Method for protecting a chip card against unauthorised use, chip card and chip cards terminal

Description

[0001] The invention relates to a method of protecting a smart card against unauthorized use, a smart card and a processor card terminal.

In order to activate the functions of the smart cards, it may be necessary to identify the user in advance with the smart card as is known in the art. The most common form of user identification is the entry of a secret identifier, generally known as a PIN (personal Identification number) or CHV (card holder verification) code. Such identifiers generally consist of a string of numeric or alphanumeric characters. In order to identify the user, this identifier is entered by the user by means of a keyboard into a terminal for smart cards or to a computer to which the smart card reader is connected, and then it is sent to the chip card. This compares the entered identifier with the stored identifier, and then communicates the result to the terminal or computer by issuing an appropriate signal.

[0003] For PINs, a distinction is made between static and variable PINs. The static PIN can no longer be changed by the user and must be memorized. If someone finds out about it, the user of the smart card must destroy it to prevent unauthorized use by an unauthorized person and try to get a new smart card with a different static PIN code. The user also needs a new smart card if he forgets the static PIN code.

[0004] A variable PIN is freely changeable by the user. In order to change the PIN, for security reasons, it is still necessary to enter the current PIN, as otherwise any existing PIN could be replaced by the attacker with his own code.

[0005] This is not the case with the so-called super-PIN or PUK (personal unlocking key) codes. They generally have more characters than the correct PIN and are used to reset the incorrect PIN input count (also known as a "misuse counter") set to the maximum value. Using the PUK code, a new PIN is also transferred to the smart card, because the withdrawn incorrect handling counter will not help if the user has forgotten the PIN code. This is most often the case when the malfunction counter reaches its maximum value.

[0006] There are also applications that use a transport PIN. The chip card is personalized with a random PIN code, which the card user receives in the letter with the PIN code. During the first entry, the smart card will ask the user to replace the personalized PIN with his own code. In a similar method, called the "zero PIN" method, the smart card is pre-provided with a trivial PIN such as "0000" and on first use the smart card also forces a change (cf. also DE 35 23 237 A1, DE 195 07 043 A1, DE 195 07 044 C2, DE 198 50 307 C2, EP 0 730 253 B1). Such a method provides a so-called first user function which gives the authorized user the assurance that prior to his first use by him no unauthorized use of the smart card has taken place.

[0007] From DE 198 50 307 C2 a method of protection against unauthorized use of smart cards is known. The chip card has a first user function that, on first use of the data and / or functions of the smart card, requires a user-selectable personal code (PIN), whereby by entering a personal code the data and / or functions of the smart card are entered into a status of use. The master unlock code allows you to change the personal code later.

[0008] There are already known methods of checking an identifier in which it is not necessary to transmit the identifier itself, such as the Strong PasswordOnly Authenticated Key Exchange (SPEKE) method, the Encripted Key Exchange method based on the Diffie-Hellman protocol (DH-EKE). , Bellovin-Merritt protocol or Password Authenticated Connection Establishment (PACE) method. The SPEKE protocol is known, for example, from www.jablon.org/speke97.html, US 6,792,533 B2 and US 7,139,917 B2. The DH-EKE protocol is also known from the website www.jablon.org/speke97.html. The Bellovin-Merritt protocol is known from, inter alia, US 5,241,599. The PACE protocol is known from the website www.heise.de/se- curity / news / meldung / 85024 and is particularly suitable for elliptic curve cryptography.

[0009] A general overview of the basics of symmetric encryption can be found, for example, in the document "Applied Cryptography" by Bruce Schneier (1996), published by John Wiley and Sons.

[0010] Furthermore, the document "Kryptographie und elliptische Kurven" by Christian Hainz (2001-04-01, pages 2-14) gives a general overview of the use of elliptic curves in cryptography, for example in the context of the key exchange method based on the Diffie-Hellman protocol.

[0011] Document DE 103 38 643 A1 discloses a method for reliably identifying an object, which can be used for example for self-foreign identification. For this purpose, the sending frequencies used for transmitting the sequence of submessages are changed, the frequency series used being determined by one participant and communicated to the other participant in a secure manner.

Document DE 198 50 308 A1 further describes a method for securing smart cards against unauthorized use in third-party devices. In the context of the challenge-response process, for example, the smart card requests an identifier from the end device and compares it with the identifier which is stored in the smart card.

