restore database with decryption

Hello,

I am testing out an rman backup database process where I have added an encryption line.  For example, set encryption on identified by 'blah1';  The backup process seems to be fine; however, when I try to restore I am getting a ORA-19610: directory block 1 is corrupt failover to previous backup.  I have done the steps below.  Any information would be appreciated. 

1. startup mount;

2. set decryption identified by 'blah1';

3. restore database validate;

4. restore database;