Password -Based Encryption (PBE) example code

Encrypting -data with a password and writing it to a file

Supporting -code for this example

-void CPBEExample::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); - - // This is used to create a CPBEncryptor object - CPBEncryptor* encryptor = encryption->NewEncryptLC(); - - // Create a buffer of appropriate size to hold the ciphertext - HBufC8* ciphertextTemp = HBufC8::NewLC(encryptor->MaxFinalOutputLength(aInput.Length())); - TPtr8 ciphertext = ciphertextTemp->Des(); - - // Encrypt the input data into the ciphertext buffer - encryptor->ProcessFinalL(aInput, ciphertext); - - // Store encryption data. This contains details of the encryption used (e.g., - // cipher, key size) as well as things like the salt. This must be stored - // along with the encrypted data, otherwise it is not possible to decrypt it - // again! - writeStream << encryption->EncryptionData(); - - // Store the ciphertext - writeStream << ciphertext; - - // Commit the stream - writeStream.CommitL(); - - // Free memory (writeStream, encryption, encryptor, ciphertextTemp) - CleanupStack::PopAndDestroy(4, &writeStream); - } -

Reading data -from a file and decrypting it

Supporting -code for this example

-HBufC8* CPBEExample::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 file - CPBEncryptionData* encryptionData = CPBEncryptionData::NewLC(readStream); - - // Recreate the CPBEncryptElement object, using the encryption data from the - // file and the user's password. This will leave with KErrBadPassphrase if - // the password is wrong. - CPBEncryptElement* encryption = CPBEncryptElement::NewLC(*encryptionData, aPassword); - - // This is used to create a CPBDecryptor object - CPBDecryptor* decryptor = encryption->NewDecryptLC(); - - // Read the ciphertext - HBufC8* ciphertext = HBufC8::NewLC(readStream, KMaxTInt); - - // Allocate a buffer for the plaintext (this will be returned to the caller) - HBufC8* plaintextBuf = HBufC8::NewLC(decryptor->MaxFinalOutputLength(ciphertext->Length())); - TPtr8 plaintext = plaintextBuf->Des(); - - // Decrypt the data - decryptor->ProcessFinalL(*ciphertext, plaintext); - - // Free memory (readStream, encryptionData, encryption, decryptor, ciphertext, plaintext) - CleanupStack::Pop(plaintextBuf); // don't free this - CleanupStack::PopAndDestroy(5, &readStream); - CleanupStack::PushL(plaintextBuf); - - // Return plaintext to the caller - return plaintextBuf; - } -