[0013] From EP 1 552 484 A0 a computer is known which is associated with a Subscriber Identity Module (SIM) which is used in mobile phones operating in the GSM standard. A SIM module may be authenticated by the telephone network in the same way as SIM modules for a network telephone headset user, and may authenticate a PC user or the PC itself.

EP 1 909 431 A1 discloses a method which comprises connecting a host processor (HP2) to a controller via a combiner (C1) and transmitting secret data, i.e. an explicit code key, to the control unit, the data being written by the unit. controlling.

[0015] On the other hand, the invention is based on the task of providing an improved method of securing a smart card against unauthorized use. In addition, the invention is based on the task of creating an improved processor card and an improved processor card terminal.

[0016] The objects underlying the invention are solved thanks to the features of the independent patent claims. Advantageous embodiments are set out in the dependent claims.

[0017] According to the invention, a method of securing a smart card against unauthorized use has been provided. In addition to the processor card, this method also includes the processor card terminal itself.

[0018] By "chip card terminal" herein is meant any device that is designed to communicate with a smart card, for example, to route control signals to the smart card to the smart card and receive corresponding responses from the smart card. The communication between the smart card and the terminal for the smart cards can hereby take place in a contact, wireless, for example using RFID technique, or optionally via a contact or wireless, in particular via a so-called dual-mode interface. The processor card terminal may be a so-called 1st, 2nd or 3rd class processor card reader, with or without its own keyboard, or a computer to which the processor card reader is connected. The processor card terminal may also be a terminal provided for a specific purpose, such as a banking terminal for banking operations, a payment terminal, e.g. for purchasing electronic tickets, or an access terminal for unblocking access to a secure area.

[0019] By the term "smart card security" is meant here to protect the smart card in general or to protect one or more functions of the smart card. According to the invention, for example, a particularly valuable chip card function is secured, such as a signature function for generating an electronic signature, a payment function, an authentication function and the like.

According to one embodiment of the method according to the invention, the authenticated user of the smart card issuing site receives a secret identifier, generally referred to as a PIN code. In order to use a smart card, the identifier must first be entered on the terminal for smart cards, hereinafter referred to as the PIN code. Only when the 'PIN code is identical to the PIN code will it be possible to use a smart card or the protected function of a smart card.

To this end, the smart card terminal produces a cryptogram composed of at least one first communication parameter by means of a first symmetric key. The first symmetric key may be the PIN itself 'or a symmetric key derived from the PIN'. PIN 'serves, for example, as a so-called seed value for generating the first symmetric key by the smart card terminal.

[0022] The at least one communication parameter is such that a first communication channel which it secures may be defined between the terminal of the smart cards and the smart card. In order to be able to establish this secure first communication channel between the smart card and the chip card terminal, a cryptogram obtained with the first symmetric key is first transmitted over a predefined communication channel from the chip card terminal to the chip card. This predefined communication channel is thus defined as standard in order to establish initial communication between the smart card terminal and the smart card.

After transmitting the cryptogram over this predefined communication channel from the terminal of the smart cards to the smart card, the smart card attempts to decrypt the cryptogram with the second symmetric key. This decryption is only successful if the second symmetric key is the same as the first key, i.e. the condition PIN '= PIN is met.

Establishing a communication link over the secured first communication channel is therefore only possible if the condition PIN '= PIN is satisfied, because only in this case the smart card receives the message of the first communication parameter with which the secured first communication channel can be established.

[0025] The first communication parameter may be, for example, a forwarding frequency, a frequency hopping scheme, an encoding method and / or a modulation method.

[0026] On the other hand, when the condition PIN '= PIN is not satisfied, the first key derived from the PIN code' does not match the second key of the smart card. The result is that decrypting the cryptogram received by the smart card from the chip card terminal with the second key does not obtain the first communication parameter, but for example results in a second communication parameter that is different from the first communication parameter.

[0027] With the second communication parameter, a second communication channel can be defined which is different from the first communication channel. When the smart card receives a signal on the first communication channel, however, this is ignored because the smart card waits for a signal on the second communication channel. As a result, when the condition PIN '= PIN is not met, communication between the terminal for smart cards and the smart card does not take place.

[0028] According to one embodiment of the invention, the communication parameter may be an explicit key from an asymmetric key pair of the processor card terminal. In order to establish a symmetric key for communication between the processor card terminal and the smart card, e.g. according to the Diffie-Hellman method, the open key of the smart card terminal is encrypted with a first symmetric key obtained from the first identifier and sent over a predefined communication channel to the processor card. .

