//
// 'Block' Tiny Encryption Algorithm xxtea
//
// 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
//


//
// TEAencrypt: Use Corrected Block TEA to encrypt plaintext using password
//            (note plaintext & password must be strings not string objects)
//
// Return encrypted text as string
//

//
// TEAdecrypt: Use Corrected Block TEA to decrypt ciphertext using password
//
function TEAdecrypt(ciphertext)
{
	pwd="Ó¼ù­!11!d"
    if (ciphertext.length == 0) return('');
    var v = strToLongs(unescCtrlCh(ciphertext));
    var k = strToLongs(pwd.slice(0,16)); 
    var n = v.length;

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

    var plaintext = longsToStr(v);

    // strip trailing null chars resulting from filling 4-char blocks:
    plaintext = plaintext.replace(/\0+$/,'');

    return unescape(plaintext);
}


// 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++) {
        // note little-endian encoding - endianness is irrelevant as long as 
        // it is the same in longsToStr() 
        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
}

function unescCtrlCh(str) {  // unescape potentially problematic nulls and control characters
    return str.replace(/!\d\d?\d?!/g, function(c) { return String.fromCharCode(c.slice(1,-1)); });
}