Linear Cryptanalysis of Non Binary Ciphers with an Application to SAFER
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Linear Cryptanalysis: Key Schedules and Tweakable Block Ciphers
Linear Cryptanalysis: Key Schedules and Tweakable Block Ciphers Thorsten Kranz, Gregor Leander and Friedrich Wiemer Horst Görtz Institute for IT Security, Ruhr-Universität Bochum, Germany {thorsten.kranz,gregor.leander,friedrich.wiemer}@rub.de Abstract. This paper serves as a systematization of knowledge of linear cryptanalysis and provides novel insights in the areas of key schedule design and tweakable block ciphers. We examine in a step by step manner the linear hull theorem in a general and consistent setting. Based on this, we study the influence of the choice of the key scheduling on linear cryptanalysis, a – notoriously difficult – but important subject. Moreover, we investigate how tweakable block ciphers can be analyzed with respect to linear cryptanalysis, a topic that surprisingly has not been scrutinized until now. Keywords: Linear Cryptanalysis · Key Schedule · Hypothesis of Independent Round Keys · Tweakable Block Cipher 1 Introduction Block ciphers are among the most important cryptographic primitives. Besides being used for encrypting the major fraction of our sensible data, they are important building blocks in many cryptographic constructions and protocols. Clearly, the security of any concrete block cipher can never be strictly proven, usually not even be reduced to a mathematical problem, i. e. be provable in the sense of provable cryptography. However, the concrete security of well-known ciphers, in particular the AES and its predecessor DES, is very well studied and probably much better scrutinized than many of the mathematical problems on which provable secure schemes are based on. This been said, there is a clear lack of understanding when it comes to the key schedule part of block ciphers. -
Related-Key Cryptanalysis of 3-WAY, Biham-DES,CAST, DES-X, Newdes, RC2, and TEA
Related-Key Cryptanalysis of 3-WAY, Biham-DES,CAST, DES-X, NewDES, RC2, and TEA John Kelsey Bruce Schneier David Wagner Counterpane Systems U.C. Berkeley kelsey,schneier @counterpane.com [email protected] f g Abstract. We present new related-key attacks on the block ciphers 3- WAY, Biham-DES, CAST, DES-X, NewDES, RC2, and TEA. Differen- tial related-key attacks allow both keys and plaintexts to be chosen with specific differences [KSW96]. Our attacks build on the original work, showing how to adapt the general attack to deal with the difficulties of the individual algorithms. We also give specific design principles to protect against these attacks. 1 Introduction Related-key cryptanalysis assumes that the attacker learns the encryption of certain plaintexts not only under the original (unknown) key K, but also under some derived keys K0 = f(K). In a chosen-related-key attack, the attacker specifies how the key is to be changed; known-related-key attacks are those where the key difference is known, but cannot be chosen by the attacker. We emphasize that the attacker knows or chooses the relationship between keys, not the actual key values. These techniques have been developed in [Knu93b, Bih94, KSW96]. Related-key cryptanalysis is a practical attack on key-exchange protocols that do not guarantee key-integrity|an attacker may be able to flip bits in the key without knowing the key|and key-update protocols that update keys using a known function: e.g., K, K + 1, K + 2, etc. Related-key attacks were also used against rotor machines: operators sometimes set rotors incorrectly. -
Differential-Linear Crypt Analysis
Differential-Linear Crypt analysis Susan K. Langfordl and Martin E. Hellman Department of Electrical Engineering Stanford University Stanford, CA 94035-4055 Abstract. This paper introduces a new chosen text attack on iterated cryptosystems, such as the Data Encryption Standard (DES). The attack is very efficient for 8-round DES,2 recovering 10 bits of key with 80% probability of success using only 512 chosen plaintexts. The probability of success increases to 95% using 768 chosen plaintexts. More key can be recovered with reduced probability of success. The attack takes less than 10 seconds on a SUN-4 workstation. While comparable in speed to existing attacks, this 