Just a note about filexor/filerot/filecrypt because the current quickbms.txt documentation lacks the FILENUM field after OFFSET:
filexor VAR [OFFSET] [FILENUM]
filexor is a command that works universally on all the files, that FILENUM is ONLY referred to the optional OFFSET field since it's used to calculate the position in the key you are using depending by the offset of the file.
Now there is a very rare event (happened yesterday) in which you may need to use a MEMORY_FILE or a file different than the main one (0) and after you set OFFSET you notice that the decryption is a mess... that's caused by the missing FILENUM field which is mandatory in this rare situation, example:
savepos CURRENT_OFFSET MEMORY_FILE
filexor KEY CURRENT_OFFSET MEMORY_FILE
get VAR long MEMORY_FILE
Don't think that being the author of quickbms makes me remember all the commands, options, features, caveats and bugs of the tool
I check quickbms.txt and even the source code of quickbms (damn "encryption random"...) very often...