Hardware Implementation of the Salsa20 and Phelix Stream Ciphers
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Failures of Secret-Key Cryptography D
Failures of secret-key cryptography D. J. Bernstein University of Illinois at Chicago & Technische Universiteit Eindhoven http://xkcd.com/538/ 2011 Grigg{Gutmann: In the past 15 years \no one ever lost money to an attack on a properly designed cryptosystem (meaning one that didn't use homebrew crypto or toy keys) in the Internet or commercial worlds". 2011 Grigg{Gutmann: In the past 15 years \no one ever lost money to an attack on a properly designed cryptosystem (meaning one that didn't use homebrew crypto or toy keys) in the Internet or commercial worlds". 2002 Shamir:\Cryptography is usually bypassed. I am not aware of any major world-class security system employing cryptography in which the hackers penetrated the system by actually going through the cryptanalysis." Do these people mean that it's actually infeasible to break real-world crypto? Do these people mean that it's actually infeasible to break real-world crypto? Or do they mean that breaks are feasible but still not worthwhile for the attackers? Do these people mean that it's actually infeasible to break real-world crypto? Or do they mean that breaks are feasible but still not worthwhile for the attackers? Or are they simply wrong: real-world crypto is breakable; is in fact being broken; is one of many ongoing disaster areas in security? Do these people mean that it's actually infeasible to break real-world crypto? Or do they mean that breaks are feasible but still not worthwhile for the attackers? Or are they simply wrong: real-world crypto is breakable; is in fact being broken; is one of many ongoing disaster areas in security? Let's look at some examples. -
Key Differentiation Attacks on Stream Ciphers
Key differentiation attacks on stream ciphers Abstract In this paper the applicability of differential cryptanalytic tool to stream ciphers is elaborated using the algebraic representation similar to early Shannon’s postulates regarding the concept of confusion. In 2007, Biham and Dunkelman [3] have formally introduced the concept of differential cryptanalysis in stream ciphers by addressing the three different scenarios of interest. Here we mainly consider the first scenario where the key difference and/or IV difference influence the internal state of the cipher (∆key, ∆IV ) → ∆S. We then show that under certain circumstances a chosen IV attack may be transformed in the key chosen attack. That is, whenever at some stage of the key/IV setup algorithm (KSA) we may identify linear relations between some subset of key and IV bits, and these key variables only appear through these linear relations, then using the differentiation of internal state variables (through chosen IV scenario of attack) we are able to eliminate the presence of corresponding key variables. The method leads to an attack whose complexity is beyond the exhaustive search, whenever the cipher admits exact algebraic description of internal state variables and the keystream computation is not complex. A successful application is especially noted in the context of stream ciphers whose keystream bits evolve relatively slow as a function of secret state bits. A modification of the attack can be applied to the TRIVIUM stream cipher [8], in this case 12 linear relations could be identified but at the same time the same 12 key variables appear in another part of state register. -
Ensuring Fast Implementations of Symmetric Ciphers on the Intel Pentium 4 and Beyond
This may be the author’s version of a work that was submitted/accepted for publication in the following source: Henricksen, Matthew& Dawson, Edward (2006) Ensuring Fast Implementations of Symmetric Ciphers on the Intel Pentium 4 and Beyond. Lecture Notes in Computer Science, 4058, Article number: AISP52-63. This file was downloaded from: https://eprints.qut.edu.au/24788/ c Consult author(s) regarding copyright matters This work is covered by copyright. Unless the document is being made available under a Creative Commons Licence, you must assume that re-use is limited to personal use and that permission from the copyright owner must be obtained for all other uses. If the docu- ment is available under a Creative Commons License (or other specified license) then refer to the Licence for details of permitted re-use. It is a condition of access that users recog- nise and abide by the legal requirements associated with these rights. If you believe that this work infringes copyright please provide details by email to [email protected] Notice: Please note that this document may not be the Version of Record (i.e. published version) of the work. Author manuscript versions (as Sub- mitted for peer review or as Accepted for publication after peer review) can be identified by an absence of publisher branding and/or typeset appear- ance. If there is any doubt, please refer to the published source. https://doi.org/10.1007/11780656_5 Ensuring Fast Implementations of Symmetric Ciphers on the Intel Pentium 4 and Beyond Matt Henricksen and Ed Dawson Information Security Institute, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland, 4001, Australia. -
Stream Ciphers (Contd.)
