DOCSLIB.ORG

History of Cryptography and Cryptanalysis

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
History of Cryptography and Cryptanalysis History Of Cryptography And Cryptanalysis Aleksandar Nikoli´c University of Novi Sad Faculty of Technical Sciences Chair of Informatics [email protected] April 11, 2013 Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 1 / 32 Overview 1 Introduction 2 History 3 Cryptool 4 Ciphers - making and breaking Caesar’s cipher Simple substitution Vigen`ere Cipher One time pad Enigma machine 5 Conclusion Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 2 / 32 Introduction What is cryptography? Cryptography is the (very) delicate science of keeping secrets secret. In the old days, cryptography’s sole purpose was to ensure secret communication between two parties. This was achieved by enciphering the message thus rendering it unintelligible to anyone but those who know the secret code. Today, cryptography is used virtually everywhere for all sorts of different purposes: authentication, digital signatures, digital currency, secure computation. Few historical ciphers shall be reviewed and their flaws exposed. Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 3 / 32 Introduction Terminology Cryptography The science of keeping secrets secret. Cryptanalysis The art and science of breaking and deciphering secret codes. Cryptology Science, branch of mathematics, that includes both of the above. Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 4 / 32 Introduction Terminology Plaintext Non-enciphered, readable message. Ciphertext Enciphered message, appears to be nonsensical. Encryption Process of turning plaintext into ciphertext. Decryption Reverse. Turning ciphertext into plaintext. Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 5 / 32 Introduction Usual characters Explaining cryptographic schemes and protocols can sometimes be tricky. These are the standard characters everybody uses when trying to explain anything. Alice and Bob - they are trying to communicate securely. Eve - eavesdropper, trying to listen in on Alice and Bob. Malory - malicious person. Tries to actively disrupt, or in some way trick Alice and Bob and break the security of their communication. Charlie - third person that wants to communicate securely. Trent - trusted third party. Alice, Bob and Charlie can rely on him to play fair and keep secrets. ... Some go too far and say that Alice is Bob’s girlfriend, Eve likes Bob, Malory is his ex, Trent is a good buddy and so on. Cryptographers are strange. Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 6 / 32 History Beginnings Since the dawn of written communication, there was a need for its secrecy. First known uses of ciphers date back to ancient Egypt where ciphers were carved in stone. There are stories of old soldiers/pirates/spies that would shave their head, tattoo the message and let the hair grow back. Most ancient ciphers were of two kinds: transposition - rearranging the orders of letters. substitution - changing one letter to another. Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 7 / 32 History First ciphers Atbash - Hebrew cipher was a first example of substitution cipher. first letter substituted with last, second with second to last and so on obviously, if you knew the scheme, you knew to read it, no key Scytale - Greek cipher - first example of transposition cipher. Used cylinders of different sizes. Long piece of paper rolled onto the cylinder, then text is written vertically. Diameter of the cylinder is the key for decipherment Caesar’s Cipher - shifts the alphabet, thus substituting the letters. Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 8 / 32 Cryptool A slight digression - Cryptool Cryptool CrypTool 1 is a free, open-source Windows program for cryptography and cryptanalysis. It is available in 5 languages and the most wide-spreaded e-learning software of its kind. It supports both contemporary teaching methods at schools and universities as well as awareness training for employees and civil servants. We will be using it to demonstrate how different historical ciphers work and how they can be broken. Can be downloaded at: http://www.cryptool.org/en/ download-ct1-en/215-ct1-downloads-eng Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 9 / 32 Ciphers - making and breaking Caesar’s cipher Caesar’s cipher - making Used by Caesar to securely communicate to his generals. Substitution cipher - each letter of the alphabet is shifted a number of position. Caesar supposedly used to shift the alphabet by 3. number of shifts serves as a cipher key Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 10 / 32 Ciphers - making and breaking Caesar’s cipher Caesar’s cipher - making DEMO TIME! Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 11 / 32 Ciphers - making and breaking Caesar’s cipher Caesar’s cipher - breaking limited key space, only 26 different values (for English alphabet) easy to try them all can be done with pen and paper highlights one important fact about ciphers still relevant today Keyspace Key space (number of unique keys) of a cipher must be sufficiently large to render brute force attack unfeasible. Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 12 / 32 Ciphers - making and breaking Simple substitution Simple substitution the flaw of Caesar’s cipher is it’s small key space lets improve on it by, instead of simply shifting the alphabet, rearrange the letters in some way Atbash and Caesar’s ciphers are just examples of this algorithm with specific way of generating the mixed alphabet mixed alphabet can be generated by using a keyword at the beginning and removing the repeating letters ABCDEFGHIJKLMNOPQRSTUVWXYZ QUICKBROWNADEFGHJLMOPSTVYZ some letters can remain the same easy to communicate to the other party or just plain randomly scrambled Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 13 / 32 Ciphers - making and breaking Simple substitution Simple substitution - making DEMO TIME! Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 14 / 32 Ciphers - making and breaking Simple substitution Simple substitution - breaking Any ideas on how to break this? Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 15 / 32 Ciphers - making and breaking Simple substitution Frequency analysis Frequency analysis is a study of frequency of letters in words in a language Letter frequency is not uniform ETAOINSHRDLU are (in that order) the most frequent letters in the regular english text. Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 16 / 32 Ciphers - making and breaking Simple substitution Simple substitution - breaking Weak ciphers obfuscate the characters, but not the frequency Ciphertext needs to be long enough for frequencies to be correct (300+ characters should be enough) Can be concluded that the most frequent character in the ciphertext is actually the letter E Same goes for second most frequent, the third and so on . Bigrams and Trigrams frequencies can also be used Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 17 / 32 Ciphers - making and breaking Vigen`ere Cipher Major flaw in the simple substitution ciphers is that character occurance frequency isn’t obfuscated and can be exploited to reveal the plaintext Blase De Vigenere designed his cipher to overcome this flaw. It was used to be called le chiffre ind´echiffrable Uses a table and a keyword. Table is a 26x26 alphabet matrix If message was ATTACK and keyword was SECRET the ciphertext would be SXVRGD Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 18 / 32 Ciphers - making and breaking Vigen`ere Cipher Vigen`ere CipherSimple substitution - making DEMO TIME! Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 19 / 32 Ciphers - making and breaking Vigen`ere Cipher Vigen`ere Cipher - breaking Surelly this one is secure!?! Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 20 / 32 Ciphers - making and breaking Vigen`ere Cipher Vigen`ere Cipher - breaking What we have is actually just multiple different substitutions. Every other character (up to the length of a keyword) is substituted by another mixed alphabet If we knew what the keyword length was, we can split the ciphertext into multiple simple substitution ciphertexts and solve them as before. Problem with this cipher is the repeating nature of it’s key Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 21 / 32 Ciphers - making and breaking Vigen`ere Cipher Kasiski test Sometimes, repeated words in the plaintext will be encrypted by the same part of the key Key: ABCDABCDABCDABCDABCDABCDABCD Plaintext: CRYPTOISSHORTFORCRYPTOGRAPHY Ciphertext: CSASTPKVSIQUTGQUCSASTPIUAQJB By counting the distance between the repetitions, we can guess the length of the key. In this case, the distance is 16, so the probable key lengths are 2,4,8, or 16. Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 22 / 32 Ciphers - making and breaking Vigen`ere Cipher Index Of Coincidence Another way to determine key length Exploiting the known probabilities of the language, we can estimate the key length with this formula: 25 n (n − 1) κ = X i i . c n(n − 1) i=0 Aleksandar Nikoli´c (FTN) History Of Cryptography April 11, 2013 23 / 32 Ciphers - making and breaking One time pad One time pad Major flaw of the Vigen`ere Cipher is it’s repeating key. What if we made the key as long as the message? One time pad cipher - the key is as long as the message. Provably unbreakable! Aleksandar Nikoli´c (FTN) History
Load more

Recommended publications
  • Words Should Be Fun: Scrabble As a Tool for Language Preservation in Tuvan and Other Local Languages1
    Vol. 4 (2010), pp. 213-230 http://nflrc.hawaii.edu/ldc/ http://hdl.handle.net/10125/4480 Words should be fun: Scrabble as a tool for language preservation in Tuvan and other local languages1 Vitaly Voinov The University of Texas at Arlington One small but practical way of empowering speakers of an endangered language to maintain their language’s vitality amidst a climate of rapid globalization is to introduce a mother-tongue version of the popular word game Scrabble into their society. This paper examines how versions of Scrabble have been developed and used for this purpose in various endangered or non-prestige languages, with a focus on the Tuvan language of south Siberia, for which the author designed a Tuvan version of the game. Playing Scrab- ble in their mother tongue offers several benefits to speakers of an endangered language: it presents a communal approach to group literacy, promotes the use of a standardized orthography, creates new opportunities for intergenerational transmission of the language, expands its domains of usage, and may heighten the language’s external and internal prestige. Besides demonstrating the benefits of Scrabble, the paper also offers practical suggestions concerning both linguistic factors (e.g., choice of letters to be included, cal- culation of letter frequencies, dictionary availability) and non-linguistic factors (board de- sign, manufacturing, legal issues, etc.) relevant to producing Scrabble in other languages for the purpose of revitalization. 1. INTRODUCTION.2 The past several decades have seen globalization penetrating even the most remote corners of the world, bringing with them popular American exports such as Coca-Cola and Hollywood movies.
