| 摘要 |
PROBLEM TO BE SOLVED: To prevent reduction in the utilization factor of a wireless circuit, as well as improving confidentiality with respect to a malicious third party, when distributing a modified software to a potable telephone. SOLUTION: Encrypting modified software 3 is previously fetched in each portable telephone 5 in off-line manner, and only a key information 4, necessary for decoding, is distributed to the telephone in on-line manner via a wireless circuit from a radio base station 7. In this way, increase in the load on the wireless circuit and the decrease in the utilization factor of the circuit are reduced, and the confidentiality of information is markedly improved, because the encrypting modified software 3 and the decoding key information 4 are distributed by using separate methods. COPYRIGHT: (C)2004,JPO
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