Stream Ciphers (contd.) Debdeep Mukhopadhyay Assistant Professor Department of Computer Science and Engineering Indian Institute of Technology Kharagpur INDIA -721302 Objectives • Non-linear feedback shift registers • Stream ciphers using LFSRs: – Non-linear combination generators – Non-linear filter generators – Clock controlled generators – Other Stream Ciphers Low Power Ajit Pal IIT Kharagpur 1 Non-linear feedback shift registers • A Feedback Shift Register (FSR) is non-singular iff for all possible initial states every output sequence of the FSR is periodic. de Bruijn Sequence An FSR with feedback function fs(jj−−12 , s ,..., s jL − ) is non-singular iff f is of the form: fs=⊕jL−−−−+ gss( j12 , j ,..., s jL 1 ) for some Boolean function g. The period of a non-singular FSR with length L is at most 2L . If the period of the output sequence for any initial state of a non-singular FSR of length L is 2L , then the FSR is called a de Bruijn FSR, and the output sequence is called a de Bruijn sequence. Low Power Ajit Pal IIT Kharagpur 2 Example f (,xxx123 , )1= ⊕⊕⊕ x 2 x 3 xx 12 t x1 x2 x3 t x1 x2 x3 0 0 0 0 4 0 1 1 1 1 0 0 5 1 0 1 2 1 1 0 6 0 1 0 3 1 1 1 3 0 0 1 Converting a maximal length LFSR to a de-Bruijn FSR Let R1 be a maximum length LFSR of length L with linear feedback function: fs(jj−−12 , s ,..., s jL − ). Then the FSR R2 with feedback function: gs(jj−−12 , s ,..., s jL − )=⊕ f sjj−−12 , s ,..., s j −L+1 is a de Bruijn FSR. -
RC4-2S: RC4 Stream Cipher with Two State Tables
RC4-2S: RC4 Stream Cipher with Two State Tables Maytham M. Hammood, Kenji Yoshigoe and Ali M. Sagheer Abstract One of the most important symmetric cryptographic algorithms is Rivest Cipher 4 (RC4) stream cipher which can be applied to many security applications in real time security. However, RC4 cipher shows some weaknesses including a correlation problem between the public known outputs of the internal state. We propose RC4 stream cipher with two state tables (RC4-2S) as an enhancement to RC4. RC4-2S stream cipher system solves the correlation problem between the public known outputs of the internal state using permutation between state 1 (S1) and state 2 (S2). Furthermore, key generation time of the RC4-2S is faster than that of the original RC4 due to less number of operations per a key generation required by the former. The experimental results confirm that the output streams generated by the RC4-2S are more random than that generated by RC4 while requiring less time than RC4. Moreover, RC4-2S’s high resistivity protects against many attacks vulnerable to RC4 and solves several weaknesses of RC4 such as distinguishing attack. Keywords Stream cipher Á RC4 Á Pseudo-random number generator This work is based in part, upon research supported by the National Science Foundation (under Grant Nos. CNS-0855248 and EPS-0918970). Any opinions, findings and conclusions or recommendations expressed in this material are those of the author (s) and do not necessarily reflect the views of the funding agencies or those of the employers. M. M. Hammood Applied Science, University of Arkansas at Little Rock, Little Rock, USA e-mail: [email protected] K. -
The Status of Stream Ciphers After the Estream Project*
The Status of Stream Ciphers after the eSTREAM Project? Bart Preneel COSIC, K.U.Leuven, Belgium abstract 1 The eSTREAM project is a multi-year project within the ECRYPT Net- work of Excellence (http://www.ecrypt.eu.org/stream/). Launched in 2004, it is expected to come to a conclusion in April of 2008 with the publication of a portfolio of promising new stream cipher designs. For many years stream ciphers of a dedicated design were seen as an impor- tant complement to block ciphers. While both stream and block ciphers provide what is termed symmetric encryption, where both the sender and the receiver of a protected message share the same key, they have different characteristics making them suitable for different applications. And while a block cipher could be used as a stream cipher, this was previously viewed as a second-best choice. However the widespread adoption of the AES [1] —a trusted block cipher with excellent performance characteristics—has changed this. For the vast majority of applications one can just use the AES (in an appropriate way) with no need to look for alternatives. That said, there are two situations where a dedicated stream cipher might still hold an advantage: (1) in software applications requiring a very high encryption/decryption rate and (2) in hardware applications where physical resources, e.g. space or power, are severely restricted. Over a three-year period, an initial set of 34 new stream cipher designs— submitted from around the world—has been gradually reduced to 16 finalist ciphers suitable for software or hardware implementation. -
Generic Attacks on Stream Ciphers
