Comment 12 for bug 139057

@Luke

I don't know the internals of the shell...
Maybe a function like this will help:

unset_pass()
{
        [ -n "$1" ] || return 0
        eval "$1=\$(dd if=/dev/urandom bs=1k count=4 2>/dev/null)"
        unset $1
        return 0
}

unset_pass PASS