What do I need to restore an encrypted MSSQL database?
We can't restore a backup on a different instance without Certificates. We have to restore the Cert from the source server, then we should be able to restore the database from the backup.

Obviously your certificate &amp; master key are required for restore.

As MSSQLTREK Blog here To restore the Certificate from source (and you have to create a DMK (Database Master Key) on destination if you don’t have one), the rest is just performing your normal DB restore process what you do on any other non encrypted user database(s). 

Create a Master Key (you don’t have to do this if you already have DMK) and create a certificate from the cert backup and provide private Key file and password to decrypt it.


  Backup files of databases that have TDE enabled are also encrypted by
  using the database encryption key. As a result, when you restore these
  backups, the certificate protecting the database encryption key must
  be available. This means that in addition to backing up the database,
  you have to make sure that you maintain backups of the server
  certificates to prevent data loss. Data loss will result if the
  certificate is no longer available.


For your further ref Here and Here

Note : If you enable TDE on any Database on your Instance, Your TEMPDB is automatically Encrypted as well. So there’s a high possibility impacting other databases which are actually not using TDE feature while you are in the process of enabling TDE!