 	* The number of dropped bytes <b>must</b> be agreed with the other

    82 	* party, with which information is to be exchanged, prior to encipherment.

    83 	*

    84 	* @see CARC4::NewL()

    85 	*

    86 	* @param aKey			The key to use.  aKey must be less than or equal to

    87 	*						KRC4MaxKeySizeBytes.  

    88 	* @param aDiscardBytes	The number of bytes to drop from the beginning of the key

    89 	*						stream.

    90 	* @return				A pointer to the new CARC4 object.

    91 	*  

    92 	* @leave KErrKeyNotWeakEnough	If the key size is larger than that allowed by the

    93 	*								cipher strength restrictions of the crypto library.

    94 	*								See TCrypto::IsSymmetricWeakEnoughL()

    95 	*/

    96 	IMPORT_C static CARC4* NewLC(const TDesC8& aKey, 

    97 		TUint aDiscardBytes = KDefaultDiscardBytes);

    98 public:	

    99 	virtual void Reset(void);

   100 	virtual TInt KeySize(void) const;

   101 protected:

   102 	/**	

   103 	 * Performs an ARC4 encryption or decryption on supplied data.

   104 	 * 

   105 	 * @note ARC4 encryption and decryption are symmetrical.

   106 	 *

   107 	 * @param aData	On input, data to be transformed; 

   108 	 *				on return, transformed data.

   109 	 */

   110 	virtual void DoProcess(TDes8& aData);

   111 	/** @internalComponent */

   112 	CARC4();

   113 };

   114 

   115 #endif	//	__ARC4_H__