Patent ID: 8353054

Claim:
A method for protecting a chip card from unauthorized use, comprising the following steps: a first identifier is input into a chip card terminal, a cipher is produced from at least one first communication parameter using a first symmetric key derived from the first identifier, wherein the communication parameter can be used to define a protected first communication channel between the chip card terminal and the chip card, the cipher is transmitted via a predefined communication channel from the chip card terminal to the chip card, an attempt is made to decrypt the cipher using a second symmetric key by the chip card, the result of the decryption being the first communication parameter only if the first symmetric key is the same as the second symmetric key, so that the protected first communication channel can be defined between the chip card terminal and the chip card only if the first identifier is correct, wherein the first communication parameter is the specification of a transmission frequency, of a frequency hopping scheme, of a coding method and/or of a modulation method, and wherein the first communication parameter is a first domain parameter for the performance of a discrete logarithmic cryptographic method for the production of a third symmetric key by the chip card terminal of a fourth symmetric key by the chip card and, wherein the third and fourth keys are identical if the first identifier is correct, wherein the third and fourth symmetric keys are provided for the purpose of encrypting the communication between the chip card terminal and the chip card via the protected first communication channel.