The efficiency of a black-box reduction is an important goal of modern cryptography. Traditionally, the time complexity and the success probability were considered as the main aspects of efficiency measurements. In CRYPTO 2017, Auerbach et al. introduced the notion of memory-tightness in cryptographic reductions and showed a memory-tight reduction of the existential unforgeability of the RSA-FDH signature scheme. Unfortunately, their techniques do not extend directly to the reductions involving intricate RO-programming. The problem seems to be inherent as all the other existing results on memory-tightness are lower bounds and impossibility results. In fact, Auerbach et al. conjectured that a memory-tight reduction for security of Hashed-ElGamal KEM is impossible. We refute the above conjecture. Using a simple RO simulation technique, we provide memory-tight reductions of security of the Cramer-Shoup and the ECIES version of Hashed-ElGamal KEM.We prove memory-tight reductions for different variants of Fujisaki-Okamoto Transformation. We analyze the modular transformations introduced by Hofheinz, Hövermanns and Kiltz (TCC 2017). In addition to the constructions involving implicit rejection, we present a memory-tight reduction for the security of the transformation. Our techniques can withstand correctness-errors, and applicable to several lattice-based KEM candidates.
|Title of host publication||Public-Key Cryptography – PKC 2020 - 23rd IACR International Conference on Practice and Theory of Public-Key Cryptography, Proceedings|
|Editors||Aggelos Kiayias, Markulf Kohlweiss, Petros Wallden, Vassilis Zikas|
|Number of pages||30|
|Publication status||Published - 2020|
|Event||23rd IACR International Conference on the Practice and Theory of Public-Key Cryptography, PKC 2020 - Edinburgh, United Kingdom|
Duration: 4 May 2020 → 7 May 2020
|Name||Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)|
|Conference||23rd IACR International Conference on the Practice and Theory of Public-Key Cryptography, PKC 2020|
|Period||4/05/20 → 7/05/20|
Bibliographical noteFunding Information:
We thank Eike Kiltz for encouraging us to write up and submit the work. We are thankful to the reviewers for their comments on this and the previous versions of the paper. The author is supported by SERB ECR/2017/001974.
© 2020, International Association for Cryptologic Research.
- FO transformation
- Memory-tight reduction
ASJC Scopus subject areas
- Theoretical Computer Science
- Computer Science(all)