8-round attack represents an order of magnitude improvement in the amount of required text. 1 Summary Iterated cryptosystems are encryption algorithms created by repeating a simple encryption function n times. Each iteration, or round, is a function of the previ- ous round’s oulpul and the key. Probably the best known algorithm of this type is the Data Encryption Standard (DES) [6].Because DES is widely used, it has been the focus of much of the research on the strength of iterated cryptosystems and is the system used as the sole example in this paper. Three major attacks on DES are exhaustive search [2, 71, Biham-Shamir’s differential cryptanalysis [l], and Matsui’s linear cryptanalysis [3, 4, 51. While exhaustive search is still the most practical attack for full 16 round DES, re- search interest is focused on the latter analytic attacks, in the hope or fear that improvements will render them practical as well. -
Report on the AES Candidates
Rep ort on the AES Candidates 1 2 1 3 Olivier Baudron , Henri Gilb ert , Louis Granb oulan , Helena Handschuh , 4 1 5 1 Antoine Joux , Phong Nguyen ,Fabrice Noilhan ,David Pointcheval , 1 1 1 1 Thomas Pornin , Guillaume Poupard , Jacques Stern , and Serge Vaudenay 1 Ecole Normale Sup erieure { CNRS 2 France Telecom 3 Gemplus { ENST 4 SCSSI 5 Universit e d'Orsay { LRI Contact e-mail: [email protected] Abstract This do cument rep orts the activities of the AES working group organized at the Ecole Normale Sup erieure. Several candidates are evaluated. In particular we outline some weaknesses in the designs of some candidates. We mainly discuss selection criteria b etween the can- didates, and make case-by-case comments. We nally recommend the selection of Mars, RC6, Serp ent, ... and DFC. As the rep ort is b eing nalized, we also added some new preliminary cryptanalysis on RC6 and Crypton in the App endix which are not considered in the main b o dy of the rep ort. Designing the encryption standard of the rst twentyyears of the twenty rst century is a challenging task: we need to predict p ossible future technologies, and wehavetotake unknown future attacks in account. Following the AES pro cess initiated by NIST, we organized an op en working group at the Ecole Normale Sup erieure. This group met two hours a week to review the AES candidates. The present do cument rep orts its results. Another task of this group was to up date the DFC candidate submitted by CNRS [16, 17] and to answer questions which had b een omitted in previous 1 rep orts on DFC. -
Linear (Hull) and Algebraic Cryptanalysis of the Block Cipher PRESENT
Linear (Hull) and Algebraic Cryptanalysis of the Block Cipher PRESENT Jorge Nakahara Jr1, Pouyan Sepehrdad1, Bingsheng Zhang2, Meiqin Wang3 1EPFL, Lausanne, Switzerland 2Cybernetica AS, Estonia and University of Tartu, Estonia 3Key Laboratory of Cryptologic Technology and Information Security, Ministry of Education, Shandong University, China Estonian Theory Days, 2-4.10.2009 Outline Why cryptanalysis?! Outline Outline Contributions The PRESENT Block Cipher Revisited Algebraic Cryptanalysis of PRESENT Linear Cryptanalysis of PRESENT Linear Hulls of PRESENT Conclusions Acknowledgements Outline Outline Contributions we performed linear analysis of reduced-round PRESENT exploiting fixed-points (and other symmetries) of pLayer exploiting low Hamming Weight bitmasks using iterative linear relations first linear hull analysis of PRESENT: 1st and 2nd best trails known-plaintext and ciphertext-only attack settings revisited algebraic analysis of 5-round PRESENT in less than 3 min best attacks on up to 26-round PRESENT (out of 31 rounds) Outline Outline The PRESENT Block Cipher block cipher designed by Bogdanov et al. at CHES’07 aimed at RFID tags, sensor networks (hardware environments) SPN structure 64-bit block size, 80- or 128-bit key size, 31 rounds one full round: xor with round subkey, S-box layer, bit permutation (pLayer) key schedule: 61-bit left rotation, S-box application, and xor with counter Outline Outline The PRESENT Block Cipher Computational graph of one full round of PRESENT Outline Outline Previous attack complexities on reduced-round -
Cryptanalysis of a Reduced Version of the Block Cipher E2
