Maish Saidel-Keesing lays out how to configure SSD Equivalence for Oracle RAC at technodrone.blogspot.com:

There are a number of posts on how to do this like here or here, and Oracle even have been so kind as to provide a script that will do this for you (even though it is not 100% automated.

Read more at: Configuring SSH Equivalence for Oracle RAC