FIELD: computer engineering. SUBSTANCE: data transmission system formed by at least one terminal and at least one portable data medium, such as integrated-circuit card which is, essentially, monetary value, has area of nonvolatile memory (NVM) of card divided into two value areas (WBA, WBB) of which only one (WBA or, respectively, WBB) is invoked irrespective of power supply while other one (WBB or, respectively, WBA) may be invoked for the time being only. During card recharging new state of counter is first entered only in pre-invoked value area (WBB) and only after correct entry is checked, this area (WBB) may be invoked irrespective of power supply. EFFECT: eliminated abuse of data. 8 cl, 1 dwg
