Data Encryption Standard
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Cryptanalysis of Feistel Networks with Secret Round Functions Alex Biryukov, Gaëtan Leurent, Léo Perrin
Cryptanalysis of Feistel Networks with Secret Round Functions Alex Biryukov, Gaëtan Leurent, Léo Perrin To cite this version: Alex Biryukov, Gaëtan Leurent, Léo Perrin. Cryptanalysis of Feistel Networks with Secret Round Functions. Selected Areas in Cryptography - SAC 2015, Aug 2015, Sackville, Canada. hal-01243130 HAL Id: hal-01243130 https://hal.inria.fr/hal-01243130 Submitted on 14 Dec 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Cryptanalysis of Feistel Networks with Secret Round Functions ? Alex Biryukov1, Gaëtan Leurent2, and Léo Perrin3 1 [email protected], University of Luxembourg 2 [email protected], Inria, France 3 [email protected], SnT,University of Luxembourg Abstract. Generic distinguishers against Feistel Network with up to 5 rounds exist in the regular setting and up to 6 rounds in a multi-key setting. We present new cryptanalyses against Feistel Networks with 5, 6 and 7 rounds which are not simply distinguishers but actually recover completely the unknown Feistel functions. When an exclusive-or is used to combine the output of the round function with the other branch, we use the so-called yoyo game which we improved using a heuristic based on particular cycle structures. -
Improved Related-Key Attacks on DESX and DESX+
Improved Related-key Attacks on DESX and DESX+ Raphael C.-W. Phan1 and Adi Shamir3 1 Laboratoire de s´ecurit´eet de cryptographie (LASEC), Ecole Polytechnique F´ed´erale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland [email protected] 2 Faculty of Mathematics & Computer Science, The Weizmann Institute of Science, Rehovot 76100, Israel [email protected] Abstract. In this paper, we present improved related-key attacks on the original DESX, and DESX+, a variant of the DESX with its pre- and post-whitening XOR operations replaced with addition modulo 264. Compared to previous results, our attack on DESX has reduced text complexity, while our best attack on DESX+ eliminates the memory requirements at the same processing complexity. Keywords: DESX, DESX+, related-key attack, fault attack. 1 Introduction Due to the DES’ small key length of 56 bits, variants of the DES under multiple encryption have been considered, including double-DES under one or two 56-bit key(s), and triple-DES under two or three 56-bit keys. Another popular variant based on the DES is the DESX [15], where the basic keylength of single DES is extended to 120 bits by wrapping this DES with two outer pre- and post-whitening keys of 64 bits each. Also, the endorsement of single DES had been officially withdrawn by NIST in the summer of 2004 [19], due to its insecurity against exhaustive search. Future use of single DES is recommended only as a component of the triple-DES. This makes it more important to study the security of variants of single DES which increase the key length to avoid this attack. -
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. -
Rc-6 Cryptosystem in Vhdl
RC-6 CRYPTOSYSTEM IN VHDL BY:- Deepak Singh Samant OBJECTIVE: TO IMPLEMENT A CRYPTOSYSTEM USING RIVEST CIPHER-6 (RC6) ALGORITHM IN VHDL(FPGA) What is CRYPTOLOGY? CRYPTOGRAPHY is the art and science of achieving security by encoding message to make them non-readable . CRYPTANALYSIS is the technique of decoding messages from a non-readable format back to readable format without knowing how they were initially converted from readable format to non-readable format. CRYPTOGRAPHY + = CRYPTOLOGY CRYPTANALYSIS Cryptography Overview: Comm. E(k) N/W D(k) Key Set K Key Set K Types Of Attacks: . General View: 1.Criminal Attack 2.Publicity Attack 3.Legal Attack .Technical View: oPassive Attacks oActive Attacks Release of message Interruption Traffic Attacks Modification Fabrication Symmetric key cryptography If same key is used for encryption and decryption,we call the mechanism as symmetric key cryptography. It has the key distribution problem. Symmetric key cryptography Algorithm DES IDEA RC4 RC5 BLOW AES FISH AES: US government wanted to standardize a cryptographic algorithm,which was to be used universally by them.It was to be called as the Advanced Encryption Standard(AES). Among various proposal submitted,only 5 were short listed: 1.Rijndael 3.Serpent 5.MARS 2.Twofish 4.RC6 LITERATURE SURVEY • Comparison: (1) MARS: Its throughput in the studies was generally low. Therefore, its efficiency (throughput/area) was uniformly less than the other finalists. (2) RC6 throughput is generally average. RC6 seems to perform relatively better in pipelined implementations, non-feedback mode (3) Rijndael: good performance in fully pipelined implementations. Efficiency is generally very good. 4) Serpent: feedback mode encryption. -
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- -
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. -
Related-Key Statistical Cryptanalysis
