A password is information that you "know" not something you "have." I believe that giving a password is testifying information. This appears to be the sticking

A password is information that you "know" not something you "have." I believe that giving a password is testifying information. This appears to be the sticking point. He is being locked up for refusing to say the equivalent of a word that would be information used against him. To me, that is being locked up for refusing to testify. Locking up for refusing is compelling. Therefore he is being compelled to testify.