    [Show full text]
  • Questions These Questions Are in a Specific Order. 1. What Is Scrabble
    Questions Re: The Game of Scrabble Radio Interview - 14th March 2019 - 2AIRFM These questions are in a specific order. 1. What is Scrabble? 2:30 sec. 2. Who invented it? 1:40 sec 3. Why is it called Scrabble? 30 sec 4. Why play Scrabble? 1:30 sec 5. Why should I join a Scrabble Club? 2:30 sec 6. What dictionary should I use? 3:00 mins. 7. Why are there weird words in the Scrabble Dictionary? 3:00 mins 8. What should I know? 2:30 sec 9. What is a good score in Scrabble? 1 min 10. How can I improve my Scrabble score? 1 min 11. How did you get interested in Scrabble? 1 min That’s eleven questions the volume has been turned up to 11! These are some suggestions for songs to be played between breaks:- Words of love – the Beatles G.L.O.R.I.A. - Them featuring Van Morrison Words - the Bee Gees V.A.C.A.T.I.O.N. - Connie Francis Words - Neil Young D.I.V.O.R.C.E. - Tammy Wynette https://soundcloud.com/user147680538/community-interview-14th-march-2019 1. What is Scrabble? The game of Scrabble has been around since 1933 in one form or another in Western society, so I’ve always thought that everyone would have least heard of it. It wasn’t until recently that I realised there are people out there who don’t know what it is. Oddly enough, one of my relatives who is a very worldly character having run various clubs in his day, whom you would have thought was very knowledgeable brought this fact home to me, he was unaware of what it is.
    [Show full text]
  • Consonants, Vowels and Letter Frequency Stephen J
    This article was downloaded by:[Canadian Research Knowledge Network] On: 8 January 2008 Access Details: [subscription number 789349985] Publisher: Psychology Press Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Language and Cognitive Processes Publication details, including instructions for authors and subscription information: http://www.informaworld.com/smpp/title~content=t713683153 Transposed-letter effects: Consonants, vowels and letter frequency Stephen J. Lupker a; Manuel Perea b; Colin J. Davis c a University of Western Ontario, London, ON, Canada b Universitat de València, València, Spain c Royal Holloway University of London, Egham, UK Online Publication Date: 01 January 2008 To cite this Article: Lupker, Stephen J., Perea, Manuel and Davis, Colin J. (2008) 'Transposed-letter effects: Consonants, vowels and letter frequency', Language and Cognitive Processes, 23:1, 93 - 116 To link to this article: DOI: 10.1080/01690960701579714 URL: http://dx.doi.org/10.1080/01690960701579714 PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf This article maybe used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
    [Show full text]
  • Letter Frequency Analysis of Languages Using Latin Alphabet
    International Linguistics Research; Vol. 1, No. 1; 2018 ISSN 2576-2974 E-ISSN 2576-2982 https://doi.org/10.30560/ilr.v1n1p18 Letter Frequency Analysis of Languages Using Latin Alphabet Gintautas Grigas1 & Anita Juškevičienė1 1 Institute of Data Science and Digital Technologies, Vilnius University, Lithuania Correspondence: Anita Juškevičienė, Institute of Data Science and Digital Technologies, Vilnius University, Akademijos str. 4, LT-08663, Vilnius, Lithuania. Tel: 370-5210-9314. E-mail: [email protected], [email protected] Received: February 23, 2018; Accepted: March 8, 2018; Published: March 26, 2018 Abstract The evaluation of the peculiarities of alphabets, particularly the frequency of letters is essential when designing keyboards, analysing texts, designing alphabet-based games, and doing some text mining. Thus, it is important to determine what might be useful for designers of text input tools, and of other technologies related to sets of letters. Knowledge of common features among different languages gives an opportunity to take advantage of the experience of other languages. Nowadays an increasing amount of texts is published on the Internet. In order to adequately compare the frequencies of letters in different languages used in the online space, Wikipedia texts have been selected as a source material for investigation. This paper presents the Method of the Adjacent Letter Frequency Differences in the frequency line, which helps to evaluate frequency breakpoints. This is a uniform evaluation criterion for 25 main languages using Latin script in order to highlight the similarities and differences among them. Research focuses on the letter frequency analysis in the area of rarely used native letters and frequently used foreign letters in a particular language.