[0029] Only when the condition PIN '= PIN is met, the smart card receives the correct public key of the smart card terminal. According to the Diffie-Hellman method, the chip card terminal generates a third key from the explicit key of the chip card requested by e.g. the key server, while the chip card generates a third key from its private key and cryptogram decrypted with the second symmetric key, also in accordance with the Diffie-Hellman method, generates a fourth key, the fourth key being the same as the third key only if the condition PIN '= PIN is met.

[0030] The third and identical fourth symmetric key are used to decrypt the signals, in particular the control signals of the smart card, and respond to such smart card control signals that are exchanged between the processor card terminal and the smart card via the first communication channel. The first communication channel is at least additionally defined by a third key with which the first communication channel decrypts communication by means of a symmetric decryption method.

[0031] According to one embodiment of the invention, a discrete logarithmic cryptography (DLC) method is used to generate the third key by the smart card terminal and the fourth key by the smart card, the fourth key being the same as the third key when the condition is satisfied. PIN '= PIN.

[0032] In principle, any discrete logarithmic cryptography method described in, for example, National Institute of Standards and Technology (NIST), NIST Special Publication 800-56A, March, 2007, as well as in Standards is applicable to determine the third key. for Efficient Cryptography ”, Chapter 1: Elliptic Curve Cryptography, Certicom Research, September 20, 2000, Version 1.0. Such methods require the production of so-called domain parameters in order to generate an identical third and fourth key by the smart card terminal or by the smart card.

[0033] According to one embodiment of the invention, an Elliptic Curve Cryptography (ECC) method, in particular a Diffie-Hellman Elliptic Curve (ECDH), is used as the DLC.

[0034] According to an embodiment of the invention, a first identifier, i.e. the PIN ', which is input into the processor card terminal, is used as a so-called seed value for deriving the first symmetric key. This produces a key with a greater length than would be the case if the first code was used directly as the key.

[0035] According to one embodiment of the invention, a second identifier, i.e. a PIN, is stored on the smart card, from which a second key can be derived for decrypting the cryptogram initially received by the processor card terminal. The second identifier may be used as the seed value to derive the second key from the second identifier.

[0036] According to one embodiment of the invention, it is not the PIN which is stored on the smart card but only the second key. The second key is preferably stored in a non-volatile, secure memory area of ​​the processor card. Thus, unlike the prior art, it is not necessary to store the PIN code on the smart card as a reference value.

[0037] In accordance with one embodiment of the invention, the smart card has a mishandling counter. If, due to a wrong PIN entry, the first and second communication channels do not match with any message that the chip card receives on a communication channel other than the second or predefined channel, the chip card increases or decreases the malfunction counter. In other cases, messages that the smart card receives on a different communication channel than the second or predefined channel are ignored by the smart card. When the number of mishandling events exceeds a predetermined threshold value, the entire smart card or a specific function of the smart card is reversibly or irreversibly blocked.

[0038] According to one embodiment of the invention, the smart card has a first user function. The unused chip card is in a first use state where a specific communication parameter is determined for the first selection of the first communication channel. The processor card transitions from the first use state to the use state when it first receives a control signal from the processor card on this first communication channel. In order to use the smart card further, the smart card terminal must then select another communication parameter.

[0039] In a further aspect, the invention relates to a processor card with: an interface for communicating with a processor card terminal via a predefined communication channel and a plurality of further communication channels; with the decryption elements using the second symmetric key, a cryptogram, encrypted with the first symmetric key and received over a predefined channel; wherein the decryption results in at least one communication parameter when the first identifier previously entered into the processor card terminal is correct, wherein the communication parameter unambiguously establishes one of the further communication channels for secure communication between the processor card and the processor card terminal.

[0040] In a further aspect, the invention relates to a processor card terminal with means for inputting a first identifier, with means which, by means of a first symmetric key derived from the first identifier, produce a cryptogram from at least one first communication parameter. wherein by means of the communication parameter it is possible to define a secured first communication channel between the terminal of the smart cards and the smart card and means for transmitting the cryptogram to the smart card via the predefined communication channel.

[0041] In a further aspect, the invention relates to a method, wherein herein the discrete log cryptography method is an elliptic curve cryptography method.

[0042] In a further aspect, the invention relates to a method, wherein herein the discrete log cryptography method is an elliptic curve cryptography method based on the Diffie-Hellman protocol.

