Elastic Block Ciphers: the Basic Design
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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. -
Mcoe: a Family of Almost Foolproof On-Line Authenticated Encryption Schemes
McOE: A Family of Almost Foolproof On-Line Authenticated Encryption Schemes Ewan Fleischmann Christian Forler Stefan Lucks Bauhaus-Universit¨atWeimar FSE 2012 Fleischmann, Forler, Lucks. FSE 2012. McOE: A Family . {1{ Overview Fleischmann, Forler, Lucks. FSE 2012. McOE: A Family . {2{ 1. Motivation I Goldwasser and Micali (1984): requirement: given 2 ciphertexts, adversary cannot even detect when the same plaintext has been encrypted twice consequence: encryption stateful or probabilitistic (or both) I Rogaway (FSE 2004): formalizes state/randomness by nonces Plaintext Header Key Nonce 01 02 03 ... Ciphertext Authentication Tag Fleischmann, Forler, Lucks. FSE 2012. McOE: A Family . {3{ Authenticated Encryption I first studied by Katz and Young (FSE 2000) and Bellare and Namprempre (Asiacrypt 2000) I since then many proposed schemes, I nonce based, Plaintext Header Key Nonce I and proven secure assuming a \nonce-respecting01 02 03 ... adversary" I any implementation allowing a nonce reuse is not our problem . but maybe it shouldCiphertext Authentication Tag Fleischmann, Forler, Lucks. FSE 2012. McOE: A Family . {4{ Nonce Reuse in Practice I IEEE 802.11 [Borisov, Goldberg, Wagner 2001] I PS3 [Hotz 2010] I WinZip Encryption [Kohno 2004] I RC4 in MS Word and Excel [Wu 2005] I ... application programmer other issues: mistakes: I restoring a file from a backup I cloning the virtual machine the application runs on I ... Fleischmann, Forler, Lucks. FSE 2012. McOE: A Family . {5{ Nonce Reuse { what to Expect? our reasonable (?) expectations I some plaintext information leaks: I identical plaintexts I common prefixes I ect. I but not too much damage: 1. authentication not affected 2. -
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. -
Block Ciphers II
Block Ciphers II Martin Stanek Department of Computer Science Comenius University [email protected] Cryptology 1 (2021/22) Block Ciphers 1 / 26 , Content Confidentiality modes – ECB, CBC, OFB, CFB, CTR Padding Padding oracle attack Ciphertext stealing Authenticated encryption – CCM, GCM Other constructions Format-preserving encryption Encryption of block devices Theoretical security of block ciphers Block Ciphers 2 / 26 , Modes of operation I plaintext usually much longer than the block length I modes of operation can provide: I confidentiality (and not authenticity) ...“traditional” modes I authenticity (and not confidentiality) I confidentiality & authenticity (authenticated encryption) I confidentiality for block-oriented storage devices (e.g. disks) I key wrapping I format-preserving encryption, ... I varying requirements (speed, security properties, ability to parallelize, availability of RNG, etc.) ) different modes Block Ciphers 3 / 26 , Confidentiality modes I the most important confidentiality modes: ECB, CBC, OFB, CFB, CTR I e.g. see NIST SP 800-38A: Recommendation for Block Cipher Modes of Operation: Methods and Techniques I None of these modes provide protection against accidental or adversarial modifications of ciphertext! I however, the effect of ciphertext modification on resulting plaintext varies among modes Block Ciphers 4 / 26 , ECB (Electronic Codebook) P1 P2 P1 P2 Ek Ek Dk Dk C1 C2 C1 C2 encrypt: Ci = Ek (Pi) decrypt: Pi = Dk (Ci) I the simplest mode I data leaks: Ci = Cj , Pi = Pj I easy to rearrange the ciphertexts blocks (permute, duplicate, ...) I encryption and decryption trivially parallelizable I easy to perform a seek (random access) I bit changes do not propagate (single block affected) Block Ciphers 5 / 26 , CBC (Cipher Block Chaining) 1 P1 P2 P1 P2 IV IV (C0) (C0) Ek Ek Dk Dk C1 C2 C1 C2 encrypt: Ci = Ek (Pi Ci 1) decrypt: Pi = Dk (Ci) Ci 1 ⊕ − ⊕ − I IV (initialization vector) – secrecy not required, usually appended as C0 I popular mode (e.g. -
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. -
The Security of Ciphertext Stealing
The Security of Ciphertext Stealing Phillip Rogaway1, Mark Wooding2, and Haibin Zhang1 1 Dept. of Computer Science, University of California, Davis, USA 2 Thales e-Security Ltd, UK Abstract. We prove the security of CBC encryption with ciphertext stealing. Our results cover all versions of ciphertext stealing recently recommended by NIST. The complexity assumption is that the under- lying blockcipher is a good PRP, and the security notion achieved is the strongest one commonly considered for chosen-plaintext attacks, indis- tinguishability from random bits (ind$-security). We go on to generalize these results to show that, when intermediate outputs are slightly de- layed, one achieves ind$-security in the sense of an online encryption scheme, a notion we formalize that focuses on what is delivered across an online API, generalizing prior notions of blockwise-adaptive attacks. Finally, we pair our positive results with the observation that the ver- sion of ciphertext stealing described in Meyer and Matyas’s well-known book (1982) is not secure. Keywords: blockwise-adaptive attacks, CBC, ciphertext stealing, cryp- tographic standards, modes of operation, provable security. 1 Introduction Ciphertext stealing. Many blockcipher modes require the input be a se- quence of complete blocks, each having a number of bits that is the blockcipher’s blocksize. One approach for dealing with inputs not of this form is ciphertext stealing. The classical combination is CBC encryption and ciphertext stealing, a mode going back to at least 1982 [14]. In 2010, NIST put out an addendum [8] to Special Publication 800-38A [7], the document that had defined blockcipher modes ECB, CBC, CFB, OFB, and CTR. -
