Security of Cloud-Based Revocable Identity-Based Proxy Re-Encryption Scheme

Seunghwan PARK  Dong Hoon LEE  

IEICE TRANSACTIONS on Information and Systems   Vol.E99-D   No.7   pp.1933-1936
Publication Date: 2016/07/01
Online ISSN: 1745-1361
DOI: 10.1587/transinf.2016EDL8042
Type of Manuscript: LETTER
Category: Information Network
revocable identity-based encryption,  key revocation,  cloud-based identity-based proxy re-encryption,  ciphertext update,  

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Designing secure revocable storage systems for a large number of users in a cloud-based environment is important. Cloud storage systems should allow its users to dynamically join and leave the storage service. Further, the rights of the users to access the data should be changed accordingly. Recently, Liang et al. proposed a cloud-based revocable identity-based proxy re-encryption (CR-IB-PRE) scheme that supports user revocation and delegation of decryption rights. Moreover, to reduce the size of the key update token, they employed a public key broadcast encryption system as a building block. In this paper, we show that the CR-IB-PRE scheme with the reduced key update token size is not secure against collusion attacks.