Related-Key Statistical Cryptanalysis Darakhshan J. Mir∗ Poorvi L. Vora Department of Computer Science, Department of Computer Science, Rutgers, The State University of New Jersey George Washington University July 6, 2007 Abstract This paper presents the Cryptanalytic Channel Model (CCM). The model treats statistical key recovery as communication over a low capacity channel, where the channel and the encoding are determined by the cipher and the specific attack. A new attack, related-key recovery – the use of n related keys generated from k independent ones – is defined for all ciphers vulnera- ble to single-key recovery. Unlike classical related-key attacks such as differential related-key cryptanalysis, this attack does not exploit a special structural weakness in the cipher or key schedule, but amplifies the weakness exploited in the basic single key recovery. The related- key-recovery attack is shown to correspond to the use of a concatenated code over the channel, where the relationship among the keys determines the outer code, and the cipher and the attack the inner code. It is shown that there exists a relationship among keys for which the communi- cation complexity per bit of independent key is finite, for any probability of key recovery error. This may be compared to the unbounded communication complexity per bit of the single-key- recovery attack. The practical implications of this result are demonstrated through experiments on reduced-round DES. Keywords: related keys, concatenated codes, communication channel, statistical cryptanalysis, linear cryptanalysis, DES Communicating Author: Poorvi L. Vora, [email protected] ∗This work was done while the author was in the M.S. -
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. -
Serpent: a Proposal for the Advanced Encryption Standard
Serpent: A Proposal for the Advanced Encryption Standard Ross Anderson1 Eli Biham2 Lars Knudsen3 1 Cambridge University, England; email [email protected] 2 Technion, Haifa, Israel; email [email protected] 3 University of Bergen, Norway; email [email protected] Abstract. We propose a new block cipher as a candidate for the Ad- vanced Encryption Standard. Its design is highly conservative, yet still allows a very efficient implementation. It uses S-boxes similar to those of DES in a new structure that simultaneously allows a more rapid avalanche, a more efficient bitslice implementation, and an easy anal- ysis that enables us to demonstrate its security against all known types of attack. With a 128-bit block size and a 256-bit key, it is as fast as DES on the market leading Intel Pentium/MMX platforms (and at least as fast on many others); yet we believe it to be more secure than three-key triple-DES. 1 Introduction For many applications, the Data Encryption Standard algorithm is nearing the end of its useful life. Its 56-bit key is too small, as shown by a recent distributed key search exercise [28]. Although triple-DES can solve the key length problem, the DES algorithm was also designed primarily for hardware encryption, yet the great majority of applications that use it today implement it in software, where it is relatively inefficient. For these reasons, the US National Institute of Standards and Technology has issued a call for a successor algorithm, to be called the Advanced Encryption Standard or AES. -
Miss in the Middle
Miss in the middle By: Gal Leonard Keret Miss in the Middle Attacks on IDEA, Khufu and Khafre • Written by: – Prof. Eli Biham. – Prof. Alex Biryukov. – Prof. Adi Shamir. Introduction • So far we used traditional differential which predict and detect statistical events of highest possible probability. Introduction • A new approach is to search for events with probability one, whose condition cannot be met together (events that never happen). Impossible Differential • Random permutation: 휎 푀0 = 푎푛푦 퐶 표푓 푠푖푧푒 푀0. • Cipher (not perfect): 퐸 푀0 = 푠표푚푒 퐶 표푓 푠푖푧푒 푀0. • Events (푚 ↛ 푐) that never happen distinguish a cipher from a random permutation. Impossible Differential • Impossible events (푚 ↛ 푐) can help performing key elimination. • All the keys that lead to impossibility are obviously wrong. • This way we can filter wrong key guesses and leaving the correct key. Enigma – for example • Some of the attacks on Enigma were based on the observation that letters can not be encrypted to themselves. 퐸푛푖푔푚푎(푀0) ≠ 푀0 In General • (푀0, 퐶1) is a pair. If 푀0 푀0 → 퐶1. • 푀 ↛ 퐶 . 0 0 Some rounds For any key • ∀ 푘푒푦| 퐶1 → 퐶0 ↛ is an impossible key. Cannot lead to 퐶0. Some rounds Find each keys Decrypt 퐶1back to 퐶0. IDEA • International Data Encryption Algorithm. • First described in 1991. • Block cipher. • Symmetric. • Key sizes: 128 bits. • Block sizes: 64 bits. ⊕ - XOR. ⊞ - Addition modulo 216 ⊙ - Multiplication modulo 216+1 Encryption security • Combination of different mathematical groups. • Creation of "incompatibility“: ∗ • 푍216+1 → 푍216 ∗ • 푍216 → 푍216+1 ∗ ∗ Remark: 푍216+1 doesn’t contain 0 like 푍216 , so in 푍216+1 0 will be converted to 216 since 0 ≡ 216(푚표푑 216). -
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.