Encryption and processing of signals from smart card - using value determined by traversal of tree determined by repeated processing of original data, as key

摘要

The encryption is generated on the card by calculating a value from repeated application of coding functions to a value generated by the card. A succession of intermediate values are produced that are stored as a tree structure. The calculated value forms the root of a sub-tree. The calculated value is then transmitted to the card reader. The card reader requests transmission of selected intermediate values of the tree to allow it to obtain the root value through an authentification path. A different value for the sub-tree root is calculated for each message, the value serving as a key. ADVANTAGE - Cryptography procedure that requires little memory and so can be implemented on smart cards at reasonable cost.