Cryptology ePrint Archive: Report 2007/171

Chosen-Ciphertext Secure Proxy Re-Encryption

Ran Canetti and Susan Hohenberger

Abstract: In a proxy re-encryption (PRE) scheme, a proxy is given special information that allows it to translate a ciphertext under one key into a ciphertext of the same message under a different key. The proxy cannot, however, learn anything about the messages encrypted under either key. PRE schemes have many practical applications, including distributed storage, email, and DRM. Previously proposed re-encryption schemes achieved only semantic security; in contrast, applications often require security against chosen ciphertext attacks. We propose a definition of security against chosen ciphertext attacks for PRE schemes, and present a scheme that satisfies the definition. Our construction is efficient and based only on the Decisional Bilinear Diffie-Hellman assumption in the standard model. We also formally capture CCA security for PRE schemes via both a game-based definition and simulation-based definitions that guarantee universally composable security. We note that, simultaneously with our work, Green and Ateniese proposed a CCA-secure PRE, discussed herein.

Category / Keywords: public-key cryptography / re-encryption, chosen-ciphertext security, obfuscation

Publication Info: Full version of paper in ACM CCS 2007.

Date: received 8 May 2007, last revised 29 Oct 2007

Contact author: susan at cs jhu edu

Available format(s): PDF | BibTeX Citation

Version: 20071029:223232 (All versions of this report)

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