Abstract: A method comprises: generating a first partial hash of the user identity information, transmitting a first query to a server computer, in response to transmitting the first query, receiving query metrics that indicate a set of counts of expected results, determining whether a count of expected results of the first partial hash satisfies a threshold count of expected results, in response to determining that the count of expected results of the first partial hash satisfies the threshold: generating and transmitting a second query, and in response, receiving and storing a set of user identity records that match at least the first partial hash, querying the set of user identity records using the user identity information and in response, receiving a result set of user identity records, the result set of user identity records comprising one or more user identity records that match the user identity information.

Abstract: 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.