A public key generated by each user of a plurality of users is used to encrypt the contacts for that user. The results are sent to a server by each user. The key generated by each user is then distributed to every other user in the system, and each recipient encrypts their contacts with the keys. The result of these encryptions for all contacts for all recipients is then received by the server, and the server computes an encrypted computation of equality of two contacts and sends all computations back to the original user. The user can use the homomorphic property of the crypto protocol (e.g., a private key) to determine a set of users that are matched as contacts with the other users. The binary results are returned to the server, and the server computes a graph using the results.