Data Encryption Standard
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Improved Cryptanalysis of the Reduced Grøstl Compression Function, ECHO Permutation and AES Block Cipher
Improved Cryptanalysis of the Reduced Grøstl Compression Function, ECHO Permutation and AES Block Cipher Florian Mendel1, Thomas Peyrin2, Christian Rechberger1, and Martin Schl¨affer1 1 IAIK, Graz University of Technology, Austria 2 Ingenico, France [email protected],[email protected] Abstract. In this paper, we propose two new ways to mount attacks on the SHA-3 candidates Grøstl, and ECHO, and apply these attacks also to the AES. Our results improve upon and extend the rebound attack. Using the new techniques, we are able to extend the number of rounds in which available degrees of freedom can be used. As a result, we present the first attack on 7 rounds for the Grøstl-256 output transformation3 and improve the semi-free-start collision attack on 6 rounds. Further, we present an improved known-key distinguisher for 7 rounds of the AES block cipher and the internal permutation used in ECHO. Keywords: hash function, block cipher, cryptanalysis, semi-free-start collision, known-key distinguisher 1 Introduction Recently, a new wave of hash function proposals appeared, following a call for submissions to the SHA-3 contest organized by NIST [26]. In order to analyze these proposals, the toolbox which is at the cryptanalysts' disposal needs to be extended. Meet-in-the-middle and differential attacks are commonly used. A recent extension of differential cryptanalysis to hash functions is the rebound attack [22] originally applied to reduced (7.5 rounds) Whirlpool (standardized since 2000 by ISO/IEC 10118-3:2004) and a reduced version (6 rounds) of the SHA-3 candidate Grøstl-256 [14], which both have 10 rounds in total. -
Public-Key Cryptography
Public Key Cryptography EJ Jung Basic Public Key Cryptography public key public key ? private key Alice Bob Given: Everybody knows Bob’s public key - How is this achieved in practice? Only Bob knows the corresponding private key Goals: 1. Alice wants to send a secret message to Bob 2. Bob wants to authenticate himself Requirements for Public-Key Crypto ! Key generation: computationally easy to generate a pair (public key PK, private key SK) • Computationally infeasible to determine private key PK given only public key PK ! Encryption: given plaintext M and public key PK, easy to compute ciphertext C=EPK(M) ! Decryption: given ciphertext C=EPK(M) and private key SK, easy to compute plaintext M • Infeasible to compute M from C without SK • Decrypt(SK,Encrypt(PK,M))=M Requirements for Public-Key Cryptography 1. Computationally easy for a party B to generate a pair (public key KUb, private key KRb) 2. Easy for sender to generate ciphertext: C = EKUb (M ) 3. Easy for the receiver to decrypt ciphertect using private key: M = DKRb (C) = DKRb[EKUb (M )] Henric Johnson 4 Requirements for Public-Key Cryptography 4. Computationally infeasible to determine private key (KRb) knowing public key (KUb) 5. Computationally infeasible to recover message M, knowing KUb and ciphertext C 6. Either of the two keys can be used for encryption, with the other used for decryption: M = DKRb[EKUb (M )] = DKUb[EKRb (M )] Henric Johnson 5 Public-Key Cryptographic Algorithms ! RSA and Diffie-Hellman ! RSA - Ron Rives, Adi Shamir and Len Adleman at MIT, in 1977. • RSA -
Key-Dependent Approximations in Cryptanalysis. an Application of Multiple Z4 and Non-Linear Approximations
