Enciphering apparatus and method, deciphering apparatus and method as well as information processing apparatus and method

An information processing method for an information processing system composed of a plurality information processing apparatus connected to each other by a bus, said information processing apparatus including first information processing apparatus each having a function whose change is not open to a user, and second information processing apparatus each having a function whose change is open to a user, the steps performed by each of said first information processing apparatus comprising:

• receiving enciphered data;
• generating a first information;
• generating a second information;
• producing a cryptographic key using the first information generated in the first generating step and the second information generated in the second generating step;
• and
• deciphering said received enciphered data using said cryptographic key, wherein said cryptographic key is changed at a predetermined timing while the data is being deciphered in accordance with a change in said second information;
• and
• the steps performed by each of said second information processing apparatus comprising:
• receiving enciphered data;
• generating the first information;
• generating the second information;
• producing a first cryptographic key using one of the first information and the second information;
• producing a second cryptographic key using the other of the first information and the second information. wherein said cryptographic key is changed at a predetermined timing while the data is being deciphered in accordance with a change in said second information;
• and
• deciphering the received enciphered data using the first cryptographic key;
• and
• deciphering the deciphered data further using the second cryptographic key.

An information processing system, comprising:

• a plurality information processing apparatus connected to each other by a bus;
• said plurality of information processing apparatus including a group of first information processing apparatus each having a function whose change is not open to a user, and a group of second information processing apparatus each having a function whose change is open to a user;
• each of said first information processing apparatus including:
• a first receiver;
• a first decipherer coupled with said receiver;
• a first information generator coupled with said decipherer;
• a second information generator coupled with said decipherer;
• and
• a first cryptographic key producer coupled with said decipherer, whereby said first decipherer deciphers data received by said first receiver using a first cryptographic key produced by said first cryptographic key producer in accordance with a first information generated by said first information generator and a second information generated by said second information generator, said second information being changed at a predetermined time while the data is being deciphered;
• each of said second information processing apparatus including:
• a first receiver;
• a first decipherer coupled with said first receiver;
• a second decipherer coupled with said first decipherer;
• a first information generator coupled with said first receiver;
• a second information generator coupled with said first receiver;
• a first cryptographic key producer coupled with said first and second information generators;
• and
• a second cryptographic key producer coupled with said first and second information generators, whereby said first decipherer deciphers data received by said first receiver using a first cryptographic key produced by said first cryptographic key producer in accordance with one of a first information generated by said first information generator and a second information generated by said second information generator, and said second decipherer further deciphers data previously deciphered by said first decipherer using a second cryptographic key produced by said second cryptographic key producer in accordance with the other of said first information and said second information, said second information being changed at a predetermined time while data is being deciphered.

An information processing apparatus for deciphering data, comprising:

• a receiver;
• a cryptographic key producer composed of a software program coupled with said receiver;
• a first decipherer coupled with said cryptographic key producer and said receiver;
• and
• a second decipherer coupled with said cryptographic key producer and said first decipherer;
• whereby said first decipherer deciphers enciphered data received by said receiver in accordance with one of a first cryptographic key produced by said cryptographic key producer or a second cryptographic key produced by said cryptographic key producer, and said second decipherer deciphers and processes data previously deciphered by said first decipherer in accordance with the other of said first and second cryptographic keys, said second cryptographic key being changed at a predetermined time during deciphering by said information processing apparatus.