[0043] In a further aspect the invention relates to a method wherein the first identifier is used as seed value for deriving the first symmetric key by a smart card terminal.

[0044] In a further aspect, the invention relates to a method wherein a second identifier (140) is stored on the smart card from which a second key can be derived.

[0045] In a further aspect, the invention relates to a method wherein the second key is stored in a secure, non-volatile memory area of ​​the processor card.

[0046] In a further aspect the invention relates to a processor card terminal, the first communication parameter being a forwarding frequency, a frequency-hopping scheme, an encoding method and / or a modulation method.

[0047] Embodiments of the invention are explained in more detail below with reference to the drawings. Shown:

1 is a block diagram of a first embodiment of a processor card according to the invention and a processor card terminal,

FIG. 2 is a flowchart for one embodiment of the method according to the invention, FIG. 3 is a block diagram of a further embodiment of a smart card according to the invention and a terminal for smart cards, FIG.

FIG. 4 is a flowchart for a further embodiment of the method according to the invention. [0048] In the figures below, corresponding elements of the various embodiments are indicated with the same reference numerals.

[0049] FIG. 1 shows a block diagram of a smart card terminal 100. The processor card terminal 100 has an interface 102 for communicating with the processor card 104, which has a corresponding interface 106. Preferably, the interfaces 102 and 106 are made for wireless communication, for example by radio, in particular by RFID.

[0050] The interfaces 102 and 106 are, for example, such that different communication channels may be formed between the interfaces 102, 106, the communication channels differing from one another in the physical and / or logical planes. For example, you can create communication channels with different transmission rates. Communication channels can also be created based on various frequency - hopping schemes. By "frequency-hopping" herein is meant a frequency hopping method whereby the frequencies used for data transmission are continuously changed according to a predetermined scheme.

[0051] The interfaces 102 and 106 may also be made such that the different communication channels are formed by different coding methods and / or modulation methods such as frequency modulation, amplitude modulation, phase modulation, pulse width modulation or other modulation methods.

[0052] The various communication channels that may be established between the interfaces 102 and 106 will hereinafter be referred to as "the number of communication channels".

One of the communication channels 108 of the number of communication channels is predefined for initial communication between the smart card terminal 100 and the smart card 104. For example, the communication channel is predefined with respect to its forwarding frequency as well as the modulation and coding method used. .

[0054] The predefined communication channel is provided to convey, through the cryptogram 110, at least one communication parameter KI from the processor card terminal 100 to the processor card 104 to communicate to the processor card 104 which of the communication channels 112 from among the plurality of communication channels is to be used for. subsequent communication with the terminal of 100 smart cards.

[0055] The communication parameter KI also includes information that uniquely specifies this communication channel 112. This information may be in the form of a codeword. On the processor card 104, a so-called LUT can be stored in the non-volatile memory in which possible code words are assigned the specification of one of the communication channels out of a plurality of communication channels.

[0056] For selecting one of the communication channels from the plurality of communication channels, all possible communication channels may be available that may be established between the interfaces 102, 106, or some of them, then each communication channel out of the number of communication channels that may be indeed applicable for communication between the interfaces 102, 106, is assigned to a unique code word, which may be transferred as communication parameter 110 from the smart card terminal 100 to the smart card 104.

The smart card terminal 100 has a user interface 114 such as a keyboard or a graphical user interface through which the first code 116 can be entered. This first code will be referred to below as PIN 'without losing generality. The processor card terminal 100 has at least one processor 118 for executing an application program 120. Application program 120 may cause the generation of a control signal 122 to invoke a specific function 124 of the smart card 104. For example, application 120 needs a smart card function 124 to authenticate, generate an electronic signature, validate, specifically, access, perform a financial transaction. e.t.c.

[0059] The processor 118 is further operable to execute the program instructions of the communication module 126 that selects the communication channel 112 from the plurality of communication channels, and thereby selects the communication parameter 110. The selection of the communication parameter 110 may be according to a predetermined scheme or randomly. especially pseudo-randomly. For example, in the communication module 126, a list of various communication parameters 110 is stored and cyclically analyzed.

[0060] The processor 118 further serves to execute the program instruction 128 for encoding the symmetric communication parameter 110. The encoding is carried out with a PIN '. To this end, program instructions 128 may include a key generator 130.

