User authentication method with enhanced security

A user authentication method, the method comprising:

• generating, by a user terminal, a first common authentication key by combining a private password with a mechanical unique key of the user terminal and encrypting the combined information if a user of the user terminal enters the private password for user registration using the user terminal and providing, by the user terminal, the generated first common authentication key to an authentication server, and registering, by the authentication server, the first common authentication key and user information by matching the first common authentication key with the user information;
• generating, by the authentication server, a server authentication key by combining an embedded unique key of a certificate authority with the first common authentication key and encrypting the combined information and generating, by the authentication server, server authentication information by calculating a first one time password (OTP) using a first operation key generated by combining the server authentication key a gap time value in which a time taken for the user to enter the private password is measured every 1/n seconds, wherein n is a positive real number, and a gap time key which is a numeral value extracted by criteria from the gap time value;
• measuring, by the user terminal, the gap time value if the user enters the private password for authentication and transmitting, by the user terminal, the measured gap time value to the authentication server, generating, by the user terminal, a second common authentication key in real time by combining the private password with the mechanical unique key of the user terminal and encrypting the combined information, generating, by the user terminal, a user authentication key by combining the unique key of the certificate authority previously provided from the authentication server with the second common authentication key and encrypting the combined information, and generating, by the user terminal, user authentication information by calculating a second OTP using a second operation key generated by combining the user authentication key with the gap time value or the gap time key;
• and
• performing, by the authentication server, user authentication when the server authentication information is identical to the user authentication information.