internal byte[] DecryptFileExplicit(byte[] encryptedBytes, CryptoChoice settings)
{
byte[] fileBytes;
switch (settings.Choice)
{
case CryptoChoices.OneTimePad:
OneTimePadCrypter otp = new OneTimePadCrypter(settings.Key);
fileBytes = otp.Decrypt(encryptedBytes);
break;
case CryptoChoices.TEA:
TEACrypter tea = new TEACrypter(settings.Key);
fileBytes = tea.Decrypt(encryptedBytes);
if (settings.Depad)
{
fileBytes = TEACrypter.DepadData(fileBytes);
}
break;
default:
throw new InvalidOperationException("Cryption settings are not valid: Desired cryption algorithm doesn't exist.");
}
return(fileBytes);
}
private byte[] DecryptDataFile(byte[] encryptedBytes)
{
byte[] fileBytes;
switch (Settings.Default.DataFileCryption)
{
case CryptoChoices.OneTimePad:
OneTimePadCrypter otp = new OneTimePadCrypter(Encoding.UTF8.GetBytes(Settings.Default.CryptionDataKey));
fileBytes = otp.Decrypt(encryptedBytes);
break;
case CryptoChoices.TEA:
TEACrypter tea = new TEACrypter(Encoding.UTF8.GetBytes(Settings.Default.CryptionDataKey));
fileBytes = tea.Decrypt(encryptedBytes);
if (Settings.Default.DataFilePadded)
{
fileBytes = TEACrypter.DepadData(fileBytes);
}
break;
default:
throw new InvalidOperationException("Cryption settings are not valid: Desired cryption algorithm doesn't exist.");
}
return(fileBytes);
}
public void ShouldEncryptAndDecryptFullBlockByTEA()
{
var rnd = new Random(19);
var block = new byte[8];
var key = new byte[16];
rnd.NextBytes(block);
rnd.NextBytes(key);
var crypter = new TEACrypter(key);
var encrypt = crypter.Encrypt(block);
var decrypt = crypter.Decrypt(encrypt);
decrypt.Should().BeEquivalentTo(block, o => o.WithStrictOrdering());
}
public byte[] DecryptFile(byte[] encryptedBytes, string fileName)
{
var foundRecord = ReadRecord(fileName);
if (foundRecord == null)
{
throw new ArgumentException("There is no record for this file.");
}
CryptoChoice settings = foundRecord.Item1;
string originalFileHash = foundRecord.Item2;
byte[] fileBytes;
switch (settings.Choice)
{
case CryptoChoices.OneTimePad:
OneTimePadCrypter otp = new OneTimePadCrypter(settings.Key);
fileBytes = otp.Decrypt(encryptedBytes);
break;
case CryptoChoices.TEA:
TEACrypter tea = new TEACrypter(settings.Key);
fileBytes = tea.Decrypt(encryptedBytes);
if (settings.Depad)
{
fileBytes = TEACrypter.DepadData(fileBytes);
}
break;
default:
throw new InvalidOperationException("Cryption settings are not valid: Desired cryption algorithm doesn't exist.");
}
SHA1Hasher sha1 = new SHA1Hasher();
sha1.ComputeHash(fileBytes);
if (originalFileHash != sha1.HashedString)
{
throw new Exception("The hash value of the decrypted file and the original file hash value do not match. Access denied.");
}
return(fileBytes);
}
