Secrecy and Symmetric Key Ciphers

Goals

• Gain high-level intuition for how PRPs are constructed
• Define basic security for encryption via the IND-CPA security game
• Prove basic criteria necessary for IND-CPA security

Block Ciphers

• How are PRPs and block ciphers related?
• What are some examples of block ciphers?
• Should DES (or 3DES) be used today?
• At a high-level, how does AES work?
• What are some examples of way to attack block ciphers?

Semantic Security

• How is semantic security defined?
• Does IND-CPA imply security against plaintext recovery?
• Does IND-CPA imply security against key recovery?
• What are two simple tests that can tell you an encryption scheme is NOT IND-CPA secure?