Patent ID: 8612742

Claim:
A software update system of an information terminal comprising: an information terminal; a software download server connected to the information terminal via a network, the software download server storing update software; and a security unit communicable with the information terminal via a near field radio network, wherein the software download server creates a time-limited authentication key, computes a hash value of a file included in the update software for each file to create a hash table in which hash values of a file is listed, and encrypts the hash table using the authentication key, the security unit obtains the encrypted hash table and the authentication key from the software download server, and the information terminal obtains the encrypted hash table from the security unit as a first table, obtains the authentication key from the security unit, determines whether or not a time limit of the authentication key is valid, obtains the encrypted hash table from the software download server as a second table if the time limit is determined to be valid, decrypts the first and second tables using the authentication key, compares the first and second tables after decryption, initiates download of the update software from the software download server if it is determined both the tables are identical to each other, computes a hash value of the downloaded update software as the download is completed, compares the computed hash value with the hash value in either the first or second table after the decryption, and permits activation of the downloaded update software if both hash values are identical to each other.