Nostale World Encryption

public static string Decrypt2(string str)
        {
            List<byte> receiveData = new List<byte>();
            char[] table = { ' ', '-', '.', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'n' };
            int count;
            for (count = 0; count < str.Length; count++)
            {
                if (str[count] <= 0x7A)
                {
                    int len = str[count];

                    for (int i = 0; i < len; i++)
                    {
                        count++;

                        try
                        {
                            receiveData.Add(unchecked((byte)(str[count] ^ 0xFF)));
                        }
                        catch
                        {
                            receiveData.Add(255);
                        }
                    }
                }
                else
                {
                    int len = str[count];
                    len &= 0x7F;

                    for (int i = 0; i < len; i++)
                    {
                        count++;
                        int highbyte;
                        try
                        {
                            highbyte = str[count];
                        }
                        catch
                        {
                            highbyte = 0;
                        }
                        highbyte &= 0xF0;
                        highbyte >>= 0x4;

                        int lowbyte;
                        try
                        {
                            lowbyte = str[count];
                        }
                        catch
                        {
                            lowbyte = 0;
                        }
                        lowbyte &= 0x0F;

                        if (highbyte != 0x0 && highbyte != 0xF)
                        {
                            receiveData.Add(unchecked((byte)table[highbyte - 1]));
                            i++;
                        }

                        if (lowbyte != 0x0 && lowbyte != 0xF)
                        {
                            receiveData.Add(unchecked((byte)table[lowbyte - 1]));
                        }
                    }
                }
            }
            return Encoding.UTF8.GetString(Encoding.Convert(Encoding.Default, Encoding.UTF8, receiveData.ToArray()));
}

public override string Decrypt(byte[] str, int sessionId = 0)
        {
            string encrypted_string = "";
            int session_key = sessionId & 0xFF;
            byte session_number = unchecked((byte)(sessionId >> 6));
            session_number &= 0xFF;
            session_number &= unchecked((byte)0x80000003);

            switch (session_number)
            {
                case 0:
                    foreach (byte character in str)
                    {
                        byte firstbyte = unchecked((byte)(session_key + 0x40));
                        byte highbyte = unchecked((byte)(character - firstbyte));
                        encrypted_string += (char)highbyte;
                    }
                    break;

                case 1:
                    foreach (byte character in str)
                    {
                        byte firstbyte = unchecked((byte)(session_key + 0x40));
                        byte highbyte = unchecked((byte)(character + firstbyte));
                        encrypted_string += (char)highbyte;
                    }
                    break;

                case 2:
                    foreach (byte character in str)
                    {
                        byte firstbyte = unchecked((byte)(session_key + 0x40));
                        byte highbyte = unchecked((byte)(character - firstbyte ^ 0xC3));
                        encrypted_string += (char)highbyte;
                    }
                    break;

                case 3:
                    foreach (byte character in str)
                    {
                        byte firstbyte = unchecked((byte)(session_key + 0x40));
                        byte highbyte = unchecked((byte)(character + firstbyte ^ 0xC3));
                        encrypted_string += (char)highbyte;
                    }
                    break;

                default:
                    encrypted_string += (char)0xF;
                    break;
            }

            string[] temp = encrypted_string.Split((char)0xFF);
            string save = "";

            for (int i = 0; i < temp.Length; i++)
            {
                save += Decrypt2(temp[i]);
                if (i < temp.Length - 2)
                {
                    save += (char)0xFF;
                }
            }

            return save;
}

def decrypt2(_packet):
    decrypted_string = ''
    table = [' ', '-', '.', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'n']

    count = 0
    while count < len(_packet):
        if ord(_packet[count]) <= 0x7A:
            _len = ord(_packet[count])
            for i in range(1, _len):
                count += 1
                decrypted_string += chr(ord(_packet[count]) ^ 0xFF)
        else:
            _len = ord(_packet[count])
            _len &= 0x7F

            i = 0
            while i < _len:
                count += 1

                try:
                    highbyte = ord(_packet[count])
                    highbyte &= 0xF0
                    highbyte >>= 0x4
                except IndexError:
                    highbyte = 0

                try:
                    lowbyte = ord(_packet[count])
                    lowbyte &= 0x0F
                except IndexError:
                    lowbyte = 0

                if highbyte != 0x0 and highbyte != 0xF:
                    decrypted_string += table[highbyte - 1]

                if lowbyte != 0x0 and lowbyte != 0xF:
                    decrypted_string += table[lowbyte - 1]

                i += 1
            count += 1
    print('Decrypted:', decrypted_string)
    return decrypted_string

def decrypt(_packet, session_id):
    encrypted_string = ""
    session_key = session_id & 0xFF
    session_number = session_id >> 6
    session_number &= 0xFF
    session_number &= 0x80000003


    if session_number == 0:
        for i in range(0, len(_packet)):
            firstbyte = session_key + 0x40
            highbyte = (int(_packet[i]) - firstbyte)
            encrypted_string += chr(highbyte)
    elif session_number == 1:
        for i in range(0, len(_packet)):
            firstbyte = session_key + 0x40
            highbyte = (int(_packet[i]) + firstbyte)
            encrypted_string += chr(highbyte)
    elif session_number == 2:
        for i in range(0, len(_packet)):
            firstbyte = session_key + 0x40
            highbyte = (int(_packet[i]) - firstbyte) ^ 0xC3
            encrypted_string += chr(highbyte)
    elif session_number == 3:
        for i in range(0, len(_packet)):
            firstbyte = session_key + 0x40
            highbyte = (int(_packet[i]) + firstbyte) ^ 0xC3
            encrypted_string += chr(highbyte)
    else:
        encrypted_string += chr(0xF)

    temp = encrypted_string.split(chr(0xFF))
    save = ""

    for i in range(0, len(temp)):
        save += decrypt2(temp[i])
        if i < len(temp[i]) -2:
            save += chr(0xFF)

    return save