KEY-DEPENDENT APPROXIMATIONS IN CRYPTANALYSIS. AN APPLICATION OF MULTIPLE Z4 AND NON-LINEAR APPROXIMATIONS. FX Standaert, G Rouvroy, G Piret, JJ Quisquater, JD Legat Universite Catholique de Louvain, UCL Crypto Group, Place du Levant, 3, 1348 Louvain-la-Neuve, standaert,rouvroy,piret,quisquater,[email protected] Linear cryptanalysis is a powerful cryptanalytic technique that makes use of a linear approximation over some rounds of a cipher, combined with one (or two) round(s) of key guess. This key guess is usually performed by a partial decryp- tion over every possible key. In this paper, we investigate a particular class of non-linear boolean functions that allows to mount key-dependent approximations of s-boxes. Replacing the classical key guess by these key-dependent approxima- tions allows to quickly distinguish a set of keys including the correct one. By combining different relations, we can make up a system of equations whose solu- tion is the correct key. The resulting attack allows larger flexibility and improves the success rate in some contexts. We apply it to the block cipher Q. In parallel, we propose a chosen-plaintext attack against Q that reduces the required number of plaintext-ciphertext pairs from 297 to 287. 1. INTRODUCTION In its basic version, linear cryptanalysis is a known-plaintext attack that uses a linear relation between input-bits, output-bits and key-bits of an encryption algorithm that holds with a certain probability. If enough plaintext-ciphertext pairs are provided, this approximation can be used to assign probabilities to the possible keys and to locate the most probable one. -
Basic Cryptography
Basic cryptography • How cryptography works... • Symmetric cryptography... • Public key cryptography... • Online Resources... • Printed Resources... I VP R 1 © Copyright 2002-2007 Haim Levkowitz How cryptography works • Plaintext • Ciphertext • Cryptographic algorithm • Key Decryption Key Algorithm Plaintext Ciphertext Encryption I VP R 2 © Copyright 2002-2007 Haim Levkowitz Simple cryptosystem ... ! ABCDEFGHIJKLMNOPQRSTUVWXYZ ! DEFGHIJKLMNOPQRSTUVWXYZABC • Caesar Cipher • Simple substitution cipher • ROT-13 • rotate by half the alphabet • A => N B => O I VP R 3 © Copyright 2002-2007 Haim Levkowitz Keys cryptosystems … • keys and keyspace ... • secret-key and public-key ... • key management ... • strength of key systems ... I VP R 4 © Copyright 2002-2007 Haim Levkowitz Keys and keyspace … • ROT: key is N • Brute force: 25 values of N • IDEA (international data encryption algorithm) in PGP: 2128 numeric keys • 1 billion keys / sec ==> >10,781,000,000,000,000,000,000 years I VP R 5 © Copyright 2002-2007 Haim Levkowitz Symmetric cryptography • DES • Triple DES, DESX, GDES, RDES • RC2, RC4, RC5 • IDEA Key • Blowfish Plaintext Encryption Ciphertext Decryption Plaintext Sender Recipient I VP R 6 © Copyright 2002-2007 Haim Levkowitz DES • Data Encryption Standard • US NIST (‘70s) • 56-bit key • Good then • Not enough now (cracked June 1997) • Discrete blocks of 64 bits • Often w/ CBC (cipherblock chaining) • Each blocks encr. depends on contents of previous => detect missing block I VP R 7 © Copyright 2002-2007 Haim Levkowitz Triple DES, DESX, -
A Quantitative Study of Advanced Encryption Standard Performance
United States Military Academy USMA Digital Commons West Point ETD 12-2018 A Quantitative Study of Advanced Encryption Standard Performance as it Relates to Cryptographic Attack Feasibility Daniel Hawthorne United States Military Academy, [email protected] Follow this and additional works at: https://digitalcommons.usmalibrary.org/faculty_etd Part of the Information Security Commons Recommended Citation Hawthorne, Daniel, "A Quantitative Study of Advanced Encryption Standard Performance as it Relates to Cryptographic Attack Feasibility" (2018). West Point ETD. 9. https://digitalcommons.usmalibrary.org/faculty_etd/9 This Doctoral Dissertation is brought to you for free and open access by USMA Digital Commons. It has been accepted for inclusion in West Point ETD by an authorized administrator of USMA Digital Commons. For more information, please contact [email protected]. A QUANTITATIVE STUDY OF ADVANCED ENCRYPTION STANDARD PERFORMANCE AS IT RELATES TO CRYPTOGRAPHIC ATTACK FEASIBILITY A Dissertation Presented in Partial Fulfillment of the Requirements for the Degree of Doctor of Computer Science By Daniel Stephen Hawthorne Colorado Technical University December, 2018 Committee Dr. Richard Livingood, Ph.D., Chair Dr. Kelly Hughes, DCS, Committee Member Dr. James O. Webb, Ph.D., Committee Member December 17, 2018 © Daniel Stephen Hawthorne, 2018 1 Abstract The advanced encryption standard (AES) is the premier symmetric key cryptosystem in use today. Given its prevalence, the security provided by AES is of utmost importance. Technology is advancing at an incredible rate, in both capability and popularity, much faster than its rate of advancement in the late 1990s when AES was selected as the replacement standard for DES. Although the literature surrounding AES is robust, most studies fall into either theoretical or practical yet infeasible. -
