Compsci 82, Fall 2008, Sept 17

By entering your name/net-id below you indicate you are in class on Sept 17 to answer these questions. 
Name: ______________________________    Net id: _____________


Name: ______________________________    Net id: _____________


Name: ______________________________    Net id: _____________


Name: ______________________________    Net id: _____________
  1. If IANA/ICANN gives out one billion IP addresses a second using IPv4, how long will it take to give out every possible address? Justify your answer.
  2. Suppose IPv6 is used instead of IPv4, but still one billion IP addresses are given out each second. How long will it take to give out every possible address? Justify your answer.
  3. The EFF's Deep Crack, built for $250,000 and shown below can break a 40-bit/DES key in about one day (between 23 and 24 hours) using a brute-force attack.

    deepcrackimage

    1. How long will it take to break a 41-bit key using this machine/approach? Why?
    2. How long will it take to break a 50-bit key using this machine/approachy? Why?
    3. If we interpret Moore's law as doubling the speed of computing every two years, in the year 2010 it will take half-a-day to break a 40-bit DES key instead of 24 hours. In 2012 it will take 6 hours. In what year will it take less than a minute to break a 40-bit DES key?
    4. Skype uses a 256-bit key for its encryption. If we assume Moore's law continues for 100 years, computers in 2108 will be quite powerful. Suppose Moore's law continues to hold using quantum-computing or some other technology. Scientists and theologians pretty much agree that the universe is less than 20 billion years old. Will brute-force attacks by computers in another 20 billion years break Skype's 256-bit encryption key? Why?