/// <summary>
/// Decript value preveously encripted by EncriptIntToHexString()
/// </summary>
/// <param name="value">Hex string, like "FFFFFFFF"</param>
/// <param name="skip32Key">The same key as was passed to EncriptIntToHexString()</param>
/// <param name="defaultValue">If a non-null value is passed, fail silently and return it. Otherwise throw.</param>
/// <returns>Original int value passed to EncriptIntToHexString()</returns>
public static int DecriptHexStringToInt(string value, string skip32Key, int?defaultValue = null)
{
try
{
if (skip32Key.Length != 10)
{
throw new ArgumentOutOfRangeException("The key must be 10 chars long.");
}
var unsigned = UInt32.Parse(value, NumberStyles.HexNumber);
var bytes = BitConverter.GetBytes(unsigned);
var encrypted = BitConverter.ToInt32(bytes, 0);
var cipher = new Eleven41.Skip32.Skip32Cipher(Encoding.ASCII.GetBytes(skip32Key));
return(cipher.Decrypt(encrypted));
}
catch
{
if (defaultValue.HasValue)
{
// Fail silently.
return(defaultValue.Value);
}
else
{
throw;
}
}
}
/// <summary>
/// Encript an int value into a 8-char hex string like "FFFFFFFF"
/// </summary>
/// <param name="value">Original value</param>
/// <param name="skip32Key">The key must be 10 chars long</param>
/// <returns>8-char hex string like "FFFFFFFF"</returns>
public static string EncriptIntToHexString(int value, string skip32Key)
{
if (skip32Key.Length != 10)
{
throw new ArgumentOutOfRangeException("The key must be 10 chars long.");
}
var cipher = new Eleven41.Skip32.Skip32Cipher(Encoding.ASCII.GetBytes(skip32Key));
var encrypted = cipher.Encrypt(value);
// Convert to UInt32 to avoid a sign.
var bytes = BitConverter.GetBytes(encrypted);
var unsigned = BitConverter.ToUInt32(bytes, 0);
var encryptedString = unsigned.ToString("X"); // 8 chars
return(encryptedString);
}