Public Key Cryptography And
PublicPublic KeyKey CryptographyCryptography andand RSARSA Raj Jain Washington University in Saint Louis Saint Louis, MO 63130 [email protected] Audio/Video recordings of this lecture are available at: http://www.cse.wustl.edu/~jain/cse571-11/ Washington University in St. Louis CSE571S ©2011 Raj Jain 9-1 OverviewOverview 1. Public Key Encryption 2. Symmetric vs. Public-Key 3. RSA Public Key Encryption 4. RSA Key Construction 5. Optimizing Private Key Operations 6. RSA Security These slides are based partly on Lawrie Brown’s slides supplied with William Stallings’s book “Cryptography and Network Security: Principles and Practice,” 5th Ed, 2011. Washington University in St. Louis CSE571S ©2011 Raj Jain 9-2 PublicPublic KeyKey EncryptionEncryption Invented in 1975 by Diffie and Hellman at Stanford Encrypted_Message = Encrypt(Key1, Message) Message = Decrypt(Key2, Encrypted_Message) Key1 Key2 Text Ciphertext Text Keys are interchangeable: Key2 Key1 Text Ciphertext Text One key is made public while the other is kept private Sender knows only public key of the receiver Asymmetric Washington University in St. Louis CSE571S ©2011 Raj Jain 9-3 PublicPublic KeyKey EncryptionEncryption ExampleExample Rivest, Shamir, and Adleman at MIT RSA: Encrypted_Message = m3 mod 187 Message = Encrypted_Message107 mod 187 Key1 = <3,187>, Key2 = <107,187> Message = 5 Encrypted Message = 53 = 125 Message = 125107 mod 187 = 5 = 125(64+32+8+2+1) mod 187 = {(12564 mod 187)(12532 mod 187)... (1252 mod 187)(125 mod 187)} mod 187 Washington University in -
The Data Encryption Standard (DES) – History
Chair for Network Architectures and Services Department of Informatics TU München – Prof. Carle Network Security Chapter 2 Basics 2.1 Symmetric Cryptography • Overview of Cryptographic Algorithms • Attacking Cryptographic Algorithms • Historical Approaches • Foundations of Modern Cryptography • Modes of Encryption • Data Encryption Standard (DES) • Advanced Encryption Standard (AES) Cryptographic algorithms: outline Cryptographic Algorithms Symmetric Asymmetric Cryptographic Overview En- / Decryption En- / Decryption Hash Functions Modes of Cryptanalysis Background MDC’s / MACs Operation Properties DES RSA MD-5 AES Diffie-Hellman SHA-1 RC4 ElGamal CBC-MAC Network Security, WS 2010/11, Chapter 2.1 2 Basic Terms: Plaintext and Ciphertext Plaintext P The original readable content of a message (or data). P_netsec = „This is network security“ Ciphertext C The encrypted version of the plaintext. C_netsec = „Ff iThtIiDjlyHLPRFxvowf“ encrypt key k1 C P key k2 decrypt In case of symmetric cryptography, k1 = k2. Network Security, WS 2010/11, Chapter 2.1 3 Basic Terms: Block cipher and Stream cipher Block cipher A cipher that encrypts / decrypts inputs of length n to outputs of length n given the corresponding key k. • n is block length Most modern symmetric ciphers are block ciphers, e.g. AES, DES, Twofish, … Stream cipher A symmetric cipher that generats a random bitstream, called key stream, from the symmetric key k. Ciphertext = key stream XOR plaintext Network Security, WS 2010/11, Chapter 2.1 4 Cryptographic algorithms: overview -
Blockchain Beyond Cryptocurrency Or Is Private Chain a Hoax Or How I Lose Money in Bitcoin but Still Decide to Get in the Research
