The IRMA app showcases attribute based authentication.
The app allows you to obtain signed statements about yourself (attributes) which are stored only on your phone and nowhere else.
These attributes can be relevant properties, such as: 'I am over 18', 'my name is ...' and 'I am entitled to access ....'.
You can use any subset of your attributes to authenticate to services.
IRMA offers a privacy-friendly, flexible and secure solution to many authentication problems, putting the user in full control over his/her data.
Find out more details at: https://www.irmacard.org/irmaphone/
The code of this app is available as open-source on: https://github.com/credentials