Week 2

Lecture 2 (01/29/08, Tu): We covered some general terms related to security, such as
various attack models (chosen plaintext/ciphertext). We discussed various classical
ciphers. We covered one-time-pad and how they can be made practical using psuedo-random
number generators (PRGs). We spend some time on the Blum-Blum-Shub (BBS) PRG. More
information about the BBS generator can be found in the handbook (which is linked to
the class web-page).

Lecture 3 (01/31/08, Th): We covered linear feedback shift registers (LFSRs) and showed
a known plaintext attack on it (the attack was based on the linear relationship between
the bits of the keystream). We discussed one way to break the non-linearity (called the
Geffe generator). We discussed Fiestel cipher, which is a general way to build block ciphers.

Week 1

Tu (01/22/08): We discussed the organization of the class. For example, we discussed various security primitives (encryption, hashing, signatures) and functionality provided by them. Then
we discussed how these primitives can be composed to construct services (such as SSL and
Kerberos). We also discussed logistics and schedule of the class.

Th (01/24/08): Instructor was out of town.