public static DecryptionResult DecryptText(string inputText, string password)
{
ReaderWriterLockSlim locker = new ReaderWriterLockSlim();
DecryptionResult decryptionResult = null;
try
{
locker.EnterReadLock();
byte[] EncryptedBytes = null;
try
{
EncryptedBytes = System.Convert.FromBase64String(inputText);
}
catch (Exception)
{
decryptionResult = new DecryptionResult()
{
Result = false,
Error = "Text is not a valid encrypted message",
DecryptedString = null
};
return(decryptionResult);
}
byte[] passwordBytes = System.Text.Encoding.UTF8.GetBytes(password);
passwordBytes = SHA256.Create().ComputeHash(passwordBytes);
byte[] DecryptedBytes = DecryptionService.GetDecryptedByteArray(EncryptedBytes, passwordBytes);
try
{
decryptionResult = new DecryptionResult()
{
DecryptedString = System.Text.Encoding.UTF8.GetString(DecryptedBytes),
Result = true,
Error = null
};
}
catch (Exception)
{
decryptionResult = new DecryptionResult()
{
Result = false,
Error = "Text is not a valid encrypted message",
DecryptedString = null
};
return(decryptionResult);
}
}
catch (Exception ex)
{
decryptionResult.Result = false;
decryptionResult.Error = ex.Message;
}
finally
{
locker.ExitReadLock();
}
return(decryptionResult);
}
public static DecryptionResult DecryptFile(string inputFile, string password)
{
DecryptionResult decryptionResult = null;
ReaderWriterLockSlim locker = new ReaderWriterLockSlim();
try
{
locker.EnterReadLock();
byte[] FileContentBytes = File.ReadAllBytes(inputFile);
int ctr = 0;
for (int i = 999; i >= 0; i--)
{
if (FileContentBytes[i] != 0)
{
ctr = i;
break;
}
}
int ctr2 = 1000;
for (int i = 1999; i >= 1000; i--)
{
if (FileContentBytes[i] != 0)
{
ctr2 = i;
break;
}
}
int FileNameBytesLength = ctr + 1;
int ExtensionBytesLength = ctr2 + 1 - 1000;
byte[] passwordBytes = SHA256.Create().ComputeHash(System.Text.Encoding.ASCII.GetBytes(password));
byte[] SaltedHashedPassword = SHA256.Create().ComputeHash(System.Text.Encoding.ASCII.GetBytes(password + "CryptoApp"));
byte[] FileNameBytes = new byte[FileNameBytesLength];
byte[] ExtensionBytes = new byte[ExtensionBytesLength];
byte[] StoredHashedPassword = new byte[32];
byte[] EncryptedBytes = new byte[FileContentBytes.Length - 2032];
System.Buffer.BlockCopy(FileContentBytes, 2000, StoredHashedPassword, 0, 32);
bool ArePasswordsSame = true;
for (int i = 0; i < 32; i++)
{
if (SaltedHashedPassword[i] != StoredHashedPassword[i])
{
ArePasswordsSame = false;
break;
}
}
if (ArePasswordsSame == false)
{
decryptionResult = new DecryptionResult()
{
Result = false,
Error = "Password",
DecryptedString = null
};
return(decryptionResult);
}
System.Buffer.BlockCopy(FileContentBytes, 0, FileNameBytes, 0, FileNameBytesLength);
System.Buffer.BlockCopy(FileContentBytes, 1000, ExtensionBytes, 0, ExtensionBytesLength);
System.Buffer.BlockCopy(FileContentBytes, 2032, EncryptedBytes, 0, EncryptedBytes.Length);
byte[] DecryptedBytes = DecryptionService.GetDecryptedByteArray(EncryptedBytes, passwordBytes);
string CurrentDirectoryPath = Path.Combine(Android.OS.Environment.ExternalStorageDirectory.Path, "Crypto App");
if (!Directory.Exists(CurrentDirectoryPath))
{
System.IO.Directory.CreateDirectory(CurrentDirectoryPath);
}
string CurrentFileName = System.Text.Encoding.ASCII.GetString(FileNameBytes);
string CurrentFileExtension = System.Text.Encoding.ASCII.GetString(ExtensionBytes);
string WritePath = System.IO.Path.Combine(CurrentDirectoryPath, CurrentFileName + CurrentFileExtension);
if (System.IO.File.Exists(WritePath))
{
Int64 ctr3 = 1;
var TempWritePath = System.IO.Path.Combine(CurrentDirectoryPath, CurrentFileName + "_" + ctr3.ToString() + CurrentFileExtension);
while (System.IO.File.Exists(TempWritePath) && ctr3 < int.MaxValue)
{
ctr3 = ctr3 + 1;
TempWritePath = System.IO.Path.Combine(CurrentDirectoryPath, CurrentFileName + "_" + ctr3.ToString() + CurrentFileExtension);
}
WritePath = TempWritePath;
}
File.WriteAllBytes(WritePath, DecryptedBytes);
decryptionResult = new DecryptionResult()
{
Result = true,
Error = null,
DecryptedString = System.IO.Path.GetFileName(WritePath)
};
}
catch (Exception ex)
{
decryptionResult = new DecryptionResult()
{
Result = false,
Error = ex.Message,
DecryptedString = null
};
}
finally
{
locker.ExitReadLock();
}
return(decryptionResult);
}
