The protocol helps clients check whether a specific identifier is present in a list held by a server, in a privacy-preserving manner: the client identifier is transmitted encrypted, the server doesn’t learn the result of the query, and the client doesn’t learn details on the set of identifiers on the server, other than whether the queried identifier is or isn’t a member of the set.
“As an example, users may want to check membership of a computer program on a block list consisting of known malicious software before executing the program. Often, the set’s contents and the queried items are sensitive, so we designed Private Set Membership to perform this task while preserving the privacy of our users,” Google explains.
