Information processing system, information processing apparatus, information processing method, and recording medium

An information processing apparatus comprising:

• a memory storing instructions;
• and
• one or more processors configured to execute the instructions to:
• generate a tag relating to transmission data by using a common key;
• generate a chain that is a sequence of values generated in order by repeatedly applying a one-way function to a value and in which generation order of each value is inversely associated with transmission order of data;
• generate authentication information for the transmission data by combining a value associated in the chain with transmission order of the transmission data with a tag relating to the transmission data;
• and
• transmit the transmission data and authentication information for the transmission data to another information processing apparatus that applies the one-way function to a value in the chain extracted by using a tag relating to received data and authentication information for the received data, the tag relating to the received data being generated by using the common key, and verifies whether a value associated in the chain with transmission order of data received in the past is generated or not.

An information processing method comprising:

• in a first information processing apparatus,
• generating a tag relating to transmission data by using a common key,
• generating a chain that is a sequence of values generated in order by repeatedly applying a one-way function to a value and in which generation order of each value is inversely associated with transmission order of data,
• generating authentication information for the transmission data by combining a value associated in the chain with transmission order of the transmission data with a tag relating to the transmission data, and
• transmitting the transmission data and the authentication information for the transmission data to a second information processing apparatus;
• and
• in the second information processing apparatus,
• receiving data and authentication information for the data from the first information processing apparatus,
• generating a tag relating to the received data by using the common key,
• extracting a value in the chain from the authentication information for the received data by using the tag relating to the received data, and
• authenticating the received data by applying the one-way function to a value in the chain extracted from the authentication information for the received data and verifying whether a value associated in the chain with transmission order of data received in the past is generated or not.