| 摘要 |
The method includes preparing a portable data processing device ("smart card") at each site having a first data record which can only be read at that site but which can be written to at any site, and a second data record which can only be written at that site but which can be read at any site, the device also containing a testable key particular to that device. Each site also creates and publishes a set of test patterns against which the authenticity of the card can be verified. Each site then creates one part of the key to be agreed upon, and a test pattern for that key part. The test pattern is written to the site's own smart card in the second data record. The cards are exchanged, and the received cards are tested for authenticity using the published test patterns. Once accepted as genuine, the test pattern for the key part of the other site is read and stored. The key part previously generated is written onto the first data record of the received card. The cards are exchanged again. The key part is read at the home site of the card. The key part is verified for authenticity against the stored test pattern which was received earlier. Each site then combines the received key part with the locally created key part and they now share a common key. |
