| 摘要 |
<p>A long message (ie too long to be transmitted as a single SDS/SMS) is stored in buffer 23. The initial portion of the message is transferred to secure buffer 25, which typically holds a single SDS/SMS worth of data. A partial cryptographic check-sum (PCCS) is taken of this data 26 and combined with a pseudo-random number 27 to form a cryptographic message header which is output to buffer 32 and used as an initialisation vector (IV) for stream encryption 28. The whole message is then stream encrypted 28 using the IV from 27 and secret key from 30 and the result stored in buffer 32. The secure module 24 also generates a full cryptographic check sequence (FCCS) 29 of the message and appends it in buffer 32. The encrypted message, header and FCCS in buffer 32 is then fragmented into SDS/SMS size segments and inserted into the payload of individual messages for transmission. The receiver concatenated the message payloads to reassemble the encrypted message, which is then decrypted.</p> |
