Q:

Merge the DES Helper into UWP? 

i'm using this method to encrypt/decrypt my data, but the windows universal app just do not support System. Security. Cryptography.  So how can I just transplant these into UWP apps?  thanks 
    static string DES_Key = "lolhahaha";
    public static string DESEncrypt(string data)
    {
        try
        {
            string timeStamp = DateTime. Now. ToString("sss");

            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            byte[] inputByteArray = Encoding. UTF8.GetBytes(data + timeStamp);

            des. Key = ASCIIEncoding. ASCII.GetBytes(DES_Key);
            des. IV = ASCIIEncoding. ASCII.GetBytes(DES_Key);

            MemoryStream ms = new MemoryStream();
            CryptoStream cs = new CryptoStream(ms, des. CreateEncryptor(), CryptoStreamMode. Write);

            cs. Write(inputByteArray, 0, inputByteArray. Length);
            cs. FlushFinalBlock();
            byte[] buffer = ms. ToArray();
            ms. Close();

            return Convert. ToBase64String(buffer);
        }
        catch (Exception ex)
        {
            return "";
        }
    }

A:

but the windows universal app just do not support System. Security. Cryptography. 

Why you said so?  Windows. Security. Cryptography namespace is supported in UWP apps, you can use CryptographicBuffer class instead to encrypt and decrypt data.  
Here in SymmetricKeyAlgorithmProvider class is code sample you may take a look.  And you can find the supported algorithms in SymmetricAlgorithmNames class.