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

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

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

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

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

<!-- Initial Contributors:

    Nokia Corporation - initial contribution.

Contributors: 

-->

<!DOCTYPE concept

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

<concept xml:lang="en" id="GUID-598B6698-3518-50CA-98DE-D85CB255BA2D"><title>Secure stream encryption example code</title><prolog><metadata><keywords/></metadata></prolog><conbody><p>This example covers: </p> <ul><li id="GUID-3F36B509-4E9F-5F4C-A374-993714418DEF"><p> <xref href="GUID-598B6698-3518-50CA-98DE-D85CB255BA2D.dita#GUID-598B6698-3518-50CA-98DE-D85CB255BA2D/GUID-C27DAD65-463E-5CC6-A7D1-58F5DB3F279E">Encrypting some data with a password and writing it to a file</xref>  </p> </li> <li id="GUID-BE3A3FB7-E5C6-5488-800A-6BDBCD693C99"><p> <xref href="GUID-598B6698-3518-50CA-98DE-D85CB255BA2D.dita#GUID-598B6698-3518-50CA-98DE-D85CB255BA2D/GUID-75B9241A-82D2-52F1-BDCE-B8E329F72BDE">Reading the data back from the file and decrypting it with the same password.</xref>  </p> </li> </ul> <p>Also, see: </p> <ul><li id="GUID-B8CC38F9-AAD9-5FCF-BE9E-F0526443AEFC"><p> <xref href="GUID-3385079E-84F4-534F-B937-BD3A568D71BC.dita">PBE example code</xref>  </p> </li> <li id="GUID-9952F1C6-982E-54EE-B8E2-29B99141106B"><p> <xref href="GUID-36BCDD1F-3713-5DF0-8D8A-CF093694B636.dita">Secure store example code</xref>  </p> </li> </ul> <section id="GUID-C27DAD65-463E-5CC6-A7D1-58F5DB3F279E"><title>Encrypting data with a password and writing it to a file</title> <ul><li id="GUID-0CF095D9-2387-5DAA-B599-9255C142D5AB"><p> <xref href="GUID-267D1E20-002E-53C7-8AE5-E063206C1562.dita">Supporting code for this example</xref>  </p> </li> </ul> <codeblock id="GUID-D41E94E7-F29F-57F4-9DC2-5BFE018BC7C8" xml:space="preserve">

void CSecureStreamExample::WriteEncryptedDataL(const TDesC8& aInput, const TDesC& aFilename, const TDesC& aPassword)

         {

         // Open a stream to the output file

         RFileWriteStream writeStream;

         User::LeaveIfError(writeStream.Replace(iFs, aFilename, EFileShareExclusive | EFileWrite));

         CleanupClosePushL(writeStream);

         // Create a CPBEncryptElement object, passing details of the encryption we

         // are using and the user's password

         CPBEncryptElement* encryption = CPBEncryptElement::NewLC(aPassword, ECipherDES_CBC);

         // Store encryption data as the first thing in the stream

         writeStream << encryption->EncryptionData();

         // Create an REncryptStream - this wraps the write stream and encrypts

         // everything written to it

         REncryptStream encStream;

         encStream.OpenL(writeStream, *encryption);

         CleanupClosePushL(encStream);

         // Now we can simply write the plaintext to the encrypt stream - it gets

         // encrypted automatically

         encStream << aInput;

         // Commit the stream

         encStream.CommitL();

         // Free memory (writeStream, encryption, encStream)

         CleanupStack::PopAndDestroy(3, &writeStream);

         }

            </codeblock> </section> <section id="GUID-75B9241A-82D2-52F1-BDCE-B8E329F72BDE"><title>Reading data from a file and decrypting it</title> <ul><li id="GUID-952B8F2D-DBA3-5338-BC7D-CA835EA9BA29"><p> <xref href="GUID-267D1E20-002E-53C7-8AE5-E063206C1562.dita">Supporting code for this example</xref>  </p> </li> </ul> <codeblock id="GUID-93A9C97B-E085-5171-A524-2E34BF726000" xml:space="preserve">

HBufC8* CSecureStreamExample::ReadEncryptedDataLC(const TDesC& aFilename, const TDesC& aPassword)

         {

         // Open a stream to the input file

         RFileReadStream readStream;

         User::LeaveIfError(readStream.Open(iFs, aFilename, EFileRead));

         CleanupClosePushL(readStream);

         // Read the encryption data from the stream

         CPBEncryptionData* encryptionData = CPBEncryptionData::NewLC(readStream);

         // Recreate the CPBEncryptElement object, using the encryption data from the

         // file and the user's password

         CPBEncryptElement* encryption = CPBEncryptElement::NewLC(*encryptionData, aPassword);

         // Create an RDecryptStream based on the read stream - this decrypts

         // everything we read from it

         RDecryptStream decStream;

         decStream.OpenL(readStream, *encryption);

         CleanupClosePushL(decStream);

         // Now we can read the plaintext straight from the stream

         HBufC8* plaintext = HBufC8::NewL(decStream, KMaxTInt);

         // Free memory (readStream, encryptionData, encryption, decStream)

         CleanupStack::PopAndDestroy(4, &readStream);

         CleanupStack::PushL(plaintext);

         // Return plaintext to the caller

         return plaintext;

         }

        </codeblock> </section> </conbody></concept>