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

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     7     Nokia Corporation - initial contribution.

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    10 <!DOCTYPE concept

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

    12 <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">

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

    14          {

    15          // Open a stream to the output file

    16          RFileWriteStream writeStream;

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

    18          CleanupClosePushL(writeStream);

    19                 

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

    21          // are using and the user's password

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

    23                 

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

    25          writeStream << encryption->EncryptionData();

    26                 

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

    28          // everything written to it

    29          REncryptStream encStream;

    30          encStream.OpenL(writeStream, *encryption);

    31          CleanupClosePushL(encStream);

    32                 

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

    34          // encrypted automatically

    35          encStream << aInput;

    36                 

    37          // Commit the stream

    38          encStream.CommitL();

    39                 

    40          // Free memory (writeStream, encryption, encStream)

    41          CleanupStack::PopAndDestroy(3, &writeStream);

    42          }

    43             </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">

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

    45          {

    46          // Open a stream to the input file

    47          RFileReadStream readStream;

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

    49          CleanupClosePushL(readStream);

    50 

    51          // Read the encryption data from the stream

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

    53          

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

    55          // file and the user's password

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

    57 

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

    59          // everything we read from it

    60          RDecryptStream decStream;

    61          decStream.OpenL(readStream, *encryption);

    62          CleanupClosePushL(decStream);

    63     

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

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

    66              

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

    68          CleanupStack::PopAndDestroy(4, &readStream);

    69          CleanupStack::PushL(plaintext);

    70     

    71          // Return plaintext to the caller

    72          return plaintext;

    73          }

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