Article and method for transaction irregularity detection
Articles and methods for transaction irregularity detection are disclosed. In one example, the article discloses: a memory including a record of a last-reported security-device transaction with the security-device, and including a last-reported transaction counter value associated with the last-reported security-device transaction; a previous device identifier; a record of the previous security-device transaction with the security-device, and including the previous device identifier associated with the previous security-device transaction; a record of a current security-device transaction with the security-device, and including a currently-reported transaction counter value associated with the current security-device transaction; and a back-end device tagging the previous device with fraud if the current transaction counter value differs from the last-reported transaction counter value by other than an increment. In one example, the method discloses: a transaction irregularity detection process based on the article.
1. A method for detecting a fraudulent transaction within a plurality of transactions between a smart card and a plurality of terminals, the method comprising:
for each transaction between the smart card and a respective terminal:
the smart card receiving a unique identifier (UID) of the respective terminal from the respective terminal, wherein the respective terminal is configured with a secure access module that prevents the respective terminal from modifying the UID of the respective terminal;
the smart card encrypting the UID of the respective terminal using a transaction key;
the smart card transmitting the encrypted UID of the respective terminal to the respective terminal, wherein the respective terminal does not know the transaction key;
the smart card incrementing a transaction counter value;
the smart card transmitting the transaction counter value to the respective terminal;
the respective terminal transmitting the encrypted UID and the transaction counter value to a fraud detecting device;
for a currently-reported transaction between the smart card and a particular terminal:
the fraud detecting device receiving a claim from the particular terminal, wherein the claim comprises an encrypted UID of the particular terminal and a counter value associated with the currently-reported transaction;
the fraud detecting device storing the counter value of the currently-reported transaction as a currently-reported counter value, wherein the counter value from a last-reported transaction is stored in the fraud detecting device as a last-reported counter value;
the fraud detecting device storing the encrypted UID of the particular terminal of the currently-reported transaction as a currently-reported terminal UID, wherein the encrypted UID of the particular terminal associated with the last-reported transaction is stored in the fraud detecting device as a last-reported terminal UID;
the fraud detecting device comparing the currently-reported counter value with the last-reported counter value;
the fraud detecting device determining whether the currently-reported counter value differs from the last-reported counter value by an expected increment amount;
in response to detecting, by the fraud detecting device, that the currently-reported counter value differs from the last-reported counter value by any value other than the expected increment amount, identifying the last-reported transaction as a fraudulent transaction and retrieving the last-reported terminal UID of the particular terminal associated with the last-reported transaction as an identification of a perpetrator of the fraudulent transaction.
2. The method of claim 1 , further comprising:
the fraud detecting device decrypting the last-reported terminal UID received from the smart card with a stored transaction key.
3. The method of claim 2 , wherein the stored transaction key is an asymmetric message authentication code (MAC) key.
4. The method of claim 2 , wherein the stored transaction key cannot be accessed by any terminals of the plurality of terminals.
5. The method of claim 2 , wherein the stored transaction key is a symmetric transaction message authentication code (MAC) key.
6. The method of claim 2 , wherein
the stored transaction key is equal to the transaction key used by the smart card to encrypt the UID of the respective terminal.
7. The method of claim 1 , wherein the last-reported transaction is a value transaction.
8. The method of claim 1 , wherein the expected increment amount between the currently-reported counter value and the last-reported counter value is one.
9. The method of claim 1 , wherein
the transaction key used by the smart card to encrypt the UID of the respective terminal is a session key derived from a Transaction Message Authentication Code (MAC) key.
10. The method of claim 1 , further comprising:
for each transaction between the smart card and the respective terminal:
the smart card calculating a Transaction Message Authentication Code (MAC) Value based on the transaction counter value and the transaction key;
the smart card transmitting the Transaction MAC Value (TMV) to the respective terminal;
the respective terminal transmitting the TMV to the fraud detecting device.
11. The method of claim 10 , further comprising:
for the currently-reported transaction between the smart card and the particular terminal:
the fraud detecting device receiving a TMV associated with the currently-reported transaction in the claim;
the fraud detecting device authenticating execution of the currently-reported transaction between the smart card and the particular terminal based upon the TMV included in the claim, wherein the TMV is authenticated based on the currently-reported counter value included in the claim and a stored transaction key in the fraud detecting device.
12. The method of claim 11 , wherein
the stored transaction key used by the fraud detecting device for authentication is a session key derived from a Transaction Message Authentication Code (MAC) key.