1. A method comprising: causing, at least in part, transmission of a query associated with a first user, the first user being described according to a first set of criteria; and based, at least in part, on the query, receiving one or more second sets of criteria associated with respective second users, wherein the second sets of criteria are matched, at least in part, to the first set of criteria, and wherein at least one of the second sets of criteria is used as a public key for encrypting data according to an identity-based encryption scheme.