| 摘要 |
PROBLEM TO BE SOLVED: To provide a portable telephone system capable of preventing software from being rewritten excepting a rolling-back and a regular update version. SOLUTION: A main body program stores a newly distributed encryption key in an encryption key storage region 125 of a main body nonvolatile built-in memory 12. When the distribution of a new main body program 131 for updating and new version data 132 is detected, the main body program delivers control to a rewriting program and the rewriting program decodes the new version data 132 with the new encryption key and decodes former version data with a former encryption key. If a new country code in the new version data 132 matches a former country code in the former version data, and new version information in the new version data 132 is later than former version information in the former version data, the rewriting program rewrites the main body program with the new main body program 131. COPYRIGHT: (C)2007,JPO&INPIT |
