This attack does require that the PIN to the card be known, so that many private key operations can be performed on chosen input bytes. Physical attacks Physical attacks occur when normal physical conditions, such as temperature, clock frequency, voltage, etc, are altered in order to gain access to sensitive information on the smartcard. Other physical attacks that have proven to be successful involve an intense physical fluctuation at the precise time and location where the PIN verification takes place. Thus, sensitive card functions can be performed even though the PIN is unknown. This type of attack can be combined with the logical attack mentioned above in order to gain knowledge of the private key.
Most physical attacks require special equipment.
This attack involves a rogue, Trojan horse application that has been planted on an unsuspecting user s workstation. The Trojan horse waits until the user submits a valid PIN from a trusted application, thus enabling usage of the private key, and then asks the smartcard to digitally sign some rogue data. The operation completes but the user never knows that their private key was just used against their will. This prevents the attack but also lessens the convenience of the smartcard because multiple applications can not use the services of the card at the same time. In this model, the user must enter their PIN every single time the private key is to be used and therefore the Trojan horse would not have access to the key.