scholarly journals New Approach towards Generalizing Feistel Networks and Its Provable Security

2021 ◽  
Vol 2021 ◽  
pp. 1-26
Author(s):  
Jiajie Liu ◽  
Bing Sun ◽  
Chao Li
Keyword(s):  
Provable Security ◽  
Block Ciphers ◽  
New Approach ◽  
Feistel Networks ◽  
Beyond Birthday Bound ◽  
Feistel Structure ◽  
Coefficient Technique

This paper proposes a new approach to generalizing Feistel networks, which unifies the classical (balanced) Feistel network and the Lai–Massey structure. We call the new structure extended Feistel (E-Feistel) network. To justify its soundness, we investigate its indistinguishability using Patarin’s H-coefficient technique. As a result, it is proved that the 4-round key-alternating E-Feistel (KAEF) cipher with adequately derived keys and identical round functions is secure up to 2 n / 2 queries, i.e., birthday-bound security. In addition, when adjacent round keys are independent and independent round functions are used, the 6-round KAEF is secure up to beyond-birthday-bound 2 2 n / 3 queries. Our results indicate that the E-Feistel structure is secure and reliable and can be adopted in designing practical block ciphers.

scholarly journals Provably Quantum-Secure Tweakable Block Ciphers

2021 ◽  
pp. 337-377
Author(s):  
Akinori Hosoyamada ◽  
Tetsu Iwata
Keyword(s):  
Polynomial Time ◽  
Provable Security ◽  
Block Cipher ◽  
Block Ciphers ◽  
Quantum Superposition ◽  
Quantum Cryptanalysis ◽  
Classical Setting ◽  
Time Quantum ◽  
Symmetric Key ◽  
Arbitrary Quantum

Recent results on quantum cryptanalysis show that some symmetric key schemes can be broken in polynomial time even if they are proven to be secure in the classical setting. Liskov, Rivest, and Wagner showed that secure tweakable block ciphers can be constructed from secure block ciphers in the classical setting. However, Kaplan et al. showed that their scheme can be broken by polynomial time quantum superposition attacks, even if underlying block ciphers are quantum-secure. Since then, it remains open if there exists a mode of block ciphers to build quantum-secure tweakable block ciphers. This paper settles the problem in the reduction-based provable security paradigm. We show the first design of quantum-secure tweakable block ciphers based on quantum-secure block ciphers, and present a provable security bound. Our construction is simple, and when instantiated with a quantum-secure n-bit block cipher, it is secure against attacks that query arbitrary quantum superpositions of plaintexts and tweaks up to O(2n/6) quantum queries. Our security proofs use the compressed oracle technique introduced by Zhandry. More precisely, we use an alternative formalization of the technique introduced by Hosoyamada and Iwata.

scholarly journals Fundamental problems in provable security and cryptography

2006 ◽  
Vol 364 (1849) ◽  
pp. 3215-3230 ◽  
Author(s):  
Alexander W Dent
Keyword(s):  
Provable Security ◽  
Random Oracle Model ◽  
Random Oracle ◽  
New Approach ◽  
Active Research

This paper examines methods for formally proving the security of cryptographic schemes. We show that, despite many years of active research and dozens of significant results, there are fundamental problems which have yet to be solved. We also present a new approach to one of the more controversial aspects of provable security, the random oracle model.

scholarly journals The New Approach of AES Key Schedule for Lightweight Block Ciphers

2017 ◽  
Vol 19 (03) ◽  
pp. 21-26 ◽  
Author(s):  
Meltem Kurt Pehlivanoğlu ◽  
M. Tolga Sakalli ◽  
Nevcihan Duru ◽  
Fatma Büyüksaraçoğlu Sakalli
Keyword(s):  
Block Ciphers ◽  
New Approach ◽  
Key Schedule

scholarly journals Minimizing Key Materials: The Even–Mansour Cipher Revisited and Its Application to Lightweight Authenticated Encryption

2020 ◽  
Vol 2020 ◽  
pp. 1-6
Author(s):  
Ping Zhang ◽  
Qian Yuan
Keyword(s):  
Open Problem ◽  
Provable Security ◽  
Simple Structure ◽  
Block Ciphers ◽  
Authenticated Encryption ◽  
Maximal Multiplicity ◽  
Symmetric Key ◽  
Security Bound

The Even–Mansour cipher has been widely used in block ciphers and lightweight symmetric-key ciphers because of its simple structure and strict provable security. Its research has been a hot topic in cryptography. This paper focuses on the problem to minimize the key material of the Even–Mansour cipher while its security bound remains essentially the same. We introduce four structures of the Even–Mansour cipher with a short key and derive their security by Patarin’s H-coefficients technique. These four structures are proven secure up to O˜2k/μ adversarial queries, where k is the bit length of the key material and μ is the maximal multiplicity. Then, we apply them to lightweight authenticated encryption modes and prove their security up to about minb/2,c,k−log μ-bit adversarial queries, where b is the size of the permutation and c is the capacity of the permutation. Finally, we leave it as an open problem to settle the security of the t-round iterated Even–Mansour cipher with short keys.

scholarly journals A Brief Review on Methodology of Cryptanalysis

2019 ◽  
pp. 85-93
Author(s):  
K V Srinivasa Rao ◽  
M M Naidu ◽  
R. Satya Prasad
Keyword(s):  
Provable Security ◽  
Block Ciphers ◽  
Secret Key ◽  
Rigorous Analysis ◽  
Distinguishing Attack ◽  
Cipher Text ◽  
Security Models ◽  
Cryptographic Primitive ◽  
Symmetric Key

Cryptanalysis comes into deferent forms in order to support that rigorous analysis of the structure cryptographic primitive to evaluate and verify its claimed security margins. This analysis will follow the attack models represented previously in order to exploit possible weakness in the primitive. Thus, achieving the associated attack goals which will vary from a distinguishing attack to a total break that is defined based on the security margins or claims of the primitive under study. For example, for a hash function, total break constitutes finding a collision or obtaining the message from the hash value. While in block ciphers it revolves around recovering the secret key. When it comes to the claimed security margins, the design approaches will follow certain security models as in provable security or practical security or a mixture of both. The role of cryptanalyst is to subject these primitives to different existing categories of cryptanalysis approaches and tailor new ones that will push the design’s security margins if possible to new limits where these attacks are not applicable any more This chapter will introduce the prominent methods of cryptanalysis that utilize certain behavior in the cipher structure. Such behavior disturbs the assumed randomness of the output or the cipher text. This Paper will explore the basic definitions of prominent cryptanalysis methods that targets the specific structure of a cipher namely differential and linear cryptanalysis and their different variants. It will also discuss other potential crytpanalytic methods that are usually used in symmetric-key ciphers analysis especially block ciphers.

The conditions of provable security of block ciphers against truncated differential attack

2015 ◽  
Vol 52 (2) ◽  
pp. 176-184
Author(s):  
Victor Ruzhentsev
Keyword(s):  
Provable Security ◽  
Sufficient Conditions ◽  
Block Ciphers ◽  
Differential Attack ◽  
Differential Probability ◽  
Modified Method ◽  
Truncated Differential

The modified method of estimation of the resistance of block ciphers to truncated byte differential attack is proposed. The previously known method estimate the truncated byte differential probability for Rijndael-like ciphers. In this paper we spread the sphere of application of that method on wider class of ciphers. The proposed method based on searching the most probable truncated byte differential characteristics and verification of sufficient conditions of effective byte differentials absence.

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