According to an aspect of the embodiment, a packet analyzing apparatus monitors a concentration level of input and output access from an access apparatus to a disk device, specifies a data area to which the concentration level of input and output access exceeds a first threshold, and instructs a storage server to cache the data area. The air pressure applied is varied by the device according to the invention so that at least three different pressure values can be adjusted. A product of an encryption of the log-probability of the state for the current element, an encryption of a transition probability to the state, and the encryption of a log-probability of the current element of the observation sequence is determined iteratively, for each state of the HMM, to produce an encrypted matrix of indexes of the states; and the encrypted matrix is transmitted to the client. The SOI diodes of the present invention improve the protection level offered for electrical overstress electrostatic discharge due to the low power density and heating for providing more junction area than normal ones. The detecting unit detects either the first type medium or the second type medium used.