    [Show full text]
  • Shift Cipher Substitution Cipher Vigenère Cipher Hill Cipher
    Lecture 2 Classical Cryptosystems Shift cipher Substitution cipher Vigenère cipher Hill cipher 1 Shift Cipher • A Substitution Cipher • The Key Space: – [0 … 25] • Encryption given a key K: – each letter in the plaintext P is replaced with the K’th letter following the corresponding number ( shift right ) • Decryption given K: – shift left • History: K = 3, Caesar’s cipher 2 Shift Cipher • Formally: • Let P=C= K=Z 26 For 0≤K≤25 ek(x) = x+K mod 26 and dk(y) = y-K mod 26 ʚͬ, ͭ ∈ ͔ͦͪ ʛ 3 Shift Cipher: An Example ABCDEFGHIJKLMNOPQRSTUVWXYZ 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 • P = CRYPTOGRAPHYISFUN Note that punctuation is often • K = 11 eliminated • C = NCJAVZRCLASJTDQFY • C → 2; 2+11 mod 26 = 13 → N • R → 17; 17+11 mod 26 = 2 → C • … • N → 13; 13+11 mod 26 = 24 → Y 4 Shift Cipher: Cryptanalysis • Can an attacker find K? – YES: exhaustive search, key space is small (<= 26 possible keys). – Once K is found, very easy to decrypt Exercise 1: decrypt the following ciphertext hphtwwxppelextoytrse Exercise 2: decrypt the following ciphertext jbcrclqrwcrvnbjenbwrwn VERY useful MATLAB functions can be found here: http://www2.math.umd.edu/~lcw/MatlabCode/ 5 General Mono-alphabetical Substitution Cipher • The key space: all possible permutations of Σ = {A, B, C, …, Z} • Encryption, given a key (permutation) π: – each letter X in the plaintext P is replaced with π(X) • Decryption, given a key π: – each letter Y in the ciphertext C is replaced with π-1(Y) • Example ABCDEFGHIJKLMNOPQRSTUVWXYZ πBADCZHWYGOQXSVTRNMSKJI PEFU • BECAUSE AZDBJSZ 6 Strength of the General Substitution Cipher • Exhaustive search is now infeasible – key space size is 26! ≈ 4*10 26 • Dominates the art of secret writing throughout the first millennium A.D.
    [Show full text]
  • An Improved Arabic Keyboard Layout
    Sci.Int.(Lahore),33(1),5-15,2021 ISSN 1013-5316; CODEN: SINTE 8 5 AN IMPROVED ARABIC KEYBOARD LAYOUT 1Amjad Qtaish, 2Jalawi Alshudukhi, 3Badiea Alshaibani, 4Yosef Saleh, 5Salam Bazrawi College of Computer Science and Engineering, University of Ha'il, Ha'il, Saudi Arabia. [email protected], [email protected], [email protected], [email protected], [email protected] ABSTRACT: One of the most important human–machine interaction (HMI) systems is the computer keyboard. The keyboard layout (KL) dictates how a person interacts with a physical keyboard through the way in which the letters, numbers, punctuation marks, and symbols are mapped and arranged on the keyboard. Mapping letters onto the keys of a keyboard is complex because many issues need to be taken into considerations, such as the nature of the language, finger fatigue, hand balance, typing speed, and distance traveled by fingers during typing and finger movements. There are two main kinds of KL: English and Arabic. Although numerous research studies have proposed different layouts for the English keyboard, there is a lack of research studies that focus on the Arabic KL. To address this lack, this study analyzed and clarified the limitations of the standard legacy Arabic KL. Then an efficient Arabic KL was proposed to overcome the limitations of the current KL. The frequency of Arabic letters and bi-gram probabilities were measured on a large Arabic corpus in order to assess the current KL and to design the improved Arabic KL. The improved Arabic KL was then evaluated and compared against the current KL in terms of letter frequency, finger-travel distance, hand and finger balance, bi-gram frequency, row distribution, and most frequent words.