Blockchain Beyond Cryptocurrency Or Is Private Chain a Hoax Or How I Lose Money in Bitcoin but still Decide to Get in the Research Hong Wan Edward P. Fitts Department of Industrial and Systems Engineering Sept 2019 In this talk: • Blockchain and trust • Different kinds of blockchain • Cases and Examples • Discussions First Things First https://images.app.goo.gl/JuNznV8dZKTaHWEf9 Disclaimer Block and Chain https://youtu.be/SSo_EIwHSd4 https://youtu.be/SSo_EIwHSd4 Blockchain Design Questions • Who can access data: Private vs. Public • Who can validate data/add block: Permissioned vs Permissionless • Consensus to be used: Trade-off among security and efficiency. https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=2ahUKEwinjN2s7_DkAhXlmeAKHXxhAIUQjRx6BAgBEAQ&url=ht tps%3A%2F%2F101blockchains.com%2Fconsensus-algorithms-blockchain%2F&psig=AOvVaw23pKh4qS8W_xgyajJ3aFl9&ust=1569669093339830 Bad News First • “Private blockchains are completely uninteresting… -- the only reason to operate one is to ride on the blockchain hype…” Bruce Schneier Tonight we will talk about cryptocurrencies… .everything you don’t understand money combined by everything you don’t understand about computers…. Cryptocurrencies: Last Week Tonight with John Oliver (HBO) https://www.schneier.com/blog/archives/2019/02/blockchain_and_.html http://shorturl.at/ahsRU, shorturl.at/gETV2 https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=2ahUKEwj- https://d279m997dpfwgl.cloudfront.net/wp/2017/11/Trustp72L7vDkAhVjQt8KHU18CjsQjRx6BAgBEAQ&url=https%3A%2F%2Fwww.wbur.org%2Fonpoint%2F2017%2F11%2F20%2Fwho-can-cropped.jpg-you- -
Chapter 3 – Block Ciphers and the Data Encryption Standard
Chapter 3 –Block Ciphers and the Data Cryptography and Network Encryption Standard Security All the afternoon Mungo had been working on Stern's Chapter 3 code, principally with the aid of the latest messages which he had copied down at the Nevin Square drop. Stern was very confident. He must be well aware London Central knew about that drop. It was obvious Fifth Edition that they didn't care how often Mungo read their messages, so confident were they in the by William Stallings impenetrability of the code. —Talking to Strange Men, Ruth Rendell Lecture slides by Lawrie Brown Modern Block Ciphers Block vs Stream Ciphers now look at modern block ciphers • block ciphers process messages in blocks, each one of the most widely used types of of which is then en/decrypted cryptographic algorithms • like a substitution on very big characters provide secrecy /hii/authentication services – 64‐bits or more focus on DES (Data Encryption Standard) • stream ciphers process messages a bit or byte at a time when en/decrypting to illustrate block cipher design principles • many current ciphers are block ciphers – better analysed – broader range of applications Block vs Stream Ciphers Block Cipher Principles • most symmetric block ciphers are based on a Feistel Cipher Structure • needed since must be able to decrypt ciphertext to recover messages efficiently • bloc k cihiphers lklook like an extremely large substitution • would need table of 264 entries for a 64‐bit block • instead create from smaller building blocks • using idea of a product cipher 1 Claude -
Impossible Differentials in Twofish
Twofish Technical Report #5 Impossible differentials in Twofish Niels Ferguson∗ October 19, 1999 Abstract We show how an impossible-differential attack, first applied to DEAL by Knudsen, can be applied to Twofish. This attack breaks six rounds of the 256-bit key version using 2256 steps; it cannot be extended to seven or more Twofish rounds. Keywords: Twofish, cryptography, cryptanalysis, impossible differential, block cipher, AES. Current web site: http://www.counterpane.com/twofish.html 1 Introduction 2.1 Twofish as a pure Feistel cipher Twofish is one of the finalists for the AES [SKW+98, As mentioned in [SKW+98, section 7.9] and SKW+99]. In [Knu98a, Knu98b] Lars Knudsen used [SKW+99, section 7.9.3] we can rewrite Twofish to a 5-round impossible differential to attack DEAL. be a pure Feistel cipher. We will demonstrate how Eli Biham, Alex Biryukov, and Adi Shamir gave the this is done. The main idea is to save up all the ro- technique the name of `impossible differential', and tations until just before the output whitening, and applied it with great success to Skipjack [BBS99]. apply them there. We will use primes to denote the In this report we show how Knudsen's attack can values in our new representation. We start with the be applied to Twofish. We use the notation from round values: [SKW+98] and [SKW+99]; readers not familiar with R0 = ROL(Rr;0; (r + 1)=2 ) the notation should consult one of these references. r;0 b c R0 = ROR(Rr;1; (r + 1)=2 ) r;1 b c R0 = ROL(Rr;2; r=2 ) 2 The attack r;2 b c R0 = ROR(Rr;3; r=2 ) r;3 b c Knudsen's 5-round impossible differential works for To get the same output we update the rule to com- any Feistel cipher where the round function is in- pute the output whitening. -