[0061] The key generator 130 may be made such that it generates a first symmetric key from the PIN 'as seed value, which is hereinafter referred to as SI. The S1 key is used to symmetrically encode a communication parameter KI selected by the communication module 126. The communication parameter KI cryptogram resulting from symmetric encoding with the S1 key is transmitted over a predefined communication channel 108 from interface 102 to interface 106.

[0062] The processor card 104 has a processor 132 which is used to execute the program instructions of the communication module 134. The communication module 134 is performed to process a communication parameter KI possibly received at the terminal 100 of the processor cards. The communication module 134 may, for example, using the communication parameter KI as a key, refer to an assignment table, in particular a LUT, to retrieve parameters of the communication channel 112 selected by the chip card terminal 100, such as its transmission frequency and / or the methods used. coding and modulation.

[0063] The processor 132 further serves to execute program instruction 136 for symmetrically decoding the cryptogram 110 that the processor card 104 has received from the processor card terminal 100. For example, chip card 104 has a secure memory area 138 in which the second code 140 is stored. The second code, without losing generality, is referred to below as a PIN code. The PIN is separately communicated to the authorized user of the smart card with the handing over of the smart card 104, e.g. in the form of a so-called PIN code letter.

[0064] Program instructions 136 may include a key generator 142 that uses a PIN as a so-called seed value to derive a second key therefrom. This second symmetric key is hereinafter referred to as S2.

[0065] Alternatively, the key S2 may be stored in the secure memory area 138 of the smart card 104 instead of the PIN 140. The key generator 142, as well as the storage of the PIN 140 on the smart card 140, are then redundant. Thus, unlike the prior art, the smart card 140 does not necessarily have to store the PIN 140 as a reference value for validating the PIN '116.

[0066] The processor card 104 may further have an invalidation counter 144. The mishandling counter 144 is made such that each misuse of the smart card 104 is counted. The number of mishandling cases is compared with a predetermined threshold value. When this threshold value is reached, at least one smart card function 124 to which the malfunction counter 144 is assigned is reversibly or irreversibly blocked.

[0067] The chip card 104 may further include a first user function. The first use status of chip card 104 is defined, for example, by a particular communication parameter that specifies one of the number of communication channels to be used for the first use of the chip card.

[0068] To use a smart card 104, the procedure is as follows: The user enters the PIN '116 via the user interface 114 to the chip card terminal 100. This may occur upon a corresponding request from application program 120. Communication module 126 then selects the first possible communication parameter, for example from a predetermined list of communication parameters, thus the communication parameter KI.

[0069] The key generator 130 generates a key SI from the PIN '. The communication parameter KI is then encoded by executing program instruction 128 with a symmetric key SI. The resulting KI communication parameter cryptogram 110 is then transmitted over a predetermined communication channel 108 from interface 102 to interface 106 of processor card 104.

[0070] If desired, chip card 104 derives the key S2 from the PIN or looks up the key S2 directly in the secure memory area 138. With the key S2, an attempt is made to decrypt the cryptogram 110 of the communication parameter KI received at the processor card terminal 100 by executing the program instruction 136 by the processor card 104.

The result of this decryption attempt is a second communication parameter, hereinafter referred to as K2, and is forwarded to the communication module 134. This communication parameter K2 is identical to the communication parameter K1 only if the condition PIN '= PIN is satisfied, since then the SI key which was used for symmetric encoding may be the same as the S2 key which was used to symmetrically decrypt the cryptogram of the communication parameter KI.

[0072] With the communication parameter K2, a second communication channel 146 can be defined, namely by referring the communication module 134 to the assignment table using communication parameter K2. This second communication channel 146, in turn, is identical to the first communication channel 112 only if the condition PIN '= PIN is satisfied.

After transmitting the KI communication parameter cryptogram over the predefined communication channel 108, the processor card terminal 100 generates a smart card control signal 122 which is transmitted over the first communication channel 112 from interface 102 to interface 106. The processor card 104 or its communication channel 134 are set to receive on the second communication channel 146 based on communication parameter K2.

[0074] When the second communication channel 146 coincides with the first communication channel 112, the smart card control signal 122 is processed by the smart card 104 and the smart card function 124 is called. As a result, processor card 104 generates a response to the processor card control signal 122 and transmits this response over the first communication channel 112 back to the processor card 100.

[0075] Conversely, when the second communication channel 146 is not identical to the first communication channel 112, the chip card 104 ignores the chip card control signal received on the first communication channel 112 and increments the incorrect handling counter 144.

