Title: CIPHERTEXT DIVERGE-MERGE SCHEME OF IDENTITY-BASED ENCRYPTION FOR CLOUD-BASED FILE TRANSMISSION SERVICE

Issue Number: Vol. 5, No. 1
Year of Publication: 2015
Page Numbers: 52-59
Authors: Makoto Sato, Masami Mohri, Hiroshi Doi, Yoshiaki Shiraishi
Journal Name: International Journal of Digital Information and Wireless Communications (IJDIWC)
- Hong Kong
DOI:  http://dx.doi.org/10.17781/P001618

Abstract:


Cloud-based file transmission services have attracted attention as the way of sending files. However, not a few people have a reluctance to put their serious information on cloud servers. Encrypting and decrypting files on user’s terminals should resolve this concern. To avoid oppressing computational power of clients’ terminals, these ones should be as light as possible. In identity-based encryption (IBE), an identity (ID) such as mobile phone numbers is used as public keys, so there is no need for public key certificates. However, IBE has the key escrow problem that the private key generator (PKG) could see any message because all private keys used in decryption are generated by it. In this paper, we show how to configure cloud-based file transmission service that uses IBE and is free from the problem. In order to show that only receivers can decrypt ciphertexts, we define two attack models that either the PKG and the service providing server or the e-mail server constituting the proposed scheme collude with an adversary, and prove that our scheme is secure against passive attack in the models. Then, we compare the amount of computation of private key extraction, encryption and decryption.