The present invention relates to a method for increasing the security with respect to the authentication key sent. According to the present invention, (a) the server and in a state in which the authentication key is shared with each other between the terminal device and the server transfers the filter for performing the authentication and operation to the terminal device, the instructions cause the terminal device the comprising: using the authentication key and the filter supports allows the support through a predetermined calculation to produce a modified authentication key, to the terminal device to generate a security authentication key, to encrypt the modified authentication key, the generated; and (b) wherein the server, the server retains the phase, and use the authentication key and the filter in through the predetermined operation, and generating a modified authentication key, encrypts the generated modified authentication key for generating a security authentication key; And (c) if the security authentication key is sent to the server from the terminal apparatus, the server, a step of authentication by comparing the security authentication and security authentication key received from the terminal device and the server has the method for increased security is provided in relation to the authentication key sent to. According to the invention, it is effective to transmit only a portion of the authentication key to increase the security by preventing the entire authentication key is leaked.