How to verify that encryption passwords are correct and valid on LiteSpeed backup files, before moving files to permanent storage?
1. xp_restore_checkpassword @filename='pathtofilehere', @encryptionkey='password_here'.
When the correct password is supplied, the message "Encryption key matched successfully" is returned.
2. xp_restore_verifyonly @filename='pathtofilehere', @encryptionkey='password_here'
or xp_restore_headeronly @filename='pathtofilehere', @encryptionkey='password_here'
When the correct password is supplied, the message "The backup set is valid." is returned.
3. Servers that are licensed with a Professional license key, access Object Level Recovery via the Enterprise Console, as you move through the GUI screens, the LiteSpeed application asks for the encryption password before it even builds the .lsm file (which can be the time-consuming part of OLR). This is an indirect way to check passwords, but substantially quicker than xp_verifyonly.
LiteSpeed uses a combination of public and private encryption keys (and one key is actually encrypted by the other). It is highly improbable that anyone could unencrypt the backup file without a valid key (even Quest Software, Inc.)
For additional information, see: https://technet.microsoft.com/library/Cc966442