Netbackup Catalog Restore 8.1.2

The steps would be to follow the process outlined in the Disaster Recovery section of the troubleshooting guide.

1. Rebuild master server to same NetBackup version (and same name).
2. Since you have encrypted tapes (you don't say how) but if via KMS, then you will need to recreate the KMS keys to enable the tape to be read (as long as you have the various passphrases you should be good). 
3. Perform a catalog recovery
4. Recover the CA certificate for the master server using the DR package (this can also be done during the initial build of the new master server). 

If you are unable to recover the catalog tape (by the way, it is not recommended to encrypt the catalog backups), then you will have to try recovering the MSDP pool to the newly built master. There's a good article from our friend Marianne where she decribes this process - see https://vox.veritas.com/t5/NetBackup/Import-MSDP-images/m-p/462337.

I would be reaching out to Veritas support in either case to assist with which ever process you go with.

I saw this post on Saturday and thought to myself - 'this is where angels fear to tread...'

As per davidmoline  - you never said what type of encryption was used. 
We can only hope that have documented your encryption process and most important - how to recover encrytion keys in case of a disaster? 

To recover from tape on Appliance - you need to complete basic steps to add the Appliance as media server and configure tape devices and adding the catalog tape in the library (inventory). These steps will be documented in the email notification that you have (hopefully) configured as part of catalog backup config. 
Successful catalog recovery will restore the MSDP config on the master server.

You will see in my 'MSDP import' post that we had no catalog backup - MSDP import was the only way that we could recover.