title: UICC: Can I trust proactive TIMER MANAGEMENT?
body: <p>UICC (SIM card) has no internal clock. If an applet loaded on the SIM card needs to know, whether some time interval has already elapsed, it has to allocate a timer in the device and start it using TIMER MANAGEMENT proactive command.</p>
  
  <p>ETSI standard (102 223 V12.1.0) says: </p>
  
  <blockquote>
    <p>"The precision of the returned value cannot be relied upon in all
    cases due to potential terminal activities"</p>
  </blockquote>
  
  <p>Does it mean that the timer can fire the desired event even BEFORE it should?</p>
  
  <p>Is there any protection provided by OS against the timer event fraud (an attacker pretending the timer event has been fired)?</p>
  
  <p>Can I trust the timer even in some "serious" security applications, or is it just kind of a toy with a limited real world usage?</p>