CipherLinx® counters brute force attacks by making the key so large that it is not practical to try each one. CipherLinx's 80-bit address would take about 4789 trillion years to try each address at eight addresses per second. CipherLinx counters code grabbing by using a 40-bit counter that changes with each packet, not just every button press. At the fastest baud rate, the counter would take 890 years to run out. At this point, the system needs a new key. Encrypting the same data with a different key gives a different result. This ensures that the same transmission will never be sent twice, so an old transmission will never be accepted. The encryption portion of CipherLinx is based on the powerful Skipjack algorithm developed by the US National Security Agency (NSA). There are no known successful attacks on the Skipjack algorithm. CipherLinx improves on Skipjack by mixing the data with multiple calls to the encryption algorithm. CipherLinx responds to the threat of physical attack by allowing the optional creation of a PIN that must be entered before the transmitter will activate.