Patent ID: 7707621

Claim:
A method of attempting a write to a target entity having first and second security fields to cause the target entity to perform an action, the method including the steps of: initializing the first security field with a first initial value and the second security field with a second initial value; sending a first message to the target entity that is an integrated circuit, the first message being configured to cause the entity to perform the action and to adjust the first and second initial values in the first and second security fields by respective first and second amounts resulting in respective first and second adjusted values; sending a second message to the target entity, the second message being configured to cause the entity to adjust the first and second initial values in the first and second security fields by respective third and fourth amounts resulting in respective third and fourth adjusted values; wherein the security fields have write restrictions associated with them which prevent values in the security fields being adjusted: in accordance with the first message, if the initial values have been adjusted in accordance with the second message; and in accordance with the second message, if the initial values have been adjusted in accordance with the first message, and wherein the action is only performed when the initial values in the security fields have been adjusted in accordance with the first message, and the first and second adjusted values are different than the third and fourth adjusted values, respectively.