Patent ID: 8085938

Claim:
A secret information management system for managing a secret information of a user, comprising: a data division unit configured to divide the secret information into a plurality of divided data by using a secret sharing scheme, such that the secret information cannot be recovered from any one of the divided data alone but the secret information can be recovered from a prescribed number of the divided data; a divided data storing unit configured to store a part of the plurality of divided data into a terminal of the user as user's divided data, and a rest of the plurality of divided data into one or more of deposit servers; a data re-division unit configured to generate a plurality of re-divided data different from the plurality of divided data obtained by the data division unit, from a combination of the prescribed number of the divided data among the divided data stored in the deposit servers by using the secret sharing scheme; and a re-divided data storing unit configured to store a part of the plurality of re-divided data into the terminal as newly generated user's divided data and a rest of the plurality of re-divided data into the deposit servers as newly generated divided data; wherein the data division unit and the data re-division unit use the secret sharing scheme which is a data division method for dividing the secret information into the divided data in a desired number of divisions according to a desired processing unit bit length in which the divided data in the desired number of divisions are generated by generating a plurality of original partial data by partitioning the secret information in units of the processing unit bit length, generating a plurality of random number partial data of the processing unit bit length from a random number in a length shorter than or equal to a bit length of the secret information, in correspondence to respective ones of the plurality of original partial data, and generating each divided partial data in the processing unit bit length that constitutes each divided data by calculating exclusive OR of the original partial data and the random number partial data, and the re-divided data in the desired number of division are generated by generating a plurality of new random number partial data of the processing unit bit length from a newly generated random number, and generating the re-divided partial data in the processing unit bit length by calculating exclusive OR of the divided partial data and the new random number partial data.