International Association for Cryptologic Research

International Association
for Cryptologic Research


Navid Ghaedi Bardeh


New Key-Recovery Attack on Reduced-Round AES
Navid Ghaedi Bardeh Vincent Rijmen
A new fundamental 4-round property of AES, called the zero-difference property, was introduced by Rønjom, Bardeh and Helleseth at Asiacrypt 2017. Our work characterizes it in a simple way by exploiting the notion of related differences which was introduced and well analyzed by the AES designers. We extend the 4-round property by considering some further properties of related differences over the AES linear layer, generalizing the zero-difference property. This results in a new key-recovery attack on 7-round AES which is the first attack on 7-round AES by exploiting the zero-difference property.
The Exchange Attack: How to Distinguish Six Rounds of AES with $2^{88.2}$Chosen Plaintexts
Navid Ghaedi Bardeh Sondre Rønjom
In this paper we present exchange-equivalence attacks which is a new cryptanalytic attack technique suitable for SPN-like block cipher designs. Our new technique results in the first secret-key chosen plaintext distinguisher for 6-round AES. The complexity of the distinguisher is about $$2^{88.2}$$ in terms of data, memory and computational complexity. The distinguishing attack for AES reduced to six rounds is a straight-forward extension of an exchange attack for 5-round AES that requires $$2^{30}$$ in terms of chosen plaintexts and computation. This is also a new record for AES reduced to five rounds. The main result of this paper is that AES up to at least six rounds is biased when restricted to exchange-invariant sets of plaintexts.