Which term describes evaluating a known function without revealing the parties' inputs when the function is public?

• A. Public Function Evaluation
• B. Private Information Retrieval (PIR)
• C. Homomorphic Encryption
• D. Secure Function Evaluation (SFE)

Answer: (D)

Evaluating a known function while keeping each party’s inputs private is about privacy-preserving joint computation. Secure Function Evaluation describes protocols that let multiple parties compute the value of a function they all know, without revealing their private inputs to one another. Even when the function itself is public, SFE ensures that the inputs remain confidential throughout the calculation and that the correct output is obtained. Techniques like garbled circuits or secret-sharing-based protocols are common ways to implement SFE, enabling the secure collaboration needed for this scenario.

The other concepts don’t fit as well. PIR is about retrieving data from a database without revealing the query, not about jointly computing a function with private inputs. Homomorphic encryption allows performing computations on encrypted data, but by itself it doesn’t guarantee the broader privacy guarantees across all parties during the joint computation. Public Function Evaluation isn’t a standard term used for this cryptographic goal.