Troy hunt created a service for this. He provides an API where you can securely check if a user's password is pwned without revealing the password to his server

Troy hunt created a service for this. He provides an API where you can securely check if a user's password is pwned without revealing the password to his server. He's written about it several times, here's one of the posts: https://www.troyhunt.com/enhancing-pwned-passwords-privacy-by-exclusively-supporting-anonymity/ https://www.troyhunt.com/enhancing-pwned-passwords-privacy-b...