Cryptography and Security

Winter 2020 at ENS Lyon

General information

This course is an introduction to modern cryptography.


For some online resources on probability (for computer science), you can look at these notes.


The grading scheme will take into account


Date Topic References
Jan 15th Introduction. Perfect security. One-time pad. Shannon's theorem: Secret key must be long.
Relaxing perfect secrecy: stream ciphers and pseudo-random generators.
Ch 2 and 3 of [BS], Ch 1 and 2 of [KL]
Jan 22nd Pseudo-random generetors. Security of a PRG. Unpredictability of a PRG. Equivalence between security and unpredictability.
Semantic security for ciphers (for one-time key and chosen plaintext)
Ch 2 and 3 of [BS], Ch 3 of [KL]
Jan 29th Semantic security for stream ciphers. Pseudo-random functions, construction from PRG. Block ciphers (or PRPs). Brief overview of DES and AES. Encryption with block cipher (deterministic counter mode). Ch 4 of [BS]
Feb 5th CPA security. Randomized countermode is CPA secure. Message authentication codes. Ch 5 and 6 of [BS]
Feb 12th Message authentication codes from PRF. Signing longer messages with CBC-MAC. Authenticated encryption. Ch 6 and 9 of [BS]