Method for detecting and reacting against possible attack to security enforcing operation performed by a cryptographic token or card
The approach defines a protection mechanism against attacks to a security enforcing operation performed by cryptographic token or smart card. It is based on an attack detector which signals the main elaboration or processing system regarding a potential attack situation. The approach addresses SIM cloning problems of telecommunications operators who use old and breakable cryptographic algorithms such as the COMP-128 and do not want to invest in updating the network authentication systems with more resistant authentication cryptographic algorithms. The approach may be applicable to the typical telecommunications operator in an emerging market that does not use state of the art technology.
1. A method for protecting a cryptographic token against a security attack, the method comprising:
assigning a respective ponder value to each of a plurality of different types of input commands, the respective ponder values being variably weighted according to relevant security of the different input commands;
detecting input commands input to the cryptographic token;
updating a counter value based upon the respective ponder values assigned to the detected different types of input commands, the counter value thereby being increased and decreased depending on a sequence of the detected different types of input commands;
comparing the counter value with a reference threshold; and
providing a warning signal output indicating a security attack based upon the comparison.
2. A method according to claim 1 , wherein the cryptographic token includes a microcontroller, and the warning signal output is provided to the microcontroller.
3. A method according to claim 1 , wherein the counter value is initialized with a predetermined starting value based upon operation of the cryptographic token.
4. A method according to claim 1 , wherein the cryptographic token includes a microcontroller; and wherein the input commands input to the cryptographic token are detected before they are processed by the microcontroller.
5. A method according to claim 1 , wherein the counter value is constantly compared with the threshold value.
6. A method according to claim 1 , wherein the counter value is one of a positive and a negative value.
7. A method according to claim 1 , wherein the reference threshold is one of an end counter value and a reset counter value.
8. A cryptographic token comprising:
a security attack detector comprising
a ponder over block configured to assign respective ponder values to each of a plurality of different types of input commands for the token, the respective ponder values being variably weighted according to relevant security of the different input commands,
a counter coupled to an output of said ponder over block configured to store a counter value, the counter value being updated based upon the respective ponder values assigned to the detected different types of input commands, the counter value thereby being increased and decreased depending on a sequence of the detected different types of input commands,
a threshold reference block defining a comparison value, and
a comparator configured to compare the counter value with the threshold value and provide an output warning signal indicating a security attack.
9. A cryptographic token according to claim 8 , wherein the output warning signal delays subsequent cryptographic token operations.
10. A cryptographic token according to claim 8 , wherein said counter comprises an associated non-volatile memory to store the counter value.
11. A cryptographic token according to claim 8 , wherein the counter value is initialized with a predetermined starting value based upon operation of the cryptographic token.
12. A cryptographic token according to claim 8 , wherein said ponder over block comprises a look up table.
13. A cryptographic token according to claim 12 , wherein the ponder values of the look up table are updated after the processing of an input command.
14. A cryptographic token including a microcontroller, the token comprising:
a security attack detector comprising
a ponder over block configured to assign respective ponder values to each of a plurality of different types of input commands for the token, the respective ponder values being variably weighted according to relevant security of the different input commands,
a counter coupled to an output of said ponder over block configured to store a counter value, the counter value being updated based upon the respective ponder values assigned to the detected different types of input commands, the counter value thereby being increased and decreased depending on a sequence of the detected different types of input commands,
a threshold reference block defining a comparison value, and
a comparator configured to compare the counter value with the threshold value and provide an output warning signal to the microcontroller based thereon and indicating a security attack.
15. A cryptographic token according to claim 14 , wherein the output warning signal is applied to the microcontroller to delay subsequent cryptographic token operations.
16. A cryptographic token according to claim 14 , wherein said counter comprises an associated non-volatile memory portion of said microcontroller to store the counter value.