Cryptanalysis of a Reduced Version of the Block Cipher E2 Mitsuru Matsui and Toshio Tokita Information Technology R&D Center Mitsubishi Electric Corporation 5-1-1, Ofuna, Kamakura, Kanagawa, 247, Japan [email protected], [email protected] Abstract. This paper deals with truncated differential cryptanalysis of the 128-bit block cipher E2, which is an AES candidate designed and submitted by NTT. Our analysis is based on byte characteristics, where a difference of two bytes is simply encoded into one bit information “0” (the same) or “1” (not the same). Since E2 is a strongly byte-oriented algorithm, this bytewise treatment of characteristics greatly simplifies a description of its probabilistic behavior and noticeably enables us an analysis independent of the structure of its (unique) lookup table. As a result, we show a non-trivial seven round byte characteristic, which leads to a possible attack of E2 reduced to eight rounds without IT and FT by a chosen plaintext scenario. We also show that by a minor modification of the byte order of output of the round function — which does not reduce the complexity of the algorithm nor violates its design criteria at all —, a non-trivial nine round byte characteristic can be established, which results in a possible attack of the modified E2 reduced to ten rounds without IT and FT, and reduced to nine rounds with IT and FT. Our analysis does not have a serious impact on the full E2, since it has twelve rounds with IT and FT; however, our results show that the security level of the modified version against differential cryptanalysis is lower than the designers’ estimation. -
The Long Road to the Advanced Encryption Standard
The Long Road to the Advanced Encryption Standard Jean-Luc Cooke CertainKey Inc. [email protected], http://www.certainkey.com/˜jlcooke Abstract 1 Introduction This paper will start with a brief background of the Advanced Encryption Standard (AES) process, lessons learned from the Data Encryp- tion Standard (DES), other U.S. government Two decades ago the state-of-the-art in cryptographic publications and the fifteen first the private sector cryptography was—we round candidate algorithms. The focus of the know now—far behind the public sector. presentation will lie in presenting the general Don Coppersmith’s knowledge of the Data design of the five final candidate algorithms, Encryption Standard’s (DES) resilience to and the specifics of the AES and how it dif- the then unknown Differential Cryptanaly- fers from the Rijndael design. A presentation sis (DC), the design principles used in the on the AES modes of operation and Secure Secure Hash Algorithm (SHA) in Digital Hash Algorithm (SHA) family of algorithms Signature Standard (DSS) being case and will follow and will include discussion about point[NISTDSS][NISTDES][DC][NISTSHA1]. how it is directly implicated by AES develop- ments. The selection and design of the DES was shrouded in controversy and suspicion. This very controversy has lead to a fantastic acceler- Intended Audience ation in private sector cryptographic advance- ment. So intrigued by the NSA’s modifica- tions to the Lucifer algorithm, researchers— This paper was written as a supplement to a academic and industry alike—powerful tools presentation at the Ottawa International Linux in assessing block cipher strength were devel- Symposium. -
A Proposed SAFER Plus Security Algorithm Using Fast Walsh Hadamard Transform for Bluetooth Technology D.Sharmila 1, R.Neelaveni 2
International Journal of Wireless & Mobile Networks (IJWMN), Vol 1, No 2, November 2009 A Proposed SAFER Plus Security algorithm using Fast Walsh Hadamard transform for Bluetooth Technology D.Sharmila 1, R.Neelaveni 2 1(Research Scholar), Associate Professor, Bannari Amman Institute of Technology, Sathyamangalam. Tamil Nadu-638401. [email protected] 2 Asst.Prof. PSG College of Technology, Coimbatore.Tamil Nadu -638401. [email protected] ABSTRACT realtime two-way voice transfer providing data rates up to 3 Mb/s. It operates at 2.4 GHz frequency in the free ISM-band (Industrial, Scientific, and Medical) using frequency hopping In this paper, a modified SAFER plus algorithm is [18]. Bluetooth can be used to connect almost any kind of presented. Additionally, a comparison with various device to another device. Typical range of Bluetooth communication varies from 10 to 100 meters indoors. security algorithms like