RE-ENCRYPTION METHOD, RE-ENCRYPTION SYSTEM, AND RE-ENCRYPTION DEVICE

摘要

PROBLEM TO BE SOLVED: To securely avoid encryption data's browsing by unauthorized persons including a device manager, in an environment in which browsing right management for each user is performed by holding, in a predetermined device, encryption data shared by a plurality of users.SOLUTION: A re-encryption system 1 has a configuration including: a re-encryption device 20 that receives, from a user terminal of a data creator, first encryption data obtained by encrypting a plaintext by using a first encryption key of the data creator and second and third encryption data obtained by encrypting the first encryption key and predetermined data generated from the first encryption key by using a predetermined algorithm, respectively by using a commutative encryption algorithm, and individually re-encrypts the second and third encryption data so as to be capable of being decrypted by using a decryption key of a user having a browsing right; and a user terminal 10 that acquires the first encryption data and the respective re-encrypted second and third encryption data from the re-encryption device 20, decrypts the re-encrypted second encryption data by using the user's decryption key to obtain the first encryption key, and uses the first encryption key to decrypt the first encryption data and output the plaintext.SELECTED DRAWING: Figure 1