To generate random wireless passwords on linux the following shell command might come handy. It prints to stdout a random string of hexadecimal digits taken from /dev/random. Consider that it might take a while because /dev/random might not contain enough entropy (mouse movements, disk and network activity are all sources of entropy).
xxd -l [length] -c [length] -p /dev/random
is the length in bytes of the random password; the following are the key lengths for various encryption standards:
If you don't have a linux shell available, you can use the following page to generate random wi-fi passwords online.