Key Update Mechanism for Network Storage of Encrypted Data

Cryptography is now popularized and is widely used anywhere for many aims such as data confidentiality and integrity. The key of cryptography has a lifetime, thus a key update issue is well-known to be one of hard problems in practice. According to the National Institute of Standards and Technology SP 800-57, the lifetime of the cryptographic key and the lifetime of encrypted data are strictly limited. In other words, the encrypted data is required to be periodically re-encrypted. In this paper, we point out that this key update issue is now crucial in network storage and propose a key update mechanism efficiently reducing the communication and computation cost of re-encryption.