International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

John P. Steinberger

Publications

Year
Venue
Title
2018
EUROCRYPT
2018
CRYPTO
Provable Security of (Tweakable) Block Ciphers Based on Substitution-Permutation Networks 📺
Substitution-Permutation Networks (SPNs) refer to a family of constructions which build a wn-bit block cipher from n-bit public permutations (often called S-boxes), which alternate keyless and “local” substitution steps utilizing such S-boxes, with keyed and “global” permutation steps which are non-cryptographic. Many widely deployed block ciphers are constructed based on the SPNs, but there are essentially no provable-security results about SPNs.In this work, we initiate a comprehensive study of the provable security of SPNs as (possibly tweakable) wn-bit block ciphers, when the underlying n-bit permutation is modeled as a public random permutation. When the permutation step is linear (which is the case for most existing designs), we show that 3 SPN rounds are necessary and sufficient for security. On the other hand, even 1-round SPNs can be secure when non-linearity is allowed. Moreover, 2-round non-linear SPNs can achieve “beyond-birthday” (up to $$2^{2n/3}$$ 22n/3 adversarial queries) security, and, as the number of non-linear rounds increases, our bounds are meaningful for the number of queries approaching $$2^n$$ 2n. Finally, our non-linear SPNs can be made tweakable by incorporating the tweak into the permutation layer, and provide good multi-user security.As an application, our construction can turn two public n-bit permutations (or fixed-key block ciphers) into a tweakable block cipher working on wn-bit inputs, 6n-bit key and an n-bit tweak (for any $$w\ge 2$$ w≥2); the tweakable block cipher provides security up to $$2^{2n/3}$$ 22n/3 adversarial queries in the random permutation model, while only requiring w calls to each permutation, and 3w field multiplications for each wn-bit input.
2017
CRYPTO
2017
JOFC
2016
EUROCRYPT
2016
EUROCRYPT
2016
CRYPTO
2015
FSE
2015
TCC
2014
CRYPTO
2014
CRYPTO
2014
EUROCRYPT
2013
CRYPTO
2012
EUROCRYPT
2012
CRYPTO
2012
CRYPTO
2011
CRYPTO
2011
EUROCRYPT
2011
ASIACRYPT
2010
EUROCRYPT
2010
EUROCRYPT
2009
CRYPTO
2008
EUROCRYPT
2008
CRYPTO
2007
EUROCRYPT

Program Committees

FSE 2018
Eurocrypt 2017
Eurocrypt 2016
Crypto 2013
Eurocrypt 2013