CPC H04W 12/069 (2021.01) [H04M 3/42034 (2013.01); H04W 12/041 (2021.01); H04M 3/493 (2013.01)] | 14 Claims |
1. An authentication server comprising:
a number receiver that receives a number of a user terminal from a callee who has received a call originated from the user terminal;
an device authenticator that determines whether to generate an authentication key based on the number of the user terminal received from the callee and a caller number received from the user terminal, and generates the authentication key when it is determined to generate the authentication key; and
an authentication key transmitter that transmits the authentication key to the user terminal.
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