public static DecryptionResult DecryptText(string inputText, string password)
{
DecryptionResult decryptionResult = null;
try
{
byte[] EncryptedBytes = null;
try
{
EncryptedBytes = System.Text.Encoding.UTF8.GetBytes(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;
}
return decryptionResult;
}
public async static Task<DecryptionResult> DecryptFile(Windows.Storage.StorageFile inputFile, string password)
{
DecryptionResult decryptionResult = null;
try
{
byte[] FileContentBytes = null;
using (Stream stream = await inputFile.OpenStreamForReadAsync())
{
using (var memoryStream = new MemoryStream())
{
stream.CopyTo(memoryStream);
FileContentBytes = memoryStream.ToArray();
}
}
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);
int Blocks128000Size = EncryptedBytes.Length / 128000;
int LastBlockSize = EncryptedBytes.Length % 128000;
ctr = 0;
byte[] DecryptedBytes = new byte[EncryptedBytes.Length];
for (long i = 0; i < Blocks128000Size; i++)
{
byte[] input = new byte[128000];
System.Buffer.BlockCopy(EncryptedBytes, ctr, input, 0, 128000);
byte[] result = DecryptionService.GetDecryptedByteArray(input, passwordBytes);
System.Buffer.BlockCopy(result, 0, DecryptedBytes, ctr, 128000);
ctr = ctr + 128000;
}
if (LastBlockSize > 0)
{
byte[] input = new byte[LastBlockSize];
System.Buffer.BlockCopy(EncryptedBytes, ctr, input, 0, LastBlockSize);
byte[] result = DecryptionService.GetDecryptedByteArray(input, passwordBytes);
System.Buffer.BlockCopy(result, 0, DecryptedBytes, ctr, LastBlockSize);
}
string CurrentDirectoryPath = System.IO.Path.GetDirectoryName(inputFile.Path);
string CurrentFileName = System.Text.Encoding.ASCII.GetString(FileNameBytes) + "_1";
string CurrentFileExtension = System.Text.Encoding.ASCII.GetString(ExtensionBytes);
string WritePath = System.IO.Path.Combine(CurrentDirectoryPath, CurrentFileName + CurrentFileExtension);
decryptionResult = new DecryptionResult()
{
Result = true,
Error = null,
DecryptedString = null,
DecryptedContents = DecryptedBytes,
WritePath = WritePath
};
}
catch (Exception ex)
{
decryptionResult = new DecryptionResult()
{
Result = false,
Error = ex.Message,
DecryptedString = null
};
}
return decryptionResult;
}
