function decryptCharcode(n,start,end,offset) {
			n = n + offset;
        	if (offset > 0 && n > end)	{
				n = start + (n - end - 1);
			} else if (offset < 0 && n < start)	{
				n = end - (start - n - 1);
			}
			return String.fromCharCode(n);
		}
		  // decrypt string
		function decryptString(enc,offset) {
			var dec = "";
			var len = enc.length;
			for(var i=0; i < len; i++)	{
				var n = enc.charCodeAt(i);
				if (n >= 0x2B && n <= 0x39)	{
					dec += decryptCharcode(n,0x2B,0x3A,offset);	// 0-9 . , - + / :
				} else if (n >= 0x40 && n <= 0x5A)	{
					dec += decryptCharcode(n,0x40,0x5A,offset);	// A-Z @
				} else if (n >= 0x61 && n <= 0x7A)	{
					dec += decryptCharcode(n,0x61,0x7A,offset);	// a-z
				} else {
					dec += enc.charAt(i);
			}
		}
			return dec;
		}