Authentication system, authentication method, and authentication program

An authentication method of an authentication system that is connected to an information processing apparatus via a first network, is connected to a certificate issuing server that issues a certificate including a valid period and permitting connection to a second network, and determines propriety of connection to the second network,

• the authentication method comprising:
• holding a certificate with which connection has been permitted in a past;
• and
• determining propriety of connection to the second network by verifying a certificate transmitted from the information processing apparatus, wherein
• the determining propriety of connection includes:
• verifying a valid period of a certificate transmitted from the information processing apparatus;
• permitting connection to the second network when the certificate is valid;
• determining, when the certificate is not valid, whether an identical certificate is held;
• and
• permitting connection to the second network based on a determination result.

A non-transitory recording medium storing a computer readable authentication program of an authentication system that is connected to an information processing apparatus via a first network, is connected to a certificate issuing server that issues a certificate including a valid period and permitting connection to a second network, and determines propriety of connection to the second network, wherein

• a computer of the authentication system executes the authentication program to execute processing comprising:
• holding a certificate with which connection has been permitted in a past;
• and
• determining propriety of connection to the second network by verifying a certificate transmitted from the information processing apparatus, and
• the determining propriety of connection includes:
• verifying a valid period of a certificate transmitted from the information processing apparatus;
• permitting connection to the second network when the certificate is valid;
• determining, when the certificate is not valid, whether an identical certificate is held;
• and
• permitting connection to the second network based on a determination result.