A STRATEGY FOR SECURING APDU TRANSMISSION

Abstract

The smart card is being used all over the world, because of its power to store data securely and execute calculations confidentially. This paper proposes an easy way to implement the strategy which can guarantee data integrity and privacy in the transmission path between the terminal application of the smart card and the smart card. This strategy consists of cryptographic functions of message and methods for transmitting APDU and managing secret keys. Some cryptographic functions of message are defined and developed for transmitting APDU confidentially. These cryptographic functions can keep the byte length of input and output messages identical. This strategy for transmitting APDU points out how to call cryptographic functions to encode or decode the data body of APDU, and how to construct a modified APDU message structure according to the original APDU message structure, which will be sent to its intended recipient instead of the original APDU message structure. With the proper secret keys, the authorized party can recover this modified APDU to its corresponding original APDU properly, without any information leakage. The transfer of secret keys to other parties is the most difficult aspect of secure APDU transmission, whereas data encryption/decryption is relatively straightforward. Two distinct strategies for managing secret keys, namely the static and the dynamic are introduced and compared. The dynamic strategy is preferred for a terminal application and smart card which do not need to authenticate each other. The implementation of this dynamic strategy has been detailed.