In Peppermint, each user of a tenant received a special code that is stored, when the user responds to the initial invitation, in the user storage. Each of the 3 supported methods,  returns  that unique secure token.

To login, enter the following address in your internet browser :

When you login again (choosing a method and entering valid credentials), the login process will return a token, that has to match the one that is stored by Peppermint in the user storage.

Login will be successful if the tokens match.