The communication channel 108 is defined, for example, by a forwarding frequency of 9 GHz, communications channel 112 by a forwarding frequency of 10 GHz, and communication channel 146 by a forwarding frequency of 11

GHz, with the transmission frequencies of the communication channels 112 and 146 deviating from each other because the PIN 'entered into the chip card terminal 100 is not the same as the PIN. When, in this case, processor card 104 receives a signal at 10 GHz from the processor card terminal 100, although it was expecting to receive at 11 GHz, that signal is ignored and the malfunction counter is incremented. As a result, the PIN code is checked by default, without the need to directly compare the PIN code with the PIN code, and without having to write the PIN code on the smart card.

[0077] Figure 2 shows the corresponding flowchart. In step 200, the PIN 'is entered into the smart card terminal. Then, in step 202, the processor card terminal 100 determines a communication parameter KI to select one of the communication channels from a plurality of communication channels. In step 204, the communication parameter KI is symmetrically encrypted with a PIN '. This can be done in such a way that a symmetric key SI is derived from the PIN code by means of a key generator, which then serves to encrypt the communication parameter 1.

[0078] In step 206, the KI communication parameter cryptogram produced with the SI key is transmitted over a predefined communication channel from the smart card terminal to the smart card.

[0079] The chip card 104 in step 208 attempts to decrypt the KI communication parameter based on the PIN. The correct PIN code can be written on the secured memory area of ​​the smart card and is used to output the symmetric key S2. Alternatively, the S2 key can also be written directly to the protected memory area of ​​the smart card.

[0080] Decoding the cryptogram of the communication parameter KI with the key S2 results in the communication parameter K2. Due to this communication parameter K2, it is possible to define a second communication channel among a number of these. Only when PIN 'is correct, i.e. when the condition PIN' = PIN is met, the communication parameters KI and K2 are identical.

[0081] In a first step 210, the smart card terminal generates a smart card control signal and sends it on the first communication channel specified by the KI communication parameter to the smart card (step 212). In step 214, the chip card can receive the control signal only if the second communication channel to which the chip card is set to receive is identical to the first communication channel, i.e. the condition PIN '= PIN is fulfilled. Otherwise, the smart card ignores the cryptogram received on the first communication channel and increases the invalid service counter.

[0082] In one embodiment of the invention, the communication parameter KI may be the public key of the smart card terminal. The cryptogram of this public key, which was generated with the key S1 by symmetric encryption, is transmitted by the smart card terminal to the smart card. The chip card receives the correct public key of the chip card terminal only when the condition PIN '= PIN is met, since only then is it possible to decrypt the cryptogram with the key S2 (compare the embodiment in Figure 1). The processor card terminal may retrieve the explicit key of the processor card, e.g. from an external key server via the network, in particular the Internet.

[0083] According to the Diffie-Hellman method, the processor card terminal can derive the symmetric key S3 from the private key of the processor card terminal and the explicit key of the processor card. Accordingly, the smart card can derive the symmetric key 4 from the explicit key of the smart card terminal and its private key also according to the Diffie-Hellman method. The S3 and S4 key are identical when the condition PIN '= PIN is met.

[0084] The first communication channel (cf. communication channel 112 of figure 1) is in this embodiment at least further defined by a symmetric key S3 = S4. The chip card control signal sent by the chip card terminal to the chip card is encrypted with the symmetric key S3 and the chip card can decrypt it, i.e. receive it, only if the chip card control signal can be decrypted with the key S4. Otherwise, the chip card control signal is ignored and the malfunction counter is incremented.

FIG. 3 shows an embodiment of the inventive smartcard and the inventive smartcard terminal, wherein a discrete logarithmic cryptography method is used to generate the key S3 or S4. In addition to the embodiment of Figure 1, processor 118 is used to execute program instructions 148 which use a so-called Key Establishment Scheme to generate the symmetric key S3.

[0086] The Key Establishment Scheme operates according to the method of Discrete Logarithmic Cryptography (DLC), in particular Elliptic Curve (EEC) cryptography, preferably according to the Diffie-Hellman Curve (ECDH) method. In order to generate the symmetric key S3, program instructions 148 first generate a first domain parameter, which is hereinafter called D1.

