Abstract: A target sends ID of a key table. The apparatus receives the ID. The apparatus sends ID of an authentication table to the target. The apparatus sends a challenge corresponding to a pair of the ID of the key table and the ID of the authentication table, to the target. The target obtains, from the key table, a key corresponding to a pair of the ID of the key table and the ID of the authentication table. The target generates a response from the challenge and the key. The target sends the response to the apparatus. The apparatus obtains, from the authentication table, a response corresponding to a pair of the ID of the key table and the ID of the authentication table. The apparatus authenticates the target based on the responses.

Abstract: A processing unit processes an input signal from an external apparatus and includes a first terminal to which a reference voltage is input from the external apparatus, a second terminal to which a first pulse signal having a first frequency is input from the external apparatus, and a control portion to process the input signal. A memory stores data to be transmitted to the external apparatus, and a clock generating unit generates a clock signal having a higher frequency than the first frequency of the first pulse signal. To transmit a data signal to the external apparatus from the processing unit, the control portion switches a load between the first terminal and the second terminal based on the data stored in the memory during a period in which a second pulse signal having a second frequency lower than the first frequency is input from the external apparatus.

Abstract: An authentication method includes: at a first device, selecting an original key in which a first identifier has a first value and a second identifier has a second value from m original keys and generating an authentication key based on the selected original key and the authentication identifier; at a second device, selecting an authentication key generated from the original key in which the first identifier has the first value and the second identifier has the second value from n authentication keys, generating response data based on challenge data and the authentication key, and notifying the generated response data to the first device; at the first device, generating verification data based on the challenge data and the authentication key, and authenticating the authentication target device by comparing the verification data with the response data.

Abstract: An authentication method includes: at a first device, selecting an original key in which a first identifier has a first value and a second identifier has a second value from m original keys and generating an authentication key based on the selected original key and the authentication identifier; at a second device, selecting an authentication key generated from the original key in which the first identifier has the first value and the second identifier has the second value from n authentication keys, generating response data based on challenge data and the authentication key, and notifying the generated response data to the first device; at the first device, generating verification data based on the challenge data and the authentication key, and authenticating the authentication target device by comparing the verification data with the response data.

Abstract: A data carrier apparatus includes a duty detector configured to determine a duty ratio of each pulse of a pulse signal that is received, a frequency detector configured to determine a period of each pulse of the pulse signal, and a demodulator configured to determine a value of data being carried by the pulse signal based on a determination result of the duty detector unit and a determination result of the frequency detector.

Abstract: A processing unit processes an input signal from an external apparatus and includes a first terminal to which a reference voltage is input from the external apparatus, a second terminal to which a first pulse signal having a first frequency is input from the external apparatus, and a control portion to process the input signal. A memory stores data to be transmitted to the external apparatus, and a clock generating unit generates a clock signal having a higher frequency than the first frequency of the first pulse signal. To transmit a data signal to the external apparatus from the processing unit, the control portion switches a load between the first terminal and the second terminal based on the data stored in the memory during a period in which a second pulse signal having a second frequency lower than the first frequency is input from the external apparatus.

Abstract: A communication apparatus includes a first terminal that receives a reference voltage, a second terminal that receives a pulse signal, and at least one processor to execute instructions. The instructions are executed to generate a clock signal that has a frequency higher than a frequency of the received pulse signal, count a number of pulses of the clock signal and determine a count value counted during a first cycle that is a cycle of the pulse signal to the second terminal, and, during a period of data transmission, increase or decrease an electric current that flows between the communication apparatus and the external apparatus according to a data value of data to be transmitted to the external apparatus. Data is transmitted to the external apparatus at least once during the first cycle, and data switch timing during the first cycle is based on the count value.

Abstract: A target sends ID of a key table. The apparatus receives the ID. The apparatus sends ID of an authentication table to the target. The apparatus sends a challenge corresponding to a pair of the ID of the key table and the ID of the authentication table, to the target. The target obtains, from the key table, a key corresponding to a pair of the ID of the key table and the ID of the authentication table. The target generates a response from the challenge and the key. The target sends the response to the apparatus. The apparatus obtains, from the authentication table, a response corresponding to a pair of the ID of the key table and the ID of the authentication table. The apparatus authenticates the target based on the responses.

Abstract: A data carrier apparatus includes: a first determination unit configured to determine a duty ratio of each pulse of a pulse signal that is received; a second determination unit configured to determine a period of each pulse of the pulse signal; and a third determination unit configured to determine a value of data being carried by the pulse signal based on a determination result of the first determination unit and a determination result of the second determination unit.

Abstract: A communication apparatus includes: a terminal to which a pulse signal is input from an external apparatus; an acquiring unit configured to acquire a count value during a first cycle that is a cycle of the pulse signal; and a transmitting unit configured to, during a period of data transmission, increase or decrease an electric current that flows between the communication apparatus and the external apparatus according to a data value of data to be transmitted. The transmitting unit is further configured to perform switching on the data to be transmitted at least once during the first cycle, and determine a data switch timing during the first cycle based on the count value.