It is VERY IMPORTANT to keep your encryption key in a safe place! If you lose your encrypting key, you will not be able to restore your backup files.
For maximum security, choose "Custom", select AES (Advanced Encryption Standard) Algorithm, CBC (Cipher Block Chaining) mode, and create an encrypting key with more than 8 characters.
You will have two options when creating your encryption key: The first is "Default". Choosing this option simply uses the software client password (password you used to log in to the software when you lauched it) as your encryption key. We recommend against choosing "Default" because even if the software client password is changed afterward, the encrypting key would stay the same. The second option is to create a new/separate key for the backup set. This is the recommended approach.