Conditional Proxy Broadcast Re-Encryption

• Main Authors: CHU, Cheng-Kang, Weng, Jian, Chow, Sherman S. W., Zhou, Jianying, DENG, Robert H.
• Format: text
• Language: English
• Published: Institutional Knowledge at Singapore Management University 2009
• Subjects: broadcast encryption; conditional proxy re-encryption; hierarchical identity-coupling broadcast encryption; proxy re-encryption; Information Security
• Online Access: https://ink.library.smu.edu.sg/sis_research/288; https://ink.library.smu.edu.sg/context/sis_research/article/1287/viewcontent/Chu2009_Chapter_ConditionalProxyBroadcastRe_En.pdf
• Institution: Singapore Management University

A proxy re-encryption (PRE) scheme supports the delegation of decryption rights via a proxy, who makes the ciphertexts decryptable by the delegatee. PRE is useful in various applications such as encrypted email forwarding. In this paper, we introduce a more generalized notion of conditional proxy broadcast re-encryption (CPBRE). A CPBRE scheme allows Alice to generate a re-encryption key for some condition specified during the encryption, such that the re-encryption power of the proxy is restricted to that condition only. This enables a more fine-grained delegation of decryption right. Moreover, Alice can delegate decryption rights to a set of users at a time. That is, Alice's ciphertexts can be re-broadcasted. This saves a lot of computation and communication cost. We propose a basic CPBRE scheme secure against chosen-plaintext attacks, and its extension which is secure against replayable chosen-ciphertext attacks (RCCA). Both schemes are unidirectional and proved secure in the standard model. Finally, we show that it is easy to get a unidirectional RCCA-secure identity-based proxy re-encryption from our RCCA-secure CPBRE construction.