Generic Attacks on Stream Ciphers John Mattsson Generic Attacks on Stream Ciphers 2/22 Overview What is a stream cipher? Classification of attacks Different Attacks Exhaustive Key Search Time Memory Tradeoffs Distinguishing Attacks Guess-and-Determine attacks Correlation Attacks Algebraic Attacks Sidechannel Attacks Summary Generic Attacks on Stream Ciphers 3/22 What is a stream cipher? Input: Secret key (k bits) Public IV (v bits). Output: Sequence z1, z2, … (keystream) The state (s bits) can informally be defined as the values of the set of variables that describes the current status of the cipher. For each new state, the cipher outputs some bits and then jumps to the next state where the process is repeated. The ciphertext is a function (usually XOR) of the keysteam and the plaintext. Generic Attacks on Stream Ciphers 4/22 Classification of attacks Assumed that the attacker has knowledge of the cryptographic algorithm but not the key. The aim of the attack Key recovery Prediction Distinguishing The information available to the attacker. Ciphertext-only Known-plaintext Chosen-plaintext Chosen-chipertext Generic Attacks on Stream Ciphers 5/22 Exhaustive Key Search Can be used against any stream cipher. Given a keystream the attacker tries all different keys until the right one is found. If the key is k bits the attacker has to try 2k keys in the worst case and 2k−1 keys on average. An attack with a higher computational complexity than exhaustive key search is not considered an attack at all. Generic Attacks on Stream Ciphers 6/22 Time Memory Tradeoffs (state) Large amounts of precomputed data is used to lower the computational complexity. -
The Rc4 Stream Encryption Algorithm
TTHEHE RC4RC4 SSTREAMTREAM EENCRYPTIONNCRYPTION AALGORITHMLGORITHM William Stallings Stream Cipher Structure.............................................................................................................2 The RC4 Algorithm ...................................................................................................................4 Initialization of S............................................................................................................4 Stream Generation..........................................................................................................5 Strength of RC4 .............................................................................................................6 References..................................................................................................................................6 Copyright 2005 William Stallings The paper describes what is perhaps the popular symmetric stream cipher, RC4. It is used in the two security schemes defined for IEEE 802.11 wireless LANs: Wired Equivalent Privacy (WEP) and Wi-Fi Protected Access (WPA). We begin with an overview of stream cipher structure, and then examine RC4. Stream Cipher Structure A typical stream cipher encrypts plaintext one byte at a time, although a stream cipher may be designed to operate on one bit at a time or on units larger than a byte at a time. Figure 1 is a representative diagram of stream cipher structure. In this structure a key is input to a pseudorandom bit generator that produces a stream -
Stream Cipher Designs: a Review
SCIENCE CHINA Information Sciences March 2020, Vol. 63 131101:1–131101:25 . REVIEW . https://doi.org/10.1007/s11432-018-9929-x Stream cipher designs: a review Lin JIAO1*, Yonglin HAO1 & Dengguo FENG1,2* 1 State Key Laboratory of Cryptology, Beijing 100878, China; 2 State Key Laboratory of Computer Science, Institute of Software, Chinese Academy of Sciences, Beijing 100190, China Received 13 August 2018/Accepted 30 June 2019/Published online 10 February 2020 Abstract Stream cipher is an important branch of symmetric cryptosystems, which takes obvious advan- tages in speed and scale of hardware implementation. It is suitable for using in the cases of massive data transfer or resource constraints, and has always been a hot and central research topic in cryptography. With the rapid development of network and communication technology, cipher algorithms play more and more crucial role in information security. Simultaneously, the application environment of cipher algorithms is in- creasingly complex, which challenges the existing cipher algorithms and calls for novel suitable designs. To accommodate new strict requirements and provide systematic scientific basis for future designs, this paper reviews the development history of stream ciphers, classifies and summarizes the design principles of typical stream ciphers in groups, briefly discusses the advantages and weakness of various stream ciphers in terms of security and implementation. Finally, it tries to foresee the prospective design directions of stream ciphers. Keywords stream cipher, survey, lightweight, authenticated encryption, homomorphic encryption Citation Jiao L, Hao Y L, Feng D G. Stream cipher designs: a review. Sci China Inf Sci, 2020, 63(3): 131101, https://doi.org/10.1007/s11432-018-9929-x 1 Introduction The widely applied e-commerce, e-government, along with the fast developing cloud computing, big data, have triggered high demands in both efficiency and security of information processing. -
Analysis of Chosen Plaintext Attacks on the WAKE Stream Cipher
Analysis of chosen plaintext attacks on the WAKE Stream Cipher Marina Pudovkina [email protected] Moscow Engineering Physics Institute (Technical University) Department of Cryptology and Discrete Mathematics Abstract. Stream ciphers are an important class of encryption algorithms, which are widely used in practice. In this paper the security of the WAKE stream cipher is investigated. We present two chosen plaintext attacks on this cipher. The complexities of these attacks can be estimated as 1019.2 and 1014.4. Keywords. WAKE. Stream Cipher. Cryptanalysis. 1 Introduction Symmetric cryptosystems can be subdivided into block and stream ciphers. Block ciphers operate with a fixed transformation on large blocks of plaintext data; stream ciphers operate with a time- varying transformation on individual plaintext digits. Typically, a stream cipher consists of a keystream generator whose pseudo-random output sequence is added modulo 2 to the plaintext bits. A major goal in stream cipher design is to efficiently produce random-looking sequences. But the keystream can be generated efficiently; there certainly exists such a simple description. WAKE is the Word Auto Key Encryption algorithm, invented by David Wheeler [1]. It has a very simple description and produces a stream of 4n-bit words, which can be XORed with a plaintext stream to produce ciphertext, or XORed with a ciphertext stream to produce plaintext. It is fast on most modern computers, and relies on repeated table use and having a large state space. WAKE works in CFB mode; the previous ciphertext word is used to generate the next key word. It is being used in the current version of Dr. -
6.6 Case Study: A5 Stream Cipher
6.6 Case Study: A5 Stream Cipher A. A5/1 stream cipher key generator for secure GSM conversations Note. A GSM conversation is sent as a sequence of frames per 4.6 millisecond, and each frame contains 228 bits. @G. Gong, 2003 1 Description of the A5/1 K,64-bit key stream cipher: 64-bit key to generate a key stream where each 228- A5 bit used for one frame (228-bit) encryption. 1-bit output 228-bit buffer GSM message: … 228-bit 228-bit Output: 228-bit ciphertext, one 1 frame Bitwise addition frame of cipher @G. Gong, 2003 2 Construction of A5/1 Generator: Parameters: (a) Three LSFRs which generate m-sequences with periods 219 - 1, 222 - 1, 223 - 1, respectively. 1. LFSR 1: 19 5 2 generates a = {a(t)}. f1(x) = x + x + x + x +1 22 2. LFSR 2: f 2 ( x ) = x + x + 1 generates b = {b(t)}. 3. LFSR 3: 23 16 2 generates c = {c(t)}. f3 (x) = x + x + x + x +1 4. Tap positions: d1 = 11, d2 = 12 and d3 = 13. @G. Gong, 2003 3 (b) Majority function f(x1, x2, x3) = (y1, y2, y3) is defined by f (a(t +11),b(t +12),c(t +13)) a(t +11) b(t +12) c(t +13) = (y1, y2, y3) (1,1,1) 0 0 0 1 1 1 (1,1,0) 0 0 1 1 1 0 (0,1,1) 0 1 1 1 0 0 (1,0,1) 1 0 1 0 1 0 Output: The output sequence u = {u(t)} which performs at time t, u(t) = a(i1) + b(i2) + c(i3), t = 0, 1, .. -
Iris Um Oifig Maoine Intleachtúla Na Héireann Journal of the Intellectual Property Office of Ireland
Iris um Oifig Maoine Intleachtúla na hÉireann Journal of the Intellectual Property Office of Ireland Iml. 96 Cill Chainnigh 04 August 2021 Uimh. 2443 CLÁR INNSTE Cuid I Cuid II Paitinní Trádmharcanna Leath Leath Official Notice 2355 Official Notice 1659 Applications for Patents 2354 Applications for Trade Marks 1660 Applications Published 2354 Oppositions under Section 43 1717 Patents Granted 2355 Application(s) Amended 1717 European Patents Granted 2356 Application(s) Withdrawn 1719 Applications Withdrawn, Deemed Withdrawn or Trade Marks Registered 1719 Refused 2567 Trade Marks Renewed 1721 Patents Lapsed 2567 International Registrations under the Madrid Request for Grant of Supplementary Protection Protocol 1724 Certificate 2568 International Trade Marks Protected 1735 Supplementary Protection Certificate Granted 2568 Cancellations effected for the following Patents Expired 2570 goods/services under the Madrid protocol 1736 Dearachtaí Designs Information under the 2001 Act Designs Registered 2578 Designs Renewed 2582 The Journal of the Intellectual Property Office of Ireland is published fortnightly. Each issue is freely available to view or download from our website at www.ipoi.gov.ie © Rialtas na hÉireann, 2021 © Government of Ireland, 2021 2353 (04/08/2021) Journal of the Intellectual Property Office of Ireland (No. 2443) Iris um Oifig Maoine Intleachtúla na hÉireann Journal of the Intellectual Property Office of Ireland Cuid I Paitinní agus Dearachtaí No. 2443 Wednesday, 4 August, 2021 NOTE: The office does not guarantee the accuracy of its publications nor undertake any responsibility for errors or omissions or their consequences. In this Part of the Journal, a reference to a section is to a section of the Patents Act, 1992 unless otherwise stated.