var b = (str.charCodeAt(i) & 0xF0) >> 4;
retval += (b <= 9) ? String.fromCharCode(b + 48) : String.fromCharCode((b - 10) + 65);
b = str.charCodeAt(i) & 0x0F;
retval += (b <= 9) ? String.fromCharCode(b + 48) : String.fromCharCode((b - 10) + 65);