Semantic Security
Semantic security, introduced by Goldwasser and Micali, means an attacker cannot compute any efficiently computable predicate of the plaintext from the ciphertext — the formalization of the information-theoretic intuition of confidentiality.
Purpose
It defines the "no information leakage" standard of encryption confidentiality and is equivalent to IND-CPA (for symmetric/public-key encryption).
Mechanism
The adversary has prior knowledge of the plaintext distribution and, after seeing the ciphertext, tries to compute some predicate f(m) with no more advantage than without the ciphertext, up to a negligible amount. Semantic security ⟺ IND-CPA.
Use cases
- Encryption security definitions
- Provable security
- Formalizing confidentiality