A computer-implemented method comprises, storing user identity records in digital data repositories relating to user identity information collected from a plurality of sources, receiving a request specifying a partial hash of particular user identity information, generating and submitting a query to the digital data repositories to retrieve a set of user identity records that match the partial hash, generating and storing a bloom filter based on the plurality of user credential values associated with the particular user identity information, the bloom filter being configured to allow a client computing device to determine whether a particular user credential value that is associated with the particular user identity information is included in the plurality of user credentials represented by the bloom filter, transmitting the bloom filter to the client computing device.