A Closer Look at Anonymous Proxy Re-Encryption Schemes
Anonymity is one of the most desired properties of a Proxy Re-encryption scheme. Any user communicating over the public channel, availing cloud for proxy re-encryption services requires that any entity (an attacker or cloud administrator) must not infer either the contents of the ciphertexts (confidentiality) or the identities of the participants (anonymity). It is clear that a proxy re-encryption scheme must be collusion-resistant to satisfy the anonymity notion. There are no CCA-secure collusion-resistant proxy re-encryption schemes in the literature which satisfy the anonymity property. In ASIA CCS ’14, an anonymous proxy re-encryption scheme was presented  and we present a weakness in the CCA-security proof of their scheme. We present the first proxy re-encryption scheme which is anonymous, collusion-resistant and prove its CCA-security in the random oracle model. We also design a simple, efficient, collusion-resistant CCA-secure proxy re-encryption scheme which is interesting in its own right. In fact, our anonymous scheme is an extension of our novel collusion-resistant scheme.
KeywordsProxy re-encryption Anonymity Collusion resistance Random oracle model CCA Security
This work is supported by Ministry of Electronics & Information Technology, Government of India under Project No. CCE/CEP/22/VK& CP/CSE/14-15 on ISEA-phase II.
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