When using encryption, you will be prompted for a default pass-phrase whenever you try to read the archive. This will temporarily get stored in a file unreadable for others. If you leave it empty, pgp(1) will prompt you for the pass-phrase again and again with every singe file it decrypts. Please, do read the pgp(1) manual page and documentation before using it!
There is also a problem with old versions of afio(1) and pgp(1) : If the encrypted file is bigger than the original one, current versions of afio(1) will store it unencrypted! So check your logfiles carefully when using encryption. Please use at least afio(1) version 2.4.2 when using encryption.
For legal reasons, I cannot include pgp(1) with KBACKUP . Its several versions are available from ftp-servers all over the world, e.g. from ftp.th-darmstadt.de.