Secure External RPC communication (how do i make it secure?)

// horrid hack because LSL doesn't seem to have llStringToASCII or equivalent...
list ascii = [
" ", "!", "\"", ...  "?",
"@", "A", "B", ... "Z", "[", ... "_",
"`", "a", "b", "c", "d", "e", ... "z", ... "~"
];
integer ASCII_LEN = 95; // 128 ASCII characters, less 32 control, less DEL
list key = [ 11, 34, 89, 61, ... 47 ];
integer key_channel = 67846738; // Keep this uber-secret

string decode(string ciphertext)
{
  integer len = llGetStringLength(ciphertext);
  string plaintext = "";
  integer keylen = llGetListLength(key);
  integer i;
  integer j = 0;
  integer charval;
  string chartext;

  for(i = 0; i < len; i++)
  {
    charval = llListFindList(ascii, [ llGetSubString(ciphertext, i, i) ]);
    if(charval != -1)
    {
      charval = (charval + llList2Integer(key, j)) % ASCII_LEN;
      chartext = llList2String(ascii, charval);
      plaintext = plaintext + chartext;
      j = j + 1;
      if(j >= keylen) j = 0;
    }
    else if(chartext != " ")
    {
      plaintext = plaintext + " ";
      chartext = " ";
    }
  }
  return plaintext;
}

// horrid hack because LSL doesn't seem to have llStringToASCII or equivalent...

iinteger UTF8ToUnicodeInteger(string a)
{
    //{//Convert our data into a nice byte list;
        string b = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
        integer d = llSubStringIndex((a = llStringToBase64(a))+"=","=");
        integer e = 0;
        list f;
        if(d>8)
            d = 8;
        integer i = 0;
        while(e < d)
        {
            i = (i << 6) | (llSubStringIndex(b,llGetSubString(a,e,e)) % 64);
            if(!(++e % 4))
                f += [(i >> 16) & 0xff,(i >> 8) & 0xff,i & 0xff];
        }
        if(e = (6 * (e % 4)))
            f += [((i << 8) >> e) & 0xff,((i << 16) >> e) & 0xff,(i << (24 - e)) & 0xff];
    //}
    i = llList2Integer(f,0);
    if( i < 0xC0) //11000000
    {
        if((4 <= 3 * d) && !(i & 0x80))
            return i;
    }
    else if( i < 0xFE ) //11111110
    {
        e = llList2Integer(f,1);
        if( i < 0xE0) //11100000
        {
            if((8 <= 3 * d) && (i & 0x1E) && ((e & 0xC0) == 0x80))
                return ((i & 0x1F) << 6) | (e & 0x3F);
        }
        else
        {
            integer c = 6;
            if( i < 0xF0) //11110000
                c = 3;
            else if( i < 0xF8) //11111000
                c = 4;
            else if( i < 0xFC) //11111100
                c = 5;
            if(4*c <= 3 * d && (e & (0x1F80 >> c)) != 0x80)
            {
                d = i & (0x7f >> c);
                integer g = 1;
                e = (d << 6) | (e & 0x3f);
                while(++g < c)
                {
                    e = (e << 6) | ((d = llList2Integer(f,g)) & 0x3f);
                    if((d & 0xC0) != 0x80)
                        jump error;
                }
                return e;
            }
        }
    }
    @error;
    return i | 0x80000000;
}


string byte2hex(integer x) 
{
    string hexc="0123456789ABCDEF";
    integer x0  = (x & 0xF);
    return llGetSubString(hexc, x0 = ((x >> 4) & 0xF), x0) + llGetSubString(hexc, x0, x0);
}

string UnicodeIntegerToUTF8(integer a)
{
    if(a <= 0) return "";
    integer b = 0;
    integer c = 0;
    string d;
    if (a >= 0x4000000)
        c = 5;
    else if (a >= 0x200000)
        c = 4;
    else if (a >= 0x10000)
        c = 3;
    else if (a >= 0x800)
        c = 2;
    else if (a >= 0x80)
        c = 1;
    while(b < c)
        d = "%" + byte2hex((((a >> (6 * b++)) | 0x80) & 0xBF)) + d;
    d = "%" + byte2hex((a >> (6 * c)) | ((0x3F80 >> c) * (0 != c))) + d;
    return llUnescapeURL(d);
}