passing login paramters from php web application to asp web application. help.

Dear friends, we have a peculiar problem here. Our customer log in in our customer relationship management application using a unique if, unique password. We use php with mysql. We have a partnership with a company which has a crm application developed in asp, sqlserver. The same customer log in in their crm using a different pair of unique login, unique password. We would like to allow the customer to log in our crm (php, mysql), then pass the parameter on automatically so that they can see also this part of the crm of the partner (asp, sqlserver) which is of common interest, without having to log in again. Do you have a solution for this problem? Thank you in advance.