///<summary>
/// Encrypts a file using Rijndael algorithm.
///</summary>
///<param name="inputFile"></param>
///<param name="outputFile"></param>
private void EncryptFile(string inputFile, string outputFile)
{

try
{
string password = @"myKey123"; // Your Key Here
UnicodeEncoding UE = new UnicodeEncoding();
byte[] key = UE.GetBytes(password);

string cryptFile = outputFile;
FileStream fsCrypt = new FileStream(cryptFile, FileMode.Create);

RijndaelManaged RMCrypto = new RijndaelManaged();

CryptoStream cs = new CryptoStream(fsCrypt,
RMCrypto.CreateEncryptor(key, key),
CryptoStreamMode.Write);

FileStream fsIn = new FileStream(inputFile, FileMode.Open);

int data;
while ((data = fsIn.ReadByte()) != -1)
cs.WriteByte((byte)data);


fsIn.Close();
cs.Close();
fsCrypt.Close();
}
catch
{
MessageBox.Show("Encryption failed!", "Error");
}
}

///<summary>
/// Decrypts a file using Rijndael algorithm.
///</summary>
///<param name="inputFile"></param>
///<param name="outputFile"></param>
private void DecryptFile(string inputFile, string outputFile)
{

{
string password = @"myKey123"; // Your Key Here

UnicodeEncoding UE = new UnicodeEncoding();
byte[] key = UE.GetBytes(password);

FileStream fsCrypt = new FileStream(inputFile, FileMode.Open);

RijndaelManaged RMCrypto = new RijndaelManaged();

CryptoStream cs = new CryptoStream(fsCrypt,
RMCrypto.CreateDecryptor(key, key),
CryptoStreamMode.Read);

FileStream fsOut = new FileStream(outputFile, FileMode.Create);

int data;
while ((data = cs.ReadByte()) != -1)
fsOut.WriteByte((byte)data);

fsOut.Close();
cs.Close();
fsCrypt.Close();

}
}