As a related system for pseudonymization, there is a method presented in Non-Patent Document 1.  Hereinafter, the method of Non-Patent Document 1 will be described by referring to FIG.  3. 
An anonymous system 100 for pseudonymization includes an encryption function 102 of a common key encryption system and a key 101 required for the encryption function 102.  Further, the anonymous system 100 inputs information of a name 104 from a clinical system 103 as an element of the encryption function 102. 
According to an operation of an authorized person, the anonymous system 100 inputs the information of the name 104 to the encryption function 102 and inputs information of the key 101 as an element of the encryption function, executes an arithmetic operation by the encryption function 102, and outputs information of a pseudonym 105 to a research system 106.     Non-Patent Document 1: Alain Lemay, Jean-MarcLinal, “Pseudonymization of Radiology Data for Research Purposes”, Journal of Digital Imaging, Volume 20, Number 3/September, 2007, pp.  284-295