| 摘要 |
<p>The present invention relates to the generation of an encryption key for a message to be transmitted over a communications network, where there is no real time link between the encryption and decryption devices. Without limitation, one application of the present invention is in financial transactions between a customer, vendor and financial institution. In essence, the present invention stems from the recognition that if the transactions are not necessarily to occur in real time nor in an environment of total security in transmission, then the transaction must be considered as unidirectional from the customer (or their device) to the issuer. Thus, from the customers end, a unique key is generated for each transaction, preferably without reference to external devices. In one form, the unique key protects in particular, a PIN or the like provided by the cardholder. However, the device issuing institution will be aware of the basic encryption key for each device, and when coupled with further data (in the illustrative case a random number input to a rotation or other rearrangement algorithm), the issuer can recover the correct key and decrypt this protected part of the transaction identification block. Also two unidirectional transactions may form a bidirectional transaction session.</p> |
