Method for the functioning of a chip card, and chip card in accordance therewith

A method of operating a chip card having first and second states, comprising the steps of

• providing a first indicator, the first indicator defining the state of the chip card such that the first indicator is set at a first state value when the chip card is in a first state and is set at a second state value when the chip card is in a second state, and wherein certain functions are permitted to be performed when the chip card is in the first state and are not permitted to be performed when the chip card is in the second state;
• providing a second indicator, the second indicator defining a right to return to the first state of the chip card, the right existing when the second indicator is at a first value and the right not existing when the second indicator is at a second value, and wherein the value of the second indicator is determined based upon whether an invalid return instruction has been received;
• advancing the chip card from the first state to the second state, and as a result changing the value of the first indicator from the first state value to the second state value;
• receiving a return instruction at the chip card;
• ascertaining whether the return instruction is valid and ascertaining whether the second indicator is at the first value,
• and, if the return instruction is valid and the second indicator is at the first value, then returning the chip card to the first state,
• and, if the rerun instruction is valid but the second indicator is not at the first value, then not returning the chip card to the first state,
• and, if the second indicator is at the first value but the return instruction is not valid, then not returning the chip card to the first state,
• and, if the return instruction is not valid and the second indicator is not at the first value, then setting the second indicator to the second value and not returning the chip card to the first state.

A chip card comprising

• a first indicator means for defining the state of the chip card, wherein certain functions are permitted to be performed when the chip card is in a first state and are not permitted to be performed when the chip card is in a second state;
• a second indicator means for defining a right to return to a previous state of the chip card, the right existing when the second indicator is at a first value and the right not existing when the second indicator is at a second value, and wherein the value of the second indicator is determined based upon whether an invalid return instruction has been received;
• means for ascertaining whether a return instruction received at the chip card is valid and means for ascertaining whether the second indicator is at the first value,
• said ascertaining means returning the chip card to the first state if the return instruction is valid and the second indicator is at the first value,
• said ascertaining means not returning the chip card to the first state if the return instruction is valid but the second indicator is not at the first value,
• said ascertaining means permanently preventing the chip card from returning to the first state by permanently setting the second indicator to the second value if the second indicator is at the first value but the return instruction is not valid, and
• said ascertaining means permanently preventing the chip card from returning to the first state by permanently setting the second indicator to the second value if the return instruction is not valid and the second indicator is not at the first value.