pipelined AES, Triple DES, Bluetooth technology and associated devices are susceptible Elliptic curve Diffie Hellman and the existing SAFER plus to general wireless networking threats, such as denial of service attacks, eavesdropping, man-in-the-middle attacks, are done. Performance of the algorithms is evaluated message modification, and resource misappropriation. They based on the data throughput, frequency and security are also threatened by more specific Bluetooth-related attacks that target known vulnerabilities in Bluetooth level. The results show that the modified SAFER plus implementations and specifications. Attacks against algorithm has enhanced security compared to the existing improperly secured Bluetooth implementations can provide attackers with unauthorized access to sensitive information algorithms. and unauthorized usage of Bluetooth devices and other Key words : Secure And Fast Encryption Routine, Triple Data systems or networks to which the devices are connected. -
Safer Than You Think! Revising the Transit Safety Narrative 1 September 2021
www.vtpi.org [email protected] 250-508-5150 Safer Than You Think! Revising the Transit Safety Narrative 1 September 2021 Todd Litman Victoria Transport Policy Institute Abstract Public transportation is overall a relatively safe (low crash risk) and secure (low crime risk) mode of transport. Transit travel has about a tenth the traffic casualty (death or injury) rate as automobile travel, and transit-oriented neighborhood residents have about a fifth the per capita crash casualty rate as in automobile-oriented areas. Transit also tends to have lower overall crime rates than automobile travel, and many transit service improvements can further increase security by improving surveillance and economic opportunities for at-risk populations. Despite its relative safety and security, many people consider public transit dangerous, and so are reluctant to use it or support service expansions in their communities. Various factors contribute to this excessive fear, including the nature of public transit travel, heavy media coverage of transit- related crashes and crimes, and conventional traffic safety messages which emphasize danger rather than safety. Transit agencies can help create a new safety narrative by better measuring and communicating transit’s overall safety and security impacts, and providing better guidance concerning how users and communities can enhance transit safety and security. A summary version of this report was published as, “A New Transit Safety Narrative” Journal of Public Transportation, Vol. 17, No. 4, 2014, pp.121-142; at www.nctr.usf.edu/wp-content/uploads/2014/12/JPT17.4_Litman.pdf. It was also published as, The Hidden Traffic Safety Solution: Public Transportation, American Public Transportation Association (www.apta.com); at www.apta.com/mediacenter/pressreleases/2016/Pages/Hidden-Traffic-Safety-Solution.aspx Todd Litman 2013-2021 You are welcome and encouraged to copy, distribute, share and excerpt this document and its ideas, provided the author is given attribution. -
Elastic Block Ciphers: the Basic Design
Elastic Block Ciphers: The Basic Design ∗ † Debra Cook Angelos Keromytis Moti Yung Bell Labs Columbia University RSA Labs, EMC Corp, and Murray Hill, NJ, USA Dept. of Computer Science Columbia University [email protected] New York, NY, USA Dept. of Computer Science [email protected] [email protected] ABSTRACT We introduce the concept of an elastic block cipher, which We introduce the concept of an elastic block cipher, which allows us to ”stretch” the supported block size of a block refers to stretching the supported block size of a block ci- cipher up to a length double the original block size, while pher to any length up to twice the original block size while increasing the computational workload proportionally to the incurring a computational workload that is proportional to block size. This, together with modes of operation, permits the block size. We define a method for converting any ex- block sizes to be set based on an application’s requirements, isting block cipher into an elastic block cipher and mention allowing, for example, a non-traditional block size to be used our analysis of the construction. for all blocks, or a traditional block size to be used for all but the last block in a given mode of operation. We pro- Categories and Subject Descriptors pose a general method for creating an elastic block cipher E.0 [General]: Data Encryption from an existing block cipher. Our intent is not to design a new ad-hoc cipher, but to systematically build upon existing General Terms block ciphers. Our method consists of a network structure block ciphers, algorithms, encryption that uses the round function from an existing block cipher, allowing us to treat the round function of the original ci- Keywords pher as a black box and reuse its properties. -
