### Questions (8)

 7 Difference left-or-right CPA security, IND-CPA security 4 Construct IND-CPA secure encryption scheme by combining two given schemes 3 Encrypt-then-authenticate variant used in IPsec 3 Given a pseudorandom function F, is $(F_k(r) \; | \; F_k(r + 1))$ also a PRF? 3 Are parts of a pseudorandom string also a pseudorandom string?

### Reputation (246)

 +5 Construct IND-CPA secure encryption scheme by combining two given schemes +25 Difference left-or-right CPA security, IND-CPA security +5 Given a pseudorandom function F, is $(F_k(r) \; | \; F_k(r + 1))$ also a PRF? +5 Why is $Mac_k(m_1||m_2) = ⟨F_k(m_1), F_k(m_1 \oplus \overline{m_2})⟩$ not a secure MAC?

 1 Determine whether a given function is a pseudorandom generator/function

### Tags (12)

 1 pseudo-random-function × 5 0 provable-security × 3 1 pseudo-random-generator × 4 0 mac × 2 0 chosen-plaintext-attack × 5 0 authenticated-encryption 0 encryption × 4 0 authentication 0 ciphertext-only-attack × 3 0 protocol-design