    [Show full text]
  • Cryptology: an Historical Introduction DRAFT
    Cryptology: An Historical Introduction DRAFT Jim Sauerberg February 5, 2013 2 Copyright 2013 All rights reserved Jim Sauerberg Saint Mary's College Contents List of Figures 8 1 Caesar Ciphers 9 1.1 Saint Cyr Slide . 12 1.2 Running Down the Alphabet . 14 1.3 Frequency Analysis . 15 1.4 Linquist's Method . 20 1.5 Summary . 22 1.6 Topics and Techniques . 22 1.7 Exercises . 23 2 Cryptologic Terms 29 3 The Introduction of Numbers 31 3.1 The Remainder Operator . 33 3.2 Modular Arithmetic . 38 3.3 Decimation Ciphers . 40 3.4 Deciphering Decimation Ciphers . 42 3.5 Multiplication vs. Addition . 44 3.6 Koblitz's Kid-RSA and Public Key Codes . 44 3.7 Summary . 48 3.8 Topics and Techniques . 48 3.9 Exercises . 49 4 The Euclidean Algorithm 55 4.1 Linear Ciphers . 55 4.2 GCD's and the Euclidean Algorithm . 56 4.3 Multiplicative Inverses . 59 4.4 Deciphering Decimation and Linear Ciphers . 63 4.5 Breaking Decimation and Linear Ciphers . 65 4.6 Summary . 67 4.7 Topics and Techniques . 67 4.8 Exercises . 68 3 4 CONTENTS 5 Monoalphabetic Ciphers 71 5.1 Keyword Ciphers . 72 5.2 Keyword Mixed Ciphers . 73 5.3 Keyword Transposed Ciphers . 74 5.4 Interrupted Keyword Ciphers . 75 5.5 Frequency Counts and Exhaustion . 76 5.6 Basic Letter Characteristics . 77 5.7 Aristocrats . 78 5.8 Summary . 80 5.9 Topics and Techniques . 81 5.10 Exercises . 81 6 Decrypting Monoalphabetic Ciphers 89 6.1 Letter Interactions . 90 6.2 Decrypting Monoalphabetic Ciphers .
    [Show full text]
  • 1. History of Cryptography Cryptography (From Greek , Hidden
    1. History of cryptography Cryptography (from Greek , hidden, and , writing), is the practice and study of secret writing(or hidden information). Before the modern era, cryptography was concerned solely with message confidentiality (i.e., encryption) — conversion of messages from a comprehensible form into an incomprehensible one and back again at the other end, rendering it unreadable by interceptors or eavesdroppers without secret knowledge (namely the key needed for decryption of that message). History is filled with examples where people tried to keep information secret from adversaries. Kings and generals communicated with their troops using basic cryptographic methods to prevent the enemy from learning sensitive military information. In fact, Julius Caesar reportedly used a simple cipher, which has been named after him. As society has evolved, the need for more sophisticated methods of protecting data has increased. As the word becomes more connected, the demand for information and electronic services is growing, and with the increased demand comes increased dependency on electronic systems. Already the exchange of sensitive information, such as credit card numbers, over the internet is common practice. Protecting data and electronic system is crucial to our way of living. In recent decades, the field has expanded beyond confidentiality concerns to include techniques for message integrity checking, sender/receiver identity authentication, digital signatures, interactive proofs and secure computation, among others. Modern cryptography intersects the disciplines of mathematics, computer science, and engineering. It is necessary to distinct cryptography, crypto analysis and cryptology. Cryptography is a branch of cryptology dealing with the design of system for encryption and decryption intended to ensure confidentiality, integrity and authenticity of message.
    [Show full text]
  • Research in Education
    Letter Name Learning in Early Childhood Literacy Letter naming is a strong predictor (along with phonological awareness) of phonics acquisition and reading fluency (Evans, Bell, Shaw, Moretti, & Page, 2006; National Reading Panel, 2000; Treiman, Weatherston, & Berch, 1994; Stage, Shepard, Davidson, & Browning, 2001). Letter Name Learning is a Constrained Reading Skill. Scope – Finite set of 26 letters (52 with upper and lower case) Learning curve is steep Time period is relatively brief Importance – Centrality to process of becoming a reader Typicality of the process of becoming a reader Range of Influence Limited to the process of developing decoding automaticity Found in the earliest stages of literacy development Letter Name Learning is a Constrained Reading Skill Unequal Learning – Some letter names and sounds are learned more easily, quickly and deeply than others. Result of unequal exposure rates to letter names and sounds. Mastery – Letter name learning is mastered early, quickly and completely. Universality – Letter name learning needs to be learned by all learners. Letter name learning is composed of identical information or learning elements. Letter Name Learning is a Constrained Reading Skill Codependency Previously reported positive correlations between “constrained” early reading skills and later acquisition of “unconstrained” reading skills are not shown to remain stable at later points in reading development or skill acquisition. Letter Name Learning time should be constrained Letter name learning is not the end-all, be-all of early