| 摘要 |
<p>A communications terminal 1 is equipped with a separate, removable encryption module 3 in the form of a smart card that is inserted into the standard SIM socket 2 of the communications terminal 1. Sealed copies of encryption keys that have been delivered to the communications terminal 1 are stored in an internal memory 4 of the communications terminal 1. When a new traffic encryption key is required by the encryption module 3, the encryption module 3 first looks to retrieve that key from the memory 4 of the communications terminal 1. If a key is not available in the terminal, it is requested via the communications network, e.g. using over the air rekeying (OTAR). This procedure reduces signalling activity. The keys are sent encrypted with a sealing key, a copy of which is located on the smart card.</p> |
