Habbo V1 RC4 Encryption - C#

[Quackster]

Hello,

So I know this is 21 years late but I decided to try and get RC4 working in the very first version of Habbo, since we have the decompiled Habbo shockwave files, this was a task that only took me two days to complete!

Of course the RC4 in V1 can always be bypassed, but it's a cool feature to have regardless!

Screenshots:

How to use:

After you receive VERSIONCHECK, generate a public key (can be anything with letters and numbers) and then send these two packets below:

player.Send(new EncryptionOnComposer());
player.Send(new SecretKeyComposer(player.Connection.PublicKey));

Translates to

##ENCRYPTION_ON{13}#
##SECRET_KEY{13}PUBLIC_KEY{13}#

Initialise the RC4 with the decoded public key:

public void InitialiseEncryption()
{
    if (Encryption != null)
    {
        return;
    }

    Encryption = new RC4();
    Encryption.SetKey(SecretKey.SecretDecode(PublicKey));

    Channel.Pipeline.AddFirst("encryption", new EncryptionDecoder(this.Encryption));
}

And then any incoming packets after this will be enciphered by the client and must be deciphered by the server:

byte[] payload = new byte[buffer.ReadableBytes];
buffer.ReadBytes(payload);

var messagePayload = StringUtil.GetEncoding().GetString(payload);
var decodedPayload = StringUtil.GetEncoding().GetBytes(this.rc4.Decipher(messagePayload));

var result = Unpooled.Buffer();
result.WriteBytes(decodedPayload);
output.Add(result);

The RC4 and SecretKey classes I've written:

Ported from:

https://github.com/Quackster/habbo_src/blob/master/v1/src/script_FuseScript/RC4.ls

https://github.com/Quackster/habbo_src/blob/master/v1/src/script_FuseScript/Secret Key.ls

RC4:

/**
 * Habbo Hotel V1 RC4 class by Quackster (Alex)
 * Written in December 2021
 */

using System;
using System.Globalization;

namespace Euclid.Util.Encryption
{
    public class RC4
    {
        private int i;
        private int k;
        private int j;

        private int[] sbox;
        private int[] skey;

        /// <summary>
        /// Create key, not used, but ported from Habbo V1 RC4 class written in Lingo
        /// </summary>
        public int CreateKey()
        {
            var k = "";
            var random = new Random();
            var i = 0;

            while (i < 4)
            {
                k += int2hex(random.Next(256) - 1);
                i++;
            }

            return Math.Abs(hex2int(k));
        }

        /// <summary>
        /// Initialise the encryption class
        /// </summary>
        /// <param name="myKey"></param>
        public void SetKey(int myKey)
        {
            // Console.WriteLine("New key assigned to RC4: " + myKey);
           
            skey = new int[256];
            sbox = new int[256];

            i = 0;
            k = 0;

            var tempKey = Convert.ToString(myKey);

            while (i <= 255)
            {
                skey[i] = (int)tempKey[i % tempKey.Length];
                sbox[i] = i;
                i = 1 + i;
            }

            i = 0;
            j = 0;

            while (i <= 255)
            {
                j = (j + sbox[i] + skey[i]) % 256;
                k = sbox[i];
                sbox[i] = sbox[j];
                sbox[j] = k;
                i = 1 + i;
            }


            i = 0;
            j = 0;

            //Print(sbox);
            //Print(skey);
        }

        /// <summary>
        /// Recreate the enciphering performed on the client
        /// </summary>
        public string Encipher(string data)
        {
            string cipher = string.Empty;
            int a = 0;

            while (a < data.Length)
            {
                cipher += int2hex(data[a] ^ shift());
                a++;
            }

            return cipher;
        }

        /// <summary>
        /// Decipher incoming packets from client
        /// </summary>
        public string Decipher(string data)
        {
            string cipher = string.Empty;
            int a = 0;

            while (a < data.Length)
            {
                var t = hex2int(data.Substring(a, 2));
                cipher += (char)(t ^ shift());
                a += 2;
            }

            return cipher;
        }

        /// <summary>
        /// Shift RC4 tables
        /// </summary>
        private int shift()
        {
            i = (i + 1) % 256;
            j = (j + sbox[i]) % 256;
            var temp = sbox[i];
            sbox[i] = sbox[j];
            sbox[j] = temp;
            return sbox[(sbox[i] + sbox[j]) % 256];
        }

        /// <summary>
        /// int2hex ported from Lingo
        /// </summary>
        public static string int2hex(int aint)
        {
            var digits = "0123456789ABCDEF";
            var hexstr = "";

            if (aint <= 0)
                hexstr = "00";
            else
            {
                while (aint > 0)
                {
                    var sd = (aint % 16);
                    aint /= 16;
                    hexstr = digits[sd] + hexstr;
                }
            }

            if ((hexstr.Length % 2) == 1)
                hexstr = "0" + hexstr;

            return hexstr;
        }

        /// <summary>
        /// hex2int method used for deciphering
        /// </summary>
        public static int hex2int(string ahex)
        {
            return int.Parse(ahex, NumberStyles.HexNumber);
        }
       
        /// <summary>
        /// Used for debugging tables
        /// </summary>
        private void Print(int[] array)
        {
            foreach (int i in array)
                Console.Write(i + ", ");

            Console.WriteLine();
        }
    }
}

SecretKey:

/**
 * Habbo Hotel V1 RC4 class by Quackster (Alex)
 * Written in December 2021
 */

namespace Euclid.Util.Encryption
{
    public class SecretKey
    {
        /// <summary>
        /// Decode the secret sent from client
        /// </summary>
        public static int SecretDecode(string key)
        {
            string table = key.Substring(0, key.Length / 2); ;
            string tempKey = key.Substring(key.Length / 2);

            int checkSum = 0;
            int i = 0;

            while (i < tempKey.Length)
            {
                var a = table.IndexOf(tempKey[i]);

                if (a % 2 == 0)
                {
                    a *= 2;
                }

                if (i % 3 == 0)
                {
                    a *= 3;
                }

                if (a < 0)
                {
                    a = (tempKey.Length % 2);
                }

                checkSum += a;
                i++;
            }

            return checkSum;
        }
    }
}