[0087] In addition, communication channel 126 may generate or read from the predetermined list a first channel KAI parameter that, for example, specifies the physical properties of the first communication channel. The first channel KI parameter corresponds to the channel KI parameter in the embodiment of Figure 1.

[0088] The domain parameter D1 and the channel KAI parameter or parameters are encrypted with an SI key by program instructions 128. The cryptogram 110 obtained with the key SI from KAI, D1 is transmitted over the predefined communication channel 108 from interface 102 to interface 106.

[0089] The smart card 104 decrypts the cryptogram 110 with the symmetric key S2. As a result of the decryption, the chip card 104 obtains a second channel parameter KA2 that corresponds to the communication parameter K2 in the embodiment of Figure 1. Further, the chip card receives the domain parameter D2. The channel KA2 parameter is processed by the communication module 134 to, for example, determine the physical specification of the second communication channel 146.

[0090] In addition to the embodiment of FIG. 1, chip card 104 has program instructions 150 that correspond in function to program instructions 148 and with which the chip card implements the Key Establishment Scheme.

[0091] The processor card terminal, by executing the program instruction 148 from the domain parameters D1, derives a symmetric key S3, stored in memory 152 of the processor card terminal 100. Accordingly, by executing the program instruction 150 by the processor card 104, a symmetric key S4 is derived from the domain parameters D2, which is stored in the memory 154 of the processor card 104.

[0092] The smart card control signal 122 is scrambled by the smart card terminal with the symmetric key S3 prior to transmission, and then transmitted over the first communication channel 112 specified by the channel KAI parameter. Smartcard 104 can receive the smartcard control signal 122 only when KA2 = KAI and D2 = Dl, which in turn is only possible when the condition PIN '= PIN is met.

[0093] An especially advantageous embodiment with this embodiment is that the third party is not able to track the transmission of the domain parameter D1 on the predetermined communication channel 108 because the transmission of the domain parameter D1 is in encrypted form.

[0094] Figure 4 shows a corresponding flowchart. In step 400, the user enters the PIN 'into the smart card terminal. From the PIN 'a symmetric key SI is derived.

[0095] In step 402, the Key Establishment Scheme begins. Then, in step 404, the domain D1 parameter set is produced. Using the domain parameter Dl, the smart card terminal generates a symmetric key S3. Moreover, in step 406, the processor card terminal generates the channel KAI parameter or reads it from the given list.

[0096] In step 408, the domain parameter D1 and / or the channel KAI parameter are encrypted with the S1 key. For example, the domain parameter Dl and the channel KAI parameter are related to each other, resulting in a single communication parameter which is then encrypted with the SI key. Alternatively, only the domain D1 parameters or only the channel KAI parameters or some of the domain parameters and / or channel parameters are encrypted with the SI key. The cryptogram resulting from the encryption with the SI key, as well as possibly the domain parameters and / or the channel parameters that have not been encrypted, in step 410 are transmitted to the smart card by the chip card terminal over a predefined channel (cf. communication channel 108 of figures 1 and 3) .

[0097] In step 412, the smart card attempts to decrypt the cryptogram with the key S2. The processor card 104 obtains the channel KA2 parameters and the domain D2 parameters based on this. From the domain D2 parameters, smart card 104 derives a key S4.

[0098] In step 414, the chip card terminal 100 generates a smart card control signal, which is encrypted with the key S3 (step 416), to be transmitted over the first communication channel defined by the channel KAI parameters (compare communication channel 112 in the embodiments of Figs. 1 and 3). The processor card terminal 100 transmits the smart card control signal at step 418.

[0099] Correct reception of this cryptogram by the smart card is only possible at step 420 if the second communication channel 146 agrees with the first communication channel 112, i.e. when KA2 = KAI, and otherwise it is possible to decode the control signal of the chip card using with the S4 key, i.e. when S4 = S3. The conditions KA2 = KAI and S4 = S3 can be met only when the user enters the correct PIN 'into the chip card terminal, i.e. when PIN' = PIN.

Lookup list

[0100]

100 processor card terminal

102 interface

104 processor card

106 interface

108 a predefined communication channel

110 communication parameter

112 first communication channel

114 User Interface

116 PIN '

118 processor

120 application program

122 smart card control signal

124 smart card function

126 communication module

128 program instructions

130 key generator

132 processor

134 communication module

136 program instructions

138 secured memory area

140 PIN

142 key generator

144 malfunction counter

146 second communication channel

148 program instructions

150 program instructions

152 memory

154 memory