CryptoDB
Yi Chen
Publications
Year
Venue
Title
2023
ASIACRYPT
Differential-Linear Approximation Semi-Unconstrained Searching and Partition Tree: Application to LEA and Speck
Abstract
The differential-linear attack is one of
the most effective attacks against ARX ciphers.
However, two technical problems are preventing it from
being more effective and having more applications:
(1) there is no efficient method to search for
good differential-linear approximations.
Existing methods either have many constraints or are currently inefficient.
(2) partitioning technique has great potential
to reduce the time complexity of the key-recovery attack,
but there is no general tool to construct partitions for ARX ciphers.
In this work, we step forward in solving the two problems.
First, we propose a novel idea for generating new
good differential-linear approximations from known ones,
based on which new searching algorithms are designed.
Second, we propose a general tool named partition tree,
for constructing partitions for ARX ciphers.
Based on these new techniques,
we present better attacks for two ISO/IEC standards,
i.e., LEA and Speck.
For LEA, we present the first 17-round distinguisher which
is 1 round longer than the previous best distinguisher.
Furthermore, we present the first key recovery attacks on
17-round LEA-128, 18-round LEA-192, and 18-round LEA-256,
which attack 3, 4, and 3 rounds more than the previous best attacks.
For Speck, we find better differential-linear distinguishers for Speck48 and Speck64.
The first differential-linear distinguishers for Speck96 and Speck128 are also presented.
Coauthors
- Zhenzhen Bao (1)
- Hongbo Yu (1)