Securing a file with UBX is like burying treasure in an infinitely thick vault that can be opened only with the correct password. UBX 1600-bit symmetric data encryption was already an unbreakable vault. Now UBX is 8800-bit for your peace of mind.
All characters and all symbols from all languages are permitted in passwords and in hints. If you can type it, you can make it your password. Get creative, but don't get carried away. There's no password recovery or "backdoor" or master key, so don't forget the password.
The core, the heart, the main attraction of UBX is the jumble. The stream cipher randomizes the file contents, and then the jumble cipher randomizes the order of the contents. Thanks to its huge block size (up to 128MB) and slow speed, the jumble cipher is the ideal method of encryption for archived data.
A key file of sufficient size is akin to a monstrously long password, too long for any normal mind to recall. The maximum lengths are 510 bytes for passwords and 65536 bytes (64KB) for key files. Any file can be a key file.
For online backups I use UBX as an extra protection on top of standard AES. I heard from an "expert" that AI could break AES-256. So now when backing up certain things online I compress my files in 7z with AES-256, and then I put that 7z archive in UBX with a different password. Always use a different password!