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Fair Encryption of RSA Keys

  • Guillaume Poupard
  • Jacques Stern
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1807)

Abstract

Cryptography is more and more concerned with elaborate protocols involving many participants. In some cases, it is crucial to be sure that players behave fairly especially when they use public key encryption. Accordingly, mechanisms are needed to check the correctness of encrypted data, without compromising secrecy. We consider an optimistic scenario in which users have pairs of public and private keys and give an encryption of their secret key with the public key of a third party. In this setting we wish to provide a publicly verifiable proof that the third party is able to recover the secret key if needed. Our emphasis is on size; we believe that the proof should be of the same length as the original key.

In this paper, we propose such proofs of fair encryption for El Gamal and RSA keys, using the Paillier cryptosystem. Our proofs are really efficient since in practical terms they are only a few hundred bytes long. As an application, we design a very simple and efficient key recovery system.

Keywords

Discrete Logarithm Security Parameter Choose Ciphertext Attack Random Tape Cheat Strategy 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • Guillaume Poupard
    • 1
  • Jacques Stern
    • 1
  1. 1.Département d’informatiqueÉcole Normale SupérieureParis Cedex 05France

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