a method is provided for authenticating debit card transactions engaged in by a cardholder on a communications network . the method includes : a ) establishing a connection over the network with a client being used by the cardholder to engage in a transaction on the network ; b ) providing over the connection to the client a web page containing a keypad having a plurality of buttons that collectively define a geometry of the keypad , the keypad being employed by the cardholder to enter a pin via selection of the buttons with a pointing device of the client ; c ) obtaining over the connection the pin enter by the cardholder ; d ) determining if the obtained pin is correct for a debit card being used by the cardholder to engage in the transaction ; e ) repeating step a ) through d ) for each transaction the cardholder engages in on the network ; and , f ) with respect to two transactions engaged in by the cardholder , changing at least one of a location of the keypad on the web page , the geometry of the keypad , a size of the buttons and a spacing between neighboring buttons .