Abstract: A method of authenticating a password and a portable device thereof are provided. The method includes: displaying an input keyboard on which a plurality of objects are arranged; changing an object arranged on the input keyboard according to a manipulation of a user; and if an object pattern arranged in a designated position of the input keyboard corresponds to a preset password pattern, authenticating the user. Therefore, it is difficult to use artifacts on the display screen to trace a password after entry, and thus security is improved. As a result, a protection of personal information of a user is strengthened.

Abstract: The method of decrypting a ciphertext includes: pre-storing a plurality of polynomial functions into which a secret key decrypting a ciphertext to a plaintext according to a public-key cryptography algorithm is broken down; receiving the ciphertext generated based on the secret key which is broken down into the plurality of polynomial functions from a ciphertext generating device; and decrypting the received ciphertext into the plaintext based on the pre-stored polynomial functions.

Abstract: The method of decrypting a ciphertext includes: pre-storing a plurality of polynomial functions into which a secret key decrypting a ciphertext to a plaintext according to a public-key cryptography algorithm is broken down; receiving the ciphertext generated based on the secret key which is broken down into the plurality of polynomial functions from a ciphertext generating device; and decrypting the received ciphertext into the plaintext based on the pre-stored polynomial functions.

Abstract: A portable device for diagnosing a diagnosis device, a method for providing a diagnosis service, and a diagnosis system thereof are provided. The portable device includes a setting information collecting unit which collects setting information relating to the diagnosis device which is output from the diagnosis device, a diagnosis device information generating unit which generates diagnosis device information based on the setting information, a communication unit which transmits the diagnosis device information to a server, and a diagnosis result output unit which, if diagnosis result information is received from the server via the communication unit, outputs the received diagnosis result information. Accordingly, an electronic apparatus without a network function may provide a diagnosis service remotely by using a portable device.