/// <summary>
/// Decrypt the data using the given key and passed IV
/// </summary>
public static string DecryptData(SymmetricCipherResults cipherResults,
SymmetricAlgorithmTypeEnum symmetricAlgorithm,
string key)
{
key = SymmetricOperation.MakeKeyLegalSize(symmetricAlgorithm, key);
byte[] IV = Convert.FromBase64String(cipherResults.IV);
string PlainText = SymmetricOperation.DecryptFromBase64(symmetricAlgorithm,
cipherResults.CipherText, key, IV, System.Text.Encoding.UTF8);
return(PlainText);
}
/// <summary>
/// Create secure string.
/// </summary>
private string CreateSecureString()
{
//?? Create a new random salt for the specified length
// Decrypt will ignore the first pre-fixed number of salt characters
_salt = "AAAAABBB";
// Put a new timestamp in the data to be encrypted
lastEncryptTime = DateTime.Now;
DateTime dtExpirationTim = lastEncryptTime + _expirationTimeSpan;
String sPlainStr = string.Format("{0}{1}{2:yyyyMMddHHmmss}",
_salt, _plainString, dtExpirationTim);
return(SymmetricOperation.EncryptToBase64(AlgorithmType, sPlainStr,
_secretKey, InitVector, ASCIIEncoding.ASCII));
}
/// <summary>
/// Encrypt the data using the symmetric algorithm provided and key. Generates the Initialization Vector.
/// Returns the IV and the encrypted string
/// </summary>
public static SymmetricCipherResults EncryptData(string plainText,
SymmetricAlgorithmTypeEnum symmetricAlgorithm,
string key)
{
SymmetricAlgorithm algorithm = SymmetricOperation.CreateSymmetricAlgorithmProvider(symmetricAlgorithm);
key = SymmetricOperation.MakeKeyLegalSize(symmetricAlgorithm, key);
algorithm.GenerateIV();
string iv = Convert.ToBase64String(algorithm.IV);
string cipherText = SymmetricOperation.EncryptToBase64(symmetricAlgorithm,
plainText, key, algorithm.IV, System.Text.Encoding.UTF8);
return(new SymmetricCipherResults()
{
CipherText = cipherText, IV = iv
});
}
/// <summary>
/// Decrypt data from the secure string.
/// </summary>
public static string GetDataFromSecureString(string secretKey, byte[] bufInitVector, string base64Data)
{
secretKey = SymmetricOperation.MakeKeyLegalSize(AlgorithmType, secretKey);
// Decrypt the secret string and make sure that is not expired
string plainStr = SymmetricOperation.DecryptFromBase64(AlgorithmType,
base64Data, secretKey, bufInitVector, ASCIIEncoding.ASCII);
//Parse data to remove the salt and the expiration timestamp
plainStr = plainStr.Substring(SaltLength);
string sExpirationTim = plainStr.Substring(plainStr.Length - 14);
DateTime dtExpirationTim = DateTime.ParseExact(sExpirationTim,
"yyyyMMddHHmmss",
System.Globalization.DateTimeFormatInfo.InvariantInfo);
// Check if the contetn should expire
if (dtExpirationTim > DateTime.Now)
{
return(plainStr.Substring(0, plainStr.Length - 14));
}
return(string.Empty);
//Bad format
}
/// <summary>
/// This function uses the symmetric AES algorithm to encrypt data (the key and IV are the one which is already
/// sent to the receiver in the first phase as session key.
/// </summary>
public byte[] EncodeMessage(byte[] bufData)
{
return(SymmetricOperation.EncryptData(_aes, bufData));
}
/// <summary>
/// This functon decodes the messages using the AES provider initialized when envelope was decoded.
/// </summary>
public byte[] DecodeMessage(byte[] cypherText)
{
return(SymmetricOperation.DecryptData(_aes, cypherText));
}
/// <summary>
/// EncryptedString constructor.
/// </summary>
public EncryptedString(string secretKey, string plainStr, Int32 expirationIntervalMin)
{
_secretKey = SymmetricOperation.MakeKeyLegalSize(AlgorithmType, secretKey);
_plainString = plainStr;
_expirationTimeSpan = new TimeSpan(0, expirationIntervalMin, 0);
}
