Convert C# encryption mechanism code to javascript

Question

I have code to encrypt and decrypt the files in C#. Now I need to move the encryption task to front end an I need to write javascript code to encrypt the .xlsx files. Below is the C# code for encrypt and decrypt:

    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(Exception ex)
        {
           // MessageBox.Show("Encryption failed!", "Error");
        }
    }

    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();

        }
    }

I tried to create a encryption in javascript as below:

    var reader = new FileReader();
    reader.onload = function (e) {

        var encrypted = CryptoJS.AES.encrypt(e.target.result, 'myKey123');

        var data = new FormData();


        var encryptedFile = new File([encrypted], file.name, { type: "text/plain", lastModified: new Date() });

        data.append('file', encryptedFile);

        $.ajax({
            url: 'http://localhost:57691/api/WithKey/UploadFile',
            data: data,
            cache: false,
            contentType: false,
            processData: false,
            type: 'POST',
            success: function (data) {
                debugger;
            }
        });
    };

    reader.readAsDataURL(file);

I also tried converting key to utf16 as below:

    function wordsToBytes (words) {
        for (var bytes = [], b = 0; b < words.length * 32; b += 8)
            bytes.push((words[b >>> 5] >>> (24 - b % 32)) & 0xFF);
        return bytes;
    }
  var temp = CryptoJS.enc.Utf16.parse('myKey123');
  var key = wordsToBytes(temp.words);

But no luck. Can you please someone help me where I am doing wrong. What is the right way to encrypt the file in javascript as same in C#?

Why do you want to do this instead of using HTTPS? Your C# code leaks, you don't dispose all the things you need to dispose. — Alex K.
– Alex K., Commented Oct 17, 2016 at 13:00
I wonder why you've created a new account to ask a similar question like this one. Anyway, why do you need to port this C# code? It's terrible. Why don't you simply use RNCryptor which has implementations in several languages? — Artjom B.
– Artjom B., Commented Oct 17, 2016 at 18:47

Artjom B. · Accepted Answer · 2016-10-17 19:03:27Z

1

This is the JavaScript code that would produce the same ciphertext as the C# code. The problem that remains is that you need to transmit this somehow.

var keyWords = CryptoJS.enc.Utf16LE.parse("myKey123");
var encryptedWords = CryptoJS.AES.encrypt("some string", keyWords, { iv: keyWords }).ciphertext;
console.log("Hex: " + encryptedWords.toString());
console.log("Base64: " + encryptedWords.toString(CryptoJS.enc.Base64));

<script src="https://cdn.rawgit.com/CryptoStore/crypto-js/3.1.2/build/rollups/aes.js"></script>
<script src="https://cdn.rawgit.com/CryptoStore/crypto-js/3.1.2/build/components/enc-utf16-min.js"></script>

answered Oct 17, 2016 at 19:03

Artjom B.

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