Cryptology ePrint Archive: Report 2002/042

A Unified Methodology For Constructing Public-Key Encryption Schemes Secure Against Adaptive Chosen-Ciphertext Attack

Edith Elkind and Amit Sahai

Abstract: We introduce a new methodology for achieving security against adaptive chosen-ciphertext attack (CCA) for public-key encryption schemes, which we call the {\em oblivious decryptors model}. The oblivious decryptors model generalizes both the two-key model of Naor and Yung, as well the Cramer--Shoup encryption schemes. The key ingredient in our new paradigm is Sahai's notion of Simulation-Sound NIZK proofs.

Our methodology is easy to use: First, construct an encryption scheme which satisfies the ``bare'' oblivious-decryptors model: This can be done quite easily, with simple proofs of security. Then, by adding a Simulation-Sound NIZK proof, the scheme becomes provably CCA-secure. Note that this paradigm allows for the use of {\em efficient} special-purpose Simulation-Sound NIZK proofs, such as those recently put forward by Cramer and Shoup. We also show how to present all known efficient (provably secure) CCA-secure public-key encryption schemes as special cases of our model.

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

Date: received 4 Apr 2002, last revised 5 Apr 2002

Contact author: elkind at cs princeton edu

Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | BibTeX Citation

Note: Fixed some typos.

Version: 20020405:204459 (All versions of this report)

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