Question

Freedman-Nissim-Pinkas Protocol not always correct. Explain briefly why

Answer 1

A brief explanation about the reason why Freedman-Nissim-Pinkas protocol is not always correct:

It looks like the protocol is to do with a private set intersection. The concept of Chosen-Ciphertext Attack (CCA) security is applied only to encryption schemes. Also, the protocol's solution or the protocol for a shared version requires a secure circuit evaluation. Whereas, with respect to the computation of the set intersection cardinality task, equivalent to privately computing the scalar product of two binary vectors, in the non-shared case, the protocol lets the participants too to learn the values as such the protocol lets for any information learned by all the participating parties to be sent in the clear.

Also, the problem is permanent in the security definitions both, for semi-honest and malicious parties, as they only consider the parties “formally” participate in the protocol.