public async Task DecryptFileAes(FileItemViewModel fileToDecrypt)
{
if (fileToDecrypt.IsEncrypted)
{
var serializer = new XmlSerializer(typeof(SerialisableAuthData));
SerialisableAuthData tagData = null;
using (var stream = await fileToDecrypt.File.OpenStreamForReadAsync())
{
tagData = serializer.Deserialize(stream) as SerialisableAuthData;
stream.Dispose();
}
if (tagData != null)
{
var data = tagData.GetData();
var tag = tagData.GetTag();
var decryptedData = CryptographicEngine.DecryptAndAuthenticate(aesKey, data,
fileToDecrypt.Nonce, tag, null);
await FileIO.WriteBufferAsync(fileToDecrypt.File, decryptedData);
}
fileToDecrypt.IsEncrypted = false;
}
else
{
throw new Exception("Tried to dencrypt file with encrypted flag already set to false");
}
}
//String strMsg = "1234567812345678"; // Data to encrypt.
//String strAlgName = SymmetricAlgorithmNames.AesCbc;
//UInt32 keyLength = 32; // Length of the key, in bytes
//BinaryStringEncoding encoding; // Binary encoding value
//IBuffer iv; // Initialization vector
//CryptographicKey key;
public async Task EncryptFileAes(FileItemViewModel fileToEncrypt)
{
if (!fileToEncrypt.IsEncrypted)
{
var fileBuffer = await FileIO.ReadBufferAsync(fileToEncrypt.File);
CreateNonce(fileToEncrypt);
var encryptedData = CryptographicEngine.EncryptAndAuthenticate(aesKey, fileBuffer, fileToEncrypt.Nonce,
null);
var serialData = new SerialisableAuthData(encryptedData.AuthenticationTag, encryptedData.EncryptedData);
var serializer = new XmlSerializer(typeof(SerialisableAuthData));
using (var stream = await fileToEncrypt.File.OpenStreamForWriteAsync())
{
TextWriter output = new StreamWriter(stream);
serializer.Serialize(output, serialData);
await stream.FlushAsync();
output.Dispose();
stream.Dispose();
}
fileToEncrypt.IsEncrypted = true;
}
else
{
throw new Exception("Tried to encrypt file with encrypted flag already set to true");
}
}