Thanks for the reply.
In my case, I have a web development in php where users are created using the password encryption function ("password_hash").
For communication with mobile devices I have a web service developed in java.
It sounds logical that you send the user and password to the web service (in java) and that it validates the password hash.
In php, the "password_verify" function is used to compare the password against its hash equivalent.
Do you know of any api in java that does the right thing?