1. A method of performing an authentication operation, the method comprising: receiving an electronic input signal from an electronic input device to take current pulse data from a user; performing a comparison between the current pulse data from the user and expected pulse data for the user; and generating an authentication result based on the comparison between the current pulse data and the expected pulse data, the authentication result being constructed and arranged to control user access to a computerized resource; wherein performing the comparison between the current pulse data from the user and the expected pulse data for the user includes: retrieving previously obtained cardiac pulse data of the user from a cardiac pulse waveform database which stores multiple pulse data entries, each pulse data entry including (i) pulse data and (ii) a timestamp, identifying a set of pulse waveform adjustments from the pulse data entries, and generating, as at least part of the expected pulse data, measurements of an expected cardiac pulse waveform for the user based on (i) pulse data of particular pulse data entries stored in the cardiac pulse waveform database, (ii) the set of pulse waveform adjustments, and (iii) current time information.