A method of generating a verification code includes measuring a time of arrival and a corresponding first or second state value of a plurality of first photons and a plurality of second photons, where respective ones of the plurality of first photons are entangled with respective ones of a plurality of second photons in a first basis, which is time, and entangled in a second basis. A first and a second ordered list of the measured times of arrival of the plurality of respective first and second photons is generated. Time-of-arrival matches between the first ordered list and the second ordered list are determined. First or second state values that correspond to the determined time-of-arrival matches between the first ordered list and the second ordered list are determined. A verification code using some of the determined first or second state values that correspond to the determined time-of-arrival matches is generated.