1 <?xml version="1.0" encoding="utf-8"?>

     2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->

     3 <!-- This component and the accompanying materials are made available under the terms of the License 

     4 "Eclipse Public License v1.0" which accompanies this distribution, 

     5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->

     6 <!-- Initial Contributors:

     7     Nokia Corporation - initial contribution.

     8 Contributors: 

     9 -->

    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-D2D17EF9-FFC6-5FBD-A992-55746A12B625" xml:lang="en"><title>Basic

    13 encryption and decryption using a symmetric cipher</title><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 <p>This example demonstrates how to encrypt and decrypt a small string of

    15 data using a symmetric cipher. Firstly, an encryption operation is performed

    16 on the data. Following this a decryption operation is performed on the encrypted

    17 data. Finally a check is made on the decrypted data for equality with the

    18 original data which tests that the encrypt and decrypt operations have maintained

    19 data integrity. </p>

    20 <codeblock id="GUID-E9342EBD-213A-53CE-BA3E-93CC24D63319" xml:space="preserve">#include &lt;legacyselector.h&gt;

    21 #include <cryptosymmetriccipherapi.h>

    22 #include <keys.h>

    23 

    24 using namespace CryptoSpi;

    25 

    26 //Create a new CCryptoParams object to encapsulate the secret key string and key type

    27 CCryptoParams* params = CCryptoParams::NewLC(); 

    28 

    29 //Add the secret key to the CCryptoParams object by calling the CCryptoParams::AddL() method,  

    30 //passing in the key string and appropriate key parameter UID

    31 params->AddL( _L8("12345678"), KSymmetricKeyParameterUid);

    32 

    33 //Create a key object (CKey) by passing in an instance of TKeyProperty and the previously 

    34 //created CCryptoParams object containing the secret key. 

    35 TKeyProperty keyProperty = {KDesUid, KNullUid, KSymmetricKey, KNonEmbeddedKeyUid};

    36 CKey* key=CKey::NewL(keyProperty, *params); 

    37 CleanupStack::PushL(key);

    38 //Create and initialize a pointer for the Symmetric cipher implementation object

    39 CSymmetricCipher* impl = NULL;    

    40 

    41 //Create a symmetric cipher passing in the appropriate CKey object

    42 TRAPD(err, CSymmetricCipherFactory::CreateSymmetricCipherL

    43     (impl,

    44     KDesUid,

    45     *key,

    46     KCryptoModeEncryptUid,  // This can be either encrypt or decrypt

    47     KOperationModeECBUid,   // Use "electronic code book" mode

    48     KPaddingModeNoneUid,   // This is the type of padding to be used

    49     NULL));

    50 

    51 //Check the return value and for non NULL

    52 if (impl && (err == KErrNone))

    53     {

    54     //Create a buffer holding the data to be encrypted

    55     TBuf8<8> srcData(_L8("12345678"));

    56     

    57     //Create a buffer to hold the encrypted data.

    58     //MaxFinalOutputLength() returns the number of bytes the buffer passed to ProcessFinalL()

    59     //needs to be capable of holding

    60     TInt maxOutputLength = impl->MaxFinalOutputLength(srcData.Length());

    61     HBufC8* encrypted =    HBufC8::NewLC(maxOutputLength);

    62     TPtr8 encryptedPtr = encrypted->Des();

    63 

    64     //Perform the encryption operation 

    65     //ProcessFinalL() pads the input buffer if required

    66     TRAP(err, impl->ProcessFinalL(srcData, encryptedPtr));

    67 

    68     if (err == KErrNone)

    69         {

    70         //Switch to decrypt mode

    71         impl->SetCryptoModeL(KCryptoModeDecryptUid);

    72     

    73         //Create a buffer for the decrypted data

    74         maxOutputLength = encryptedPtr.Length();

    75         HBufC8* output = HBufC8::NewLC(impl->MaxFinalOutputLength(maxOutputLength));

    76         TPtr8 outputPtr = output->Des();

    77         

    78         //Perform the decryption operation

    79         TRAP(err, impl->ProcessFinalL(encryptedPtr, outputPtr));

    80 

    81     if (err == KErrNone)

    82         {

    83             //Check that the original source data matches the data that 

    84             //has been encrypted then decrypted

    85             if (!outputPtr.Compare(srcData))

    86                 {

    87                 // Descriptors are the same - successful encrypt/decrypt check

    88                 }

    89             }

    90 

    91         CleanupStack::PopAndDestroy(output); 

    92         }

    93 

    94     CleanupStack::PopAndDestroy(encrypted); 

    95     }

    96 

    97 //Destroy the symmetric implementation object    

    98 delete impl;

    99 impl = NULL;

   100 

   101 CleanupStack::PopAndDestroy(key);

   102 CleanupStack::PopAndDestroy(params);</codeblock>

   103 </conbody></concept>