In some embodiments, the present disclosure provides various techniques for authenticating stack(s) of cards, for example, during a change of their custody, by printing at least one unique pattern across at least one side of a stack of cards at a first point in time; recording the pattern as printed on the stack of cards; and comparing the pattern shown on the stack of cards at a later point in time to the originally recorded pattern and confirming the presence or absence of change(s) to such pattern. In some embodiments, the present disclosure also provides various techniques to validate a particular card within the stack of cards by comparing at least one side edge of a card in the stack that comprises a portion of the unique pattern that was printed across the side of the parent stack from which it belongs to a prior recorded image of the printed pattern on that particular parent stack and confirming that the information or markings on the at least one side edge of the card is a component of the unique pattern that was printed on the at least one side of its parent stack.