[Resource Topic] 2006/071: A Fast and Key-Efficient Reduction of Chosen- Ciphertext to Known-Plaintext Security

Welcome to the resource topic for 2006/071

Title:
A Fast and Key-Efficient Reduction of Chosen- Ciphertext to Known-Plaintext Security

Authors: Ueli Maurer, Johan Sjödin

Abstract:

Motivated by the quest for reducing assumptions in security proofs in
cryptography, this paper is concerned with designing efficient
symmetric encryption and authentication schemes based on any weak pseudorandom function (PRF) which can be much more efficiently
implemented than PRFs. Damgard and Nielsen (CRYPTO '02) have
shown how to construct an efficient symmetric encryption scheme based
on any weak PRF that is provably secure against chosen-plaintext
attacks. The main ingredient is a range-extension construction for
weak PRFs. By using well-known techniques, they also showed how their
scheme can be made secure against the stronger chosen-ciphertext attacks.

The results of our paper are three-fold. First, we give a range-extension construction for weak PRFs that is optimal within a
large and natural class of reductions (especially all known today).
Second, we propose a construction of a regular PRF from any weak PRF.
Third, these two results imply a (for long messages) much more
efficient chosen-ciphertext secure encryption scheme than the one
proposed by Damgard and Nielsen. The results also give answers to
open questions posed by Naor and Reingold (CRYPTO '98) and by
Damgard and Nielsen.

ePrint: https://eprint.iacr.org/2006/071

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