This dialog combines the following commands: Protect archive, creating recovery volumes, Lock archive and "Sign archive". All they are supported only by RAR archive format.
Protecting an archive may help to repair it later in case of small physical damage of the archive data. If you wish to protect an archive from damage, you need to specify a size of the recovery record in percent to the total archive size. The maximum allowed value is 10%, if you set this field to 0, the recovery record will not be added. Larger recovery record allows to recover from more serious damages, but at the same time it increases archive size, so 1 - 3% is probably optimal.
The special case of archive protecting is generating recovery volumes. It is possible only if an opened archive is the first file in the multivolume sequence, in this case you just need to select the number of .rev files to create. You may also append a percent character to this parameter, in such case the number of creating .rev files will be equal to this percent taken from the total number of RAR volumes. Each recovery volume allows to reconstruct one missing volume file. You may read more about this feature here.
If you set "Disable archive modifications" option, an archive will be locked. It means that WinRAR will not be able to modify such archive in future. You may lock important archives to prevent accidental modification by WinRAR.
Next option, "Add authenticity information", is avaliable only to registered users and forces WinRAR to put in archive information concerning the creator, last update time and archive name. In archive management mode it is always possible to read the authenticity information using the Show information command.