public string DecryptString(string input, string passwordToBeUsedInSecreKey)
{
input = input.Replace('|', '=');
input = input.Replace('_', '/');
input = input.Replace('¬', '+');
SymmetricParameters myParameters = GenerateSymmetricParameters(passwordToBeUsedInSecreKey);
Rijndael myAlg = Rijndael.Create();
myAlg.Key = myParameters.SecretKey;
myAlg.IV = myParameters.IV;
byte[] encryptedDataAsBytes = Convert.FromBase64String(input); //Converting user input to byte[]
MemoryStream msEncryptedData = new MemoryStream(encryptedDataAsBytes);
CryptoStream cs = new CryptoStream(msEncryptedData, myAlg.CreateDecryptor(), CryptoStreamMode.Read);
MemoryStream msClearData = new MemoryStream();
cs.CopyTo(msClearData);
byte[] clearDataAsBytes = msClearData.ToArray();
string clearData = Encoding.UTF32.GetString(clearDataAsBytes); //converting the cryptographic data to string
return(clearData);
}
public Stream HybridEncryptFile(Stream article, string username, string publickey)
{
//1. Generate the secret key and the IV from the username
//>> SymmetricParameters
SymmetricParameters myParameters = GenerateSymmetricParameters(username);
//2.Encrypt the file using the methodEncryptSymmetricallyFile with the parameters from step 1.
Stream encrypted = EncryptSymmetricallyFile(article, myParameters);
//3. encrypt the secret key and the iv using the public key and using the method EncryptAsymmetricallyKey
Stream encryptedSecretKey = EncryptAsymmetricallyKey(myParameters.SecretKey, publickey);
Stream encryptedIV = EncryptAsymmetricallyKey(myParameters.IV, publickey);
//4. you store the encrypted secret key(from no.3) + the encrypted iv (from no.3) + encrypted file content (from no.2)
MemoryStream msEncryptedFile = new MemoryStream();
encryptedSecretKey.Position = 0;
encryptedIV.Position = 0;
encryptedSecretKey.CopyTo(msEncryptedFile);
encryptedIV.CopyTo(msEncryptedFile);
encrypted.Position = 0;
encrypted.CopyTo(msEncryptedFile);
return(msEncryptedFile);
}
public SymmetricParameters GenerateSymmetricParameters(string input)
{
Rfc2898DeriveBytes rfc = new Rfc2898DeriveBytes(input, new byte[] { 20, 255, 1, 16, 54, 78, 68, 10, 52, 38, 20, 87, 91 });
Rijndael myAlg = Rijndael.Create();
SymmetricParameters myParams = new SymmetricParameters()
{
SecretKey = rfc.GetBytes(myAlg.KeySize / 8),
IV = rfc.GetBytes(myAlg.BlockSize / 8)
};
return(myParams);
}
public MemoryStream EncryptSymmetricallyFile(Stream input, SymmetricParameters myParameters)
{
Rijndael myAlg = Rijndael.Create();
myAlg.Key = myParameters.SecretKey;
myAlg.IV = myParameters.IV;
CryptoStream cs = new CryptoStream(input, myAlg.CreateEncryptor(), CryptoStreamMode.Read);
MemoryStream msEncryptedData = new MemoryStream();
cs.CopyTo(msEncryptedData);
return(msEncryptedData);
}
