| 摘要 |
A load on a server or a network is suppressed at a minimum, the authentication server is not necessary, and download of falsified software is prevented. A server creates a time-limited authentication key, computes a hash value of a file included in update software for each file to create a hash table in which hash values of a file are listed, and encrypts the hash table using the authentication key. A unit obtains the encrypted hash table and the authentication key from a server. An information terminal obtains the encrypted hash table from the unit, obtains the authentication key from the unit, determines whether or not a time limit of the authentication key is valid, obtains the encrypted hash table from the server if the time limit is determined to be valid as a result of the determination, decrypts the tables using the authentication key, compares the tables after decryption, and initiates download of the update software if both the tables are identical to each other. |
