**Are you an EPFL student looking for a semester project?**

Work with us on data science and visualisation projects, and deploy your project as an app on top of GraphSearch.

Publication# Resistance Against Iterated Attacks by Decorrelation Revisited

Abstract

Iterated attacks are comprised of iterating adversaries who can make $d$ plaintext queries, in each iteration to compute a bit, and are trying to distinguish between a random cipher $C$ and the ideal random cipher $C^*$ based on all bits. In EUROCRYPT '99, Vaudenay showed that a $2d$-decorrelated cipher resists to iterated attacks of order $d$ when iterations make almost no common queries. Then, he first asked what the necessary conditions are for a cipher to resist a non-adaptive iterated attack of order $d$. Secondly, he speculated that repeating a plaintext query in different iterations does not provide any advantage to a non-adaptive distinguisher. We close here these two long-standing open problems. We show that, in order to resist non-adaptive iterated attacks of order $d$, decorrelation of order $2d-1$ is not sufficient. We do this by providing a counterexample consisting of a cipher decorrelated to the order $2d-1$ and a successful non-adaptive iterated attack of order $d$ against it. Moreover, we prove that the aforementioned claim is wrong by showing that a higher probability of having a common query between different iterations can translate to a high advantage of the adversary in distinguishing $C$ from $C^*$. We provide a counterintuitive example consisting of a cipher decorrelated to the order $2d$ which can be broken by an iterated attack of order 1 having a high probability of common queries.

Official source

This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.

Related concepts

Loading

Related publications

Loading

Related publications (1)

Related concepts (13)

Cipher

In cryptography, a cipher (or cypher) is an algorithm for performing encryption or decryption—a series of well-defined steps that can be followed as a procedure. An alternative, less common ter

Random oracle

In cryptography, a random oracle is an oracle (a theoretical black box) that responds to every unique query with a (truly) random response chosen uniformly from its output domain. If a query is repe

Iteration

Iteration is the repetition of a process in order to generate a (possibly unbounded) sequence of outcomes. Each repetition of the process is a single iteration, and the outcome of each iteration is th

Loading

Asli Bay, Atefeh Mashatan, Serge Vaudenay

Iterated attacks are comprised of iterating adversaries who can make d plaintext queries, in each iteration to compute a bit, and are trying to distinguish between a random cipher C and the perfect cipher C* based on all bits. Vaudenay showed that a 2d-decorrelated cipher resists to iterated attacks of order d. when iterations have almost no common queries. Then, he first asked what the necessary conditions are for a cipher to resist a non-adaptive iterated attack of order d. I.e., whether decorrelation of order 2d-1 could be sufficient. Secondly, he speculated that repeating a plaintext query in different iterations does not provide any advantage to a non-adaptive distinguisher. We close here these two long-standing open problems negatively. For those questions, we provide two counter-intuitive examples. We also deal with adaptive iterated adversaries who can make both plaintext and ciphertext queries in which the future queries are dependent on the past queries. We show that decorrelation of order 2d protects against these attacks of order d. We also study the generalization of these distinguishers for iterations making non-binary outcomes. Finally, we measure the resistance against two well-known statistical distinguishers, namely, differential-linear and boomerang distinguishers and show that 4-decorrelation degree protects against these attacks.

2014