You can find material on the syntax of Chor in Chapter 7 of: http://fabriziomontesi.com/files/m13_phdthesis.pdf

# Exercise 1
- Download openid.cho.
- Write a choreography (in the main procedure) that implements the protocol OpenID.

## Tip 1: Use ask and show to get username and password from the user, and to ask at the identity provider
whether the username/password combination is correct, e.g.,
ask@ip( "Is the username/password combination correct? " + username + "/" + password, decision )

## Tip 2: Use the conditional construct if-then-else at the identity provider, e.g.,
if ( decision == "yes" )@ip { ... } else { ... }


# Exercise 2
Modify the program you obtain from exercise 1 such that:
- the identity provider opens another session with a logger;
- the identity provider sends to the logger a message on whether the user was successfully authenticated or not.
- [optional] reuse the logger code from the exercises of the previous lecture to write logs in a file.