Security of signed ELGamal encryption

  • Assuming a cryptographically strong cyclic group G of prime order q and a random hash function H, we show that ElGamal encryption with an added Schnorr signature is secure against the adaptive chosen ciphertext attack, in which an attacker can freely use a decryption oracle except for the target ciphertext. We also prove security against the novel one-more-decyption attack. Our security proofs are in a new model, corresponding to a combination of two previously introduced models, the Random Oracle model and the Generic model. The security extends to the distributed threshold version of the scheme. Moreover, we propose a very practical scheme for private information retrieval that is based on blind decryption of ElGamal ciphertexts.

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Author:Claus Peter SchnorrGND, Markus Jakobsson
Place of publication:Berlin [u.a.]
Document Type:Preprint
Date of Publication (online):2005/07/12
Year of first Publication:2000
Publishing Institution:Universit├Ątsbibliothek Johann Christian Senckenberg
Release Date:2005/07/12
Page Number:16
First Page:73
Last Page:89
Preprint, sp├Ąter in: Advances in cryptology, 2000, Lecture notes in computer science, Vol. 1976, S. 73-89
Source:Lecture notes in computer science, Vol. 1976
Institutes:Informatik und Mathematik / Mathematik
Informatik und Mathematik / Informatik
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 51 Mathematik / 510 Mathematik
Licence (German):License LogoDeutsches Urheberrecht