I've the same issue still going on.. At this stage, we just want to provide our clients with what they will need to do when the master key gets corrupted.. So for testing this, I'm restored our database(UMP) to test. I took a backup of the master key from the UMP database.

use UMP

BACKUP MASTER KEY TO FILE = 'd:\ump\umpkey'

ENCRYPTION BY PASSWORD = '123'

Now, on the test database the decryption works perfect. I tried below to corrupt the master key:

OPEN MASTER KEY DECRYPTION BY PASSWORD = '239kc5i4gt6j81mn3k';

ALTER MASTER KEY

REGENERATE WITH ENCRYPTION BY PASSWORD = 'tst';

Now tried to decrypt the existing records, since the master key is altered- I expect the decryption not to work. But it decrypts successfully. Is there any other way to test our situation? We just want to test if the backup and restore of the master key will work incase of lost master key or corrupt master key so we can provide the steps to the client.

Thanks again for your help.