A human interaction component must be addressed for this to work. By changing the angle of the signal or attaching a binary depending on either the keypad numbers pressed or a random number pressed. The new attached binary or hash must equal ones assigned or in the database for the signal to continue. I say angle because if binary encoding is not possible, you can get the angle of the binary and if it matches an angle for supported binaries then it can go through.
This should be easy to employ and of limited overhead. It is similar to what banks use.
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