Lecture 5: IND-CPA, OTP and Block Ciphers
Intro to Cryptography
(True/False) Cryptography only reasons about defending against known attacks
(True/False) One difference between symmetric and asymmetric key cryptography is that in the former one key is held by both parties, while in the latter both parties have different keys
Kerckhoff’s Principle/Security Through Obscurity
What are three reasons cryptographic schemes should be public? Which part of a cryptosystem must be kept private?
Intro to Symmetric Encryption Schemes
Why do we allow the ciphertext to leak the length of the message in our definition of confidentiality?
Defining Security for Symmetric Encryption
What did our original idea of security fail to account for?
Security Games and IND-CPA
What is the adversary's goal in the IND-CPA game?
Is Enc(K, M) = 3*K +2*M, IND-CPA secure?
If we modify IND-CPA such that the messages sent in the challenge phase can't be queried during either of the query phases, which type of undesirable encryption scheme will now be considered IND-CPA?
Consider a variant of IND-CPA, IND-CPA', where an attack can only make one query before submitting their challenge and no queries after. Is the OTP IND-CPA' secure?