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Discrete Logs, Diffie-Hellman, ElGamal: Quiz, Term Project, HW Due Tomorrow - Announcements

This announcement provides information on a short quiz on Chapter 3, the formation of term project groups and topics, and the due date for HW6. It also highlights the topics covered this week, including Discrete Logs, Diffie-Hellman, and ElGamal.

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Discrete Logs, Diffie-Hellman, ElGamal: Quiz, Term Project, HW Due Tomorrow - Announcements

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  1. DTTF/NB479: Dszquphsbqiz Day 25 • Announcements: • Short “pop” quiz on Ch 3 (today?) • Term project groups and topics formed • HW6 due tomorrow. • Questions? • This week: • Discrete Logs, Diffie-Hellman, ElGamal • Hash Functions

  2. Discrete Logs Given Find x We denote this as Why is this hard?

  3. Pollig-Hellman • Useful when (p-1) has only small prime factors • Did long derivation • Introduced problem 2x=12 (mod 19) • This will be part of Homework 7.

  4. Baby Step, Giant Step Like the meet-in-the-middle attack on Double-DES Eve chooses , say She makes 2 tables: and looks for a match. Why should there be one? Write x in base N. Requires ~p comparisons, but only p1/2 exponentiations and space. Works for medium-size primes.

  5. Some things we won’t cover in class about Discrete Logs • 7.2.3 Index Calculus: like sieve method of factoring primes • The equation on p. 207 might help with some of homework 7. • Discrete logs mod 4 and bit commitment • We skip to make time for the quiz (today) and for some of the applications of discrete logs (tomorrow) • Although the football game prediction analogy is interesting…

  6. Quick humor before the quiz • http://xkcd.com/c247.html • Thanks to Ted Lyman

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