An authentication device comprising: transmission means for transmitting a challenge to a terminal device on which the challenge is presented to a user to be authenticated, the challenge being information serving as a basis on which the user inputs information to be used in an authentication process; and determination means for performing the authentication process to determine whether a response is correct or wrong, the response being information which is inputted by the user to the terminal device based on the challenge, wherein the transmission means includes a function to transmit, to the terminal device, a plurality of challenges to the user to be authenticated, the challenges being different from one another, and at least one of the challenges is information requesting the user to make the response that includes biometric information on the user; and wherein the determination means further includes a function to determine whether time information regarding the challenge and the response to the challenge satisfies a condition regarding the response, the determination means performs identity verification using the biometric information on the user included in the response to the challenge, the identity verification is a processing that verifies whether the user to be authenticated is a preregistered user, and the determination means verifies existence of the user based on the determination result whether the response is correct or wrong and whether the time information related to the challenge satisfies the condition regarding the response, and the user is authenticated when the user is a preregistered user and existence of the user is verified, characterised in that the time information includes an input duration for the response which defines a time period when the user is inputting the response to the challenge. transmission means for transmitting a challenge to a terminal device on which the challenge is presented to a user to be authenticated, the challenge being information serving as a basis on which the user inputs information to be used in an authentication process; and determination means for performing the authentication process to determine whether a response is correct or wrong, the response being information which is inputted by the user to the terminal device based on the challenge, wherein the transmission means includes a function to transmit, to the terminal device, a plurality of challenges to the user to be authenticated, the challenges being different from one another, and at least one of the challenges is information requesting the user to make the response that includes biometric information on the user; and wherein the determination means further includes a function to determine whether time information regarding the challenge and the response to the challenge satisfies a condition regarding the response, the determination means performs identity verification using the biometric information on the user included in the response to the challenge, the identity verification is a processing that verifies whether the user to be authenticated is a preregistered user, and the determination means verifies existence of the user based on the determination result whether the response is correct or wrong and whether the time information related to the challenge satisfies the condition regarding the response, and the user is authenticated when the user is a preregistered user and existence of the user is verified, characterised in that the time information includes an input duration for the response which defines a time period when the user is inputting the response to the challenge.