2. A pseudonymization device which decrypts an encrypted name part and converts the decrypted name part into a pseudonym wherein the encrypted name part is a name part that is dispersed by a unit of dispersion with which a user cannot be specified by the dispersed name parts of the user, disclosure information regarding the dispersed name parts and the dispersed name parts are correlated by correlation information, and the dispersed name parts and the correlation information are encrypted, the pseudonymization device further comprising: a decryption module which receives an encrypted text and refers to the correlation information of the encrypted text by using encryption information allotted to an own device to decrypt the dispersed and encrypted name part allotted to the own device, and also decrypts the encrypted disclosure information by using the allotted encryption information; an inverse number calculation module which includes a pseudonymization key for converting the dispersed and encrypted name part into the pseudonym, performs a multi-party calculation by conducting a communication mutually with another pseudonymization device, disperses an inverse number of a sum of the encrypted name parts and the pseudonymization key so as not to overlap with the pseudonym generated by another pseudonymization device to calculate a dispersion value of the inverse number, and generates it as information of the pseudonym, by using the pseudonymization key; and an encrypted text generation module which generates an encrypted text containing the pseudonym generated by the inverse number multi-party calculation module, the correlation information, and the disclosure information, and discloses the encrypted text on a communications net as an encrypted text.
3. The pseudonymization device as claimed in claim 2 , wherein the inverse number calculation module generates a commitment regarding the converted pseudonym and disclosure information for disclosing the converted pseudonym.