Linear Cryptanalysis of DES with Asymmetries
Linear Cryptanalysis of DES with Asymmetries Andrey Bogdanov and Philip S. Vejre Technical University of Denmark {anbog,psve}@dtu.dk Abstract. Linear cryptanalysis of DES, proposed by Matsui in 1993, has had a seminal impact on symmetric-key cryptography, having seen massive research efforts over the past two decades. It has spawned many variants, including multidimensional and zero-correlation linear crypt- analysis. These variants can claim best attacks on several ciphers, in- cluding present, Serpent, and CLEFIA. For DES, none of these vari- ants have improved upon Matsui’s original linear cryptanalysis, which has been the best known-plaintext key-recovery attack on the cipher ever since. In a revisit, Junod concluded that when using 243 known plain- texts, this attack has a complexity of 241 DES evaluations. His analysis relies on the standard assumptions of right-key equivalence and wrong- key randomisation. In this paper, we first investigate the validity of these fundamental as- sumptions when applied to DES. For the right key, we observe that strong linear approximations of DES have more than just one dominant trail and, thus, that the right keys are in fact inequivalent with respect to linear correlation. We therefore develop a new right-key model us- ing Gaussian mixtures for approximations with several dominant trails. For the wrong key, we observe that the correlation of a strong approx- imation after the partial decryption with a wrong key still shows much non-randomness. To remedy this, we propose a novel wrong-key model that expresses the wrong-key linear correlation using a version of DES with more rounds. -
Identifying Open Research Problems in Cryptography by Surveying Cryptographic Functions and Operations 1
International Journal of Grid and Distributed Computing Vol. 10, No. 11 (2017), pp.79-98 http://dx.doi.org/10.14257/ijgdc.2017.10.11.08 Identifying Open Research Problems in Cryptography by Surveying Cryptographic Functions and Operations 1 Rahul Saha1, G. Geetha2, Gulshan Kumar3 and Hye-Jim Kim4 1,3School of Computer Science and Engineering, Lovely Professional University, Punjab, India 2Division of Research and Development, Lovely Professional University, Punjab, India 4Business Administration Research Institute, Sungshin W. University, 2 Bomun-ro 34da gil, Seongbuk-gu, Seoul, Republic of Korea Abstract Cryptography has always been a core component of security domain. Different security services such as confidentiality, integrity, availability, authentication, non-repudiation and access control, are provided by a number of cryptographic algorithms including block ciphers, stream ciphers and hash functions. Though the algorithms are public and cryptographic strength depends on the usage of the keys, the ciphertext analysis using different functions and operations used in the algorithms can lead to the path of revealing a key completely or partially. It is hard to find any survey till date which identifies different operations and functions used in cryptography. In this paper, we have categorized our survey of cryptographic functions and operations in the algorithms in three categories: block ciphers, stream ciphers and cryptanalysis attacks which are executable in different parts of the algorithms. This survey will help the budding researchers in the society of crypto for identifying different operations and functions in cryptographic algorithms. Keywords: cryptography; block; stream; cipher; plaintext; ciphertext; functions; research problems 1. Introduction Cryptography [1] in the previous time was analogous to encryption where the main task was to convert the readable message to an unreadable format.