1 /**

     2 @page pbe_example_code PBE example code

     3 	

     4 	This example covers: 

     5 		-# @ref pbe_example_1 "Encrypting some data with a password and writing it to a file"

     6 		-# @ref pbe_example_2 "Reading the data back from the file and decrypting it with the same password".

     7 

     8 	<i>This example code is really for reference only - it would be better to use:</i>

     9 		- @ref secure_stream_example_code

    10 		- @ref secure_store_example_code	

    11 

    12 <hr>

    13 

    14 	- @ref pbe_example_code_support "Supporting code for this example".

    15 

    16 @anchor pbe_example_1

    17 @code

    18 /*

    19  * Encrypt data with password and write it to a file.

    20  */

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

    22 		 {

    23 		 // Open a stream to the output file

    24 		 RFileWriteStream writeStream;

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

    26 		 CleanupClosePushL(writeStream);

    27 

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

    29 		 // are using and the user's password

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

    31 

    32 		 // This is used to create a CPBEncryptor object

    33 		 CPBEncryptor* encryptor = encryption->NewEncryptLC();

    34 

    35 		 // Create a buffer of appropriate size to hold the ciphertext

    36 		 HBufC8* ciphertextTemp = HBufC8::NewLC(encryptor->MaxFinalOutputLength(aInput.Length()));

    37 		 TPtr8 ciphertext = ciphertextTemp->Des();		 

    38 

    39 		 // Encrypt the input data into the ciphertext buffer

    40 		 encryptor->ProcessFinalL(aInput, ciphertext);

    41 

    42 		 // Store encryption data.  This contains details of the encryption used (e.g.,

    43 		 // cipher, key size) as well as things like the salt.  This must be stored

    44 		 // along with the encrypted data, otherwise it is not possible to decrypt it

    45 		 // again!

    46 		 writeStream << encryption->EncryptionData();

    47 

    48 		 // Store the ciphertext

    49 		 writeStream << ciphertext;

    50 

    51 		 // Commit the stream

    52 		 writeStream.CommitL();

    53 

    54 		 // Free memory (writeStream, encryption, encryptor, ciphertextTemp)

    55 		 CleanupStack::PopAndDestroy(4, &writeStream);

    56 		 }

    57 @endcode

    58 

    59 @anchor pbe_example_2

    60 @code

    61 /*

    62  * Read data from file and decrypt it.

    63  */

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

    65 		 {

    66 		 // Open a stream to the input file

    67 		 RFileReadStream readStream;

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

    69 		 CleanupClosePushL(readStream);

    70 

    71 		 // Read the encryption data from the file

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

    73 		 

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

    75 		 // file and the user's password.  This will leave with KErrBadPassphrase if

    76 		 // the password is wrong.

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

    78 

    79 		 // This is used to create a CPBDecryptor object

    80 		 CPBDecryptor* decryptor = encryption->NewDecryptLC();

    81 		 

    82 		 // Read the ciphertext

    83 		 HBufC8* ciphertext = HBufC8::NewLC(readStream, KMaxTInt);

    84 

    85 		 // Allocate a buffer for the plaintext (this will be returned to the caller)

    86 		 HBufC8* plaintextBuf = HBufC8::NewLC(decryptor->MaxFinalOutputLength(ciphertext->Length()));

    87 		 TPtr8 plaintext = plaintextBuf->Des();

    88 

    89 		 // Decrypt the data

    90 		 decryptor->ProcessFinalL(*ciphertext, plaintext);

    91 

    92 		 // Free memory (readStream, encryptionData, encryption, decryptor, ciphertext, plaintext)

    93 		 CleanupStack::Pop(plaintextBuf); // don't free this

    94 		 CleanupStack::PopAndDestroy(5, &readStream);

    95 		 CleanupStack::PushL(plaintextBuf);

    96 

    97 		 // Return plaintext to the caller

    98 		 return plaintextBuf;

    99 		 }

   100 

   101 @endcode

   102 

   103 */