Block Ciphers and the Data Encryption Standard
Lecture 3: Block Ciphers and the Data Encryption Standard Lecture Notes on “Computer and Network Security” by Avi Kak ([email protected]) January 26, 2021 3:43pm ©2021 Avinash Kak, Purdue University Goals: To introduce the notion of a block cipher in the modern context. To talk about the infeasibility of ideal block ciphers To introduce the notion of the Feistel Cipher Structure To go over DES, the Data Encryption Standard To illustrate important DES steps with Python and Perl code CONTENTS Section Title Page 3.1 Ideal Block Cipher 3 3.1.1 Size of the Encryption Key for the Ideal Block Cipher 6 3.2 The Feistel Structure for Block Ciphers 7 3.2.1 Mathematical Description of Each Round in the 10 Feistel Structure 3.2.2 Decryption in Ciphers Based on the Feistel Structure 12 3.3 DES: The Data Encryption Standard 16 3.3.1 One Round of Processing in DES 18 3.3.2 The S-Box for the Substitution Step in Each Round 22 3.3.3 The Substitution Tables 26 3.3.4 The P-Box Permutation in the Feistel Function 33 3.3.5 The DES Key Schedule: Generating the Round Keys 35 3.3.6 Initial Permutation of the Encryption Key 38 3.3.7 Contraction-Permutation that Generates the 48-Bit 42 Round Key from the 56-Bit Key 3.4 What Makes DES a Strong Cipher (to the 46 Extent It is a Strong Cipher) 3.5 Homework Problems 48 2 Computer and Network Security by Avi Kak Lecture 3 Back to TOC 3.1 IDEAL BLOCK CIPHER In a modern block cipher (but still using a classical encryption method), we replace a block of N bits from the plaintext with a block of N bits from the ciphertext. -
Constructing Low-Weight Dth-Order Correlation-Immune Boolean Functions Through the Fourier-Hadamard Transform Claude Carlet and Xi Chen*
1 Constructing low-weight dth-order correlation-immune Boolean functions through the Fourier-Hadamard transform Claude Carlet and Xi Chen* Abstract The correlation immunity of Boolean functions is a property related to cryptography, to error correcting codes, to orthogonal arrays (in combinatorics, which was also a domain of interest of S. Golomb) and in a slightly looser way to sequences. Correlation-immune Boolean functions (in short, CI functions) have the property of keeping the same output distribution when some input variables are fixed. They have been widely used as combiners in stream ciphers to allow resistance to the Siegenthaler correlation attack. Very recently, a new use of CI functions has appeared in the framework of side channel attacks (SCA). To reduce the cost overhead of counter-measures to SCA, CI functions need to have low Hamming weights. This actually poses new challenges since the known constructions which are based on properties of the Walsh-Hadamard transform, do not allow to build unbalanced CI functions. In this paper, we propose constructions of low-weight dth-order CI functions based on the Fourier- Hadamard transform, while the known constructions of resilient functions are based on the Walsh-Hadamard transform. We first prove a simple but powerful result, which makes that one only need to consider the case where d is odd in further research. Then we investigate how constructing low Hamming weight CI functions through the Fourier-Hadamard transform (which behaves well with respect to the multiplication of Boolean functions). We use the characterization of CI functions by the Fourier-Hadamard transform and introduce a related general construction of CI functions by multiplication.