What is the growlnotify -c option?

Question

If growlnotify -h:

Usage: growlnotify [-hsvuwc] [-i ext] [-I filepath] [--image filepath]
                   [-a appname] [-p priority] [-H host] [-P password]
                   [-n name] [-A method] [--html] [-m message] [-t] [--url url]
                   [title]

But the meaning of c in [-hsvuwc] is not described. What could it be?

Update:

the official man page installed with the program has no description of a c option. Several online man pages I found has neither.

Answer 1

From the man page:

-c,--crypt      Encrypt UDP notifications. By default, UDP notifications are sent unencrypted.

Answer 2

-c,--crypt Encrypt UDP notifications.

per growlnotify -h on my install.