Symaptic: os/security/crypto/weakcrypto/inc/arc4.h@bde4ae8d615e

     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 */

    22 /**

    23  @file

    24  @publishedPartner

    25  @released

    26 */

    28 #ifndef __ARC4_H__

    29 #define __ARC4_H__

    31 #include "streamcipher.h"

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

    34 const TInt KSBoxSize = 256;

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

    37 const TInt KMaxARC4KeyBytes = 256; //2048 bits

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

    40 const TUint KDefaultDiscardBytes = 768;

    42 /**

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

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

    45 *

    46 */

    47 class CARC4 : public CStreamCipher

    48 {

    49 public:

    50 	/**

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

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

    53 	*

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

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

    56 	*

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

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

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

    60 	*		KDefaultDiscardBytes bytes of the key stream.

    61 	*

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

    63 	*						KRC4MaxKeySizeBytes.

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

    65 	*						stream.

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

    67 	*

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

    69 	*								cipher strength restrictions of the crypto library.

    70 	*								See TCrypto::IsSymmetricWeakEnoughL()

    71 	*/

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

    73 		TUint aDiscardBytes = KDefaultDiscardBytes);

    75 	/**

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

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

    78 	*

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

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

    81 	*

    82 	* @see CARC4::NewL()

    83 	*

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

    85 	*						KRC4MaxKeySizeBytes.

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

    87 	*						stream.

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

    89 	*

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

    91 	*								cipher strength restrictions of the crypto library.

    92 	*								See TCrypto::IsSymmetricWeakEnoughL()

    93 	*/

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

    95 		TUint aDiscardBytes = KDefaultDiscardBytes);

    96 public:

    97 	virtual void Reset(void);

    98 	virtual TInt KeySize(void) const;

    99 protected:

   100 	/**

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

   102 	 *

   103 	 * @note ARC4 encryption and decryption are symmetrical.

   104 	 *

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

   106 	 *				on return, transformed data.

   107 	 */

   108 	virtual void DoProcess(TDes8& aData);

   109 private:

   110 	CARC4(const TDesC8& aKey, TUint aDiscardBytes);

   111 	void GenerateSBox();

   112 	inline TUint8 GenerateByte();

   113 	void DiscardBytes(TInt aDiscardBytes);

   114 private:

   115 	TUint8 ix;

   116 	TUint8 iy;

   117 	TInt iDiscardBytes;

   118 	TUint8 iState[KSBoxSize];

   119 	TBuf8<KMaxARC4KeyBytes> iKey;

   120 };

   122 #endif	//	__ARC4_H__

author	sl@SLION-WIN7.fritz.box
	Fri, 15 Jun 2012 03:10:57 +0200
changeset 0	bde4ae8d615e
permissions	-rw-r--r--