Within a customer security environment, customers can take usernames for end-users, hash them (create a cryptographic one-way modification), and then take half of those hashes as a zero-knowledge way of identifying users. HackNotice brings in billions of credentials from leaks, extracts usernames, and builds the same hash by matching each customer’s half-hash to the customer’s full-hash. HackNotice identifies each hash and password pair that can be used to protect clients. HackNotice provides the half-hash pairs to customers, which customers can reverse. HackNotice then provides the half-hashes and password pairs to customers to turn into user pairs. These user credentials are then verified as working credentials and if they are matched, credentials should be reset.