Agent Affiliation

//--------------------------------------------------------------------------- // 'Block' Tiny Encryption Algorithm // // Algorithm: David Wheeler & Roger Needham, Cambridge University Computer Lab // http://www.cl.cam.ac.uk/ftp/papers/djw-rmn/djw-rmn-tea.html (1994) // http://www.cl.cam.ac.uk/ftp/users/djw3/xtea.ps (1997) // http://www.cl.cam.ac.uk/ftp/users/djw3/xxtea.ps (1998) // // JavaScript implementation: Chris Veness, Movable Type Ltd: www.movable-type.co.uk // // encrypt: Use 128 bits (16 chars) of string 'key' to encrypt string 'val' // (note key & val must be strings not string objects) // - return encrypted text as string // function encrypt(val, key) {

   // 'escape' val so chars outside ISO-8859-1 work in single-byte packing, but 
   // keep spaces as spaces (not '%20') so encrypted text doesn't grow too long!
   var v = strToLongs(escape(val).replace(/%20/g,' '));
   var k = strToLongs(key.slice(0,16)); var n = v.length;

   if (n == 0) return("");  // nothing to encrypt
   if (n == 1) v[n++] = 0;  // algorithm doesn't work for n<2 so fudge by adding nulls

   // TEA routine as per Wheeler & Needham, Oct 1998

   var z = v[n-1], y = v[0], delta = 0x9E3779B9;
   var mx, e, q = Math.floor(6 + 52/n), sum = 0;

   while (q-- > 0) {  // 6 + 52/n operations gives between 6 & 32 mixes on each word
       sum += delta;
       e = sum>>>2 & 3;
       for (var p = 0; p < n-1; p++) {
           y = v[p+1];
           mx = (z>>>5 ^ y<<2) + (y>>>3 ^ z<<4) ^ (sum^y) + (k[p&3 ^ e] ^ z)
           z = v[p] += mx;
       }
       y = v[0];
       mx = (z>>>5 ^ y<<2) + (y>>>3 ^ z<<4) ^ (sum^y) + (k[p&3 ^ e] ^ z)
       z = v[n-1] += mx;
   }

   // note: unsigned right-shift '>>>' is used in place of original '>>', 
   // due to lack of 'unsigned' type declaration in JavaScript

   return(escape(longsToStr(v)));

}

// // decrypt: use 128 bits of string 'key' to decrypt string 'val' encrypted as per above // function decrypt(val, key) {

   var v = strToLongs(unescape(val)); var k = strToLongs(key.slice(0,16)); var n = v.length;

   if (n == 0) return("");

   // TEA routine as per Wheeler & Needham, Oct 1998

   var z = v[n-1], y = v[0], delta = 0x9E3779B9;
   var mx, e, q = Math.floor(6 + 52/n), sum = q*delta;

   while (sum != 0) {
       e = sum>>>2 & 3;
       for (var p = n-1; p > 0; p--) {
           z = v[p-1];
           mx = (z>>>5 ^ y<<2) + (y>>>3 ^ z<<4) ^ (sum^y) + (k[p&3 ^ e] ^ z)
           y = v[p] -= mx;
       }
       z = v[n-1];
       mx = (z>>>5 ^ y<<2) + (y>>>3 ^ z<<4) ^ (sum^y) + (k[p&3 ^ e] ^ z)
       y = v[0] -= mx;
       sum -= delta;
   }

   var s = longsToStr(v);
   if (s.indexOf("\x00") != -1) {
       // strip trailing null chars resulting from filling 4-char blocks
       s = s.substr(0, s.indexOf("\x00"));
   }

   return unescape(s);

}

// supporting functions

function strToLongs(s) { // convert string to array of longs, each containing 4 chars

   // note chars must be within ISO-8859-1 (with Unicode code-point < 256) to fit 4/long
   var l = new Array(Math.ceil(s.length/4))
   for (var i=0; i<l.length; i++) {
       l[i] = s.charCodeAt(i*4) + (s.charCodeAt(i*4+1)<<8) + 
              (s.charCodeAt(i*4+2)<<16) + (s.charCodeAt(i*4+3)<<24);
   }
   return l;  // note running off the end of the string generates nulls since 

} // bitwise operators treat NaN as 0

function longsToStr(l) { // convert array of longs back to string

   var a = new Array(l.length);
   for (var i=0; i<l.length; i++) {
       a[i] = String.fromCharCode(l[i] & 0xFF, l[i]>>>8 & 0xFF, 
                                l[i]>>>16 & 0xFF, l[i]>>>24 & 0xFF);
   }

   return a.join();  // use Array.join() rather than repeated string appends for efficiency

} // end Encryption Algorithm //---------------------------------------------------------------------------

//The following goes into the sidebar portion of the template

Encryption Tool

<form name="et" action="none!">

<input type="text" name="key" size="12" value="key">

<textarea name="val" rows="1">value</textarea>

<script type="text/javascript">var ciferText;</script> <input type="button" value="Encrypt it" onClick='et.encrypted.value = ciferText = encrypt(et.val.value, et.key.value)' style="width: auto;background-color: #999;">

<textarea name="encrypted" rows="1"></textarea>

<input type="button" value="Decrypt it" onClick='et.decrypted.value = decrypt(et.val.value, et.key.value)' style="width: auto;background-color: #999;">

<textarea name="decrypted" rows="1"></textarea>

   </form>