What do you mean by that? If you scramble the keys as they enter the input system then you can't write anything. If you want the user to be able to use use the keyboard then you can also read what's getting sent to userspace.
For the pedants:
Some more advanced antiloggers are minus ring-0 and physically remap the keys so that `A` doesn't mean A at all. Infact if I typed this, a load of garbage would be displayed on the screen. The only reason we see valid output is because of a software abstraction layer translating the 'garbage' back to it original symbolic meaning. This is how we thwart such a kernel logger as described in this thread.