Cryptology ePrint Archive: Report 2014/849

A Proxy Re-Encryption Scheme with the Unforgeability of Re-Encryption Keys against Collusion Attacks

Ryotaro Hayashi and Tatsuyuki Matsushita

Abstract: Proxy re-encryption (PRE) schemes are cryptosystems which allow a proxy who has a re-encryption key to convert a ciphertext originally encrypted for one party into a ciphertext which can be decrypted by another party. In IWSEC 2011, Hayashi et al. proposed the new security notion for PRE called ``unforgeability of re-encryption keys against collusion attacks,'' UFReKey-CA for short. They proposed the PRE schemes and claimed that their schemes meet UFReKey-CA. However, Isshiki et al. pointed out that the schemes do not meet UFReKey-CA in IWSEC 2013. It is an open problem of constructing the scheme which meets UFReKey-CA. In this paper, we propose new PRE schemes which meet confidentiality (RCCA security) assuming that the q-wDBDHI problem is hard and meet UFReKey-CA assuming that the 2-DHI problem is hard.

Category / Keywords: public-key cryptography / proxy re-encryption, non-transferability, unforgeability of re-encryption keys against collusion attacks, UFReKey-CA

Date: received 17 Oct 2014

Contact author: ryotaro hayashi at toshiba co jp

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Version: 20141022:141317 (All versions of this report)

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