Design and Analysis of Lightweight Block Ciphers : a Focus on the Linear
Design and Analysis of Lightweight Block Ciphers: A Focus on the Linear Layer Christof Beierle Doctoral Dissertation Faculty of Mathematics Ruhr-Universit¨atBochum December 2017 Design and Analysis of Lightweight Block Ciphers: A Focus on the Linear Layer vorgelegt von Christof Beierle Dissertation zur Erlangung des Doktorgrades der Naturwissenschaften an der Fakult¨atf¨urMathematik der Ruhr-Universit¨atBochum Dezember 2017 First reviewer: Prof. Dr. Gregor Leander Second reviewer: Prof. Dr. Alexander May Date of oral examination: February 9, 2018 Abstract Lots of cryptographic schemes are based on block ciphers. Formally, a block cipher can be defined as a family of permutations on a finite binary vector space. A majority of modern constructions is based on the alternation of a nonlinear and a linear operation. The scope of this work is to study the linear operation with regard to optimized efficiency and necessary security requirements. Our main topics are • the problem of efficiently implementing multiplication with fixed elements in finite fields of characteristic two. • a method for finding optimal alternatives for the ShiftRows operation in AES-like ciphers. • the tweakable block ciphers Skinny and Mantis. • the effect of the choice of the linear operation and the round constants with regard to the resistance against invariant attacks. • the derivation of a security argument for the block cipher Simon that does not rely on computer-aided methods. Zusammenfassung Viele kryptographische Verfahren basieren auf Blockchiffren. Formal kann eine Blockchiffre als eine Familie von Permutationen auf einem endlichen bin¨arenVek- torraum definiert werden. Eine Vielzahl moderner Konstruktionen basiert auf der wechselseitigen Anwendung von nicht-linearen und linearen Abbildungen. -
Encryption Block Cipher
10/29/2007 Encryption Encryption Block Cipher Dr.Talal Alkharobi 2 Block Cipher A symmetric key cipher which operates on fixed-length groups of bits, termed blocks, with an unvarying transformation. When encrypting, a block cipher take n-bit block of plaintext as input, and output a corresponding n-bit block of ciphertext. The exact transformation is controlled using a secret key. Decryption is similar: the decryption algorithm takes n-bit block of ciphertext together with the secret key, and yields the original n-bit block of plaintext. Mode of operation is used to encrypt messages longer than the block size. 1 Dr.Talal Alkharobi 10/29/2007 Encryption 3 Encryption 4 Decryption 2 Dr.Talal Alkharobi 10/29/2007 Encryption 5 Block Cipher Consists of two algorithms, encryption, E, and decryption, D. Both require two inputs: n-bits block of data and key of size k bits, The output is an n-bit block. Decryption is the inverse function of encryption: D(E(B,K),K) = B For each key K, E is a permutation over the set of input blocks. n Each key K selects one permutation from the possible set of 2 !. 6 Block Cipher The block size, n, is typically 64 or 128 bits, although some ciphers have a variable block size. 64 bits was the most common length until the mid-1990s, when new designs began to switch to 128-bit. Padding scheme is used to allow plaintexts of arbitrary lengths to be encrypted. Typical key sizes (k) include 40, 56, 64, 80, 128, 192 and 256 bits. -
Data Security
Block ciphers BMEVITMAV52 Information and Network Security [email protected] History of cryptography Modern cryptography • Beginning with 1949 – Claude Shannon: Communication Theory of Secrecy Systems • Solid theoretical basis for cryptography and for cryptanalysis – No more alphabets, but ‘bits’ and ‘bytes’ • 1975 DES – Data Encryption Standard • 1976 Diffie-Hellman key exchange • 1977 RSA 2019/20-1 Information and Network Security 2 Block ciphers • Definition – Function that transfers n-bit plaintext block to n-bit ciphertext block (n is the blocklength) – The function is parameterized by a k-bit key – One-to-one mapping (invertible) • Symmetric key block ciphers – E(P,K)=C, D(C,K)=P • Asymmetric key block ciphers – E(P,K1)=C, D(C,K2)=P 2019/20-1 Information and Network Security 3 Well known symmetric block ciphers • 1976: USA standard cipher: DES (Data Encryption Standard) – 64 bit block length, 56 bit key length – As of today it is insecure and slow • 3DES: 3x DES cipher in a row – 2x not enough, 2 keys are already enough – 64 bit block length, 112 bit key length – Satisfactory security, but slow • 2001: AES, the new cipher standard (Advanced Encryption Standard) – 128 bit block length, 128-192-256 bit key length – State of the art security and speed • Other, less known ciphers – IDEA, Twofish, Blowfish, RC5 2019/20-1 Information and Network Security 4 Requirements to modern ciphers • Avalanche effect – Changing one bit in the input changes half of the output bits • Completeness – Each ciphertext bit is a complex function of -
An Efficient VHDL Description and Hardware Implementation of The
An Efficient VHDL Description and Hardware Implementation of the Triple DES Algorithm A thesis submitted to the Graduate School of the University of Cincinnati In partial fulfillment of the requirements for the degree of Master of Science In the Department of Electrical and Computer Engineering Of the College of Engineering and Applied Sciences June 2014 By Lathika SriDatha Namburi B.Tech, Electronics and Communications Engineering, Jawaharlal Nehru Technological University, Hyderabad, India, 2011 Thesis Advisor and Committee Chair: Dr. Carla Purdy ABSTRACT Data transfer is becoming more and more essential these days with applications ranging from everyday social networking to important banking transactions. The data that is being sent or received shouldn’t be in its original form but must be coded to avoid the risk of eavesdropping. A number of algorithms to encrypt and decrypt the data are available depending on the level of security to be achieved. Many of these algorithms require special hardware which makes them expensive for applications which require a low to medium level of data security. FPGAs are a cost effective way to implement such algorithms. We briefly survey several encryption/decryption algorithms and then focus on one of these, the Triple DES. This algorithm is currently used in the electronic payment industry as well as in applications such as Microsoft OneNote, Microsoft Outlook and Microsoft system center configuration manager to password protect user content and data. We implement the algorithm in a Hardware Description Language, specifically VHDL and deploy it on an Altera DE1 board which uses a NIOS II soft core processor. The algorithm takes input encoded using a software based Huffman encoding to reduce its redundancy and compress the data. -
SKINNY-AEAD and SKINNY-Hash Specification
SKINNY-AEAD and SKINNY-Hash v1.1 Christof Beierle1;4, J´er´emy Jean2, Stefan K¨olbl3, Gregor Leander4, Amir Moradi4, Thomas Peyrin5, Yu Sasaki6, Pascal Sasdrich4;7, and Siang Meng Sim5 1 SnT, University of Luxembourg, Luxembourg [email protected] 2 ANSSI, Paris, France [email protected] 3 Cybercrypt A/S, Denmark [email protected] 4 Horst G¨ortzInstitute for IT Security, Ruhr-Universit¨atBochum, Germany [email protected] 5 School of Physical and Mathematical Sciences Nanyang Technological University, Singapore [email protected], [email protected] 6 NTT Secure Platform Laboratories, Japan [email protected] 7 Rambus Cryptography, The Netherlands Table of Contents 1 Introduction...........................................................3 2 Specification..........................................................5 2.1 Notations........................................................5 2.2 Parameter Sets....................................................5 2.3 The Tweakable Block Ciphers SKINNY-128-256 and SKINNY-128-384 ....6 2.4 The AEAD Scheme SKINNY-AEAD....................................9 2.5 The Hash Functionality SKINNY-Hash ................................ 26 3 Security Claims........................................................ 29 4 Design Rationale....................................................... 31 4.1 Rationale for the Tweakable Block Ciphers........................... 31 4.2 Rationale for the AEAD scheme..................................... 33 4.3 Rationale for the Hash Function Scheme............................ -
On the Construction of Variable-Input-Length Ciphers
On the Construction of Variable-Input-Length Ciphers Mihir Bellare1 and Phillip Rogaway2 1 Dept. of Computer Science & Engineering, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093 USA [email protected] www-cse.ucsd.edu/users/mihir/ 2 Dept. of Computer Science, Eng. II Bldg., One Shields Ave., University of California at Davis, Davis, CA 95616 USA [email protected] www.cs.ucdavis.edu/˜rogaway/ Abstract. Whereas a block cipher enciphers messages of some one par- ticular length (the blocklength), a variable-input-length cipher takes mes- sages of varying (and preferably arbitrary) lengths. Still, the length of the ciphertext must equal the length of the plaintext. This paper intro- duces the problem of constructing such objects, and provides a prac- tical solution. Our VIL mode of operation makes a variable-input-length cipher from any block cipher. The method is demonstrably secure in the provable-security sense of modern cryptography: we give a quantita- tive security analysis relating the difficulty of breaking the constructed (variable-input-length) cipher to the difficulty of breaking the underlying block cipher. Keywords: Ciphers, Modes of Operation, Provable Security, Symmetric Encryption. 1 Introduction This paper introduces the question of how to construct ciphers which operate on messages of varying lengths. Such a cipher, F , maps a key K and a plaintext M in 0; 1 (or M in some other set containing strings of various lengths) into f g a ciphertext C = FK (M) having the same length as M. Note that the length of M is not restricted to some xed blocklength n, or even to some multiple of a blocklength.