| 摘要 |
<P>PROBLEM TO BE SOLVED: To make it possible to protect confidentiality of content information in comparison with a configuration controlling browsing of a content by using only a term of validity. <P>SOLUTION: A server 10A and a smart phone 50A share a plurality of random numbers to which order is assigned and utilize the random number having an ordinal number of (i) as a cryptographic key. The smart phone 50A retains encrypted customer information and an encrypted common key X(i) generated by encrypting a common key Kd used for decryption with the (i)-th random number. The server 10A calculates a decryption key d(i) corresponding to the (i)-th random number and transmits the key to the smart phone 50A. The smart phone 50A calculates the common key Kd by decryption processing using the decryption key d(i); re-encrypts the common key Kd with the (i+1)-th random number to retain it as the encrypted common key X(i+1) and deletes the (i+1)-th random number, after validity of the decryption key d(i) expires or at the time of the end of browsing. <P>COPYRIGHT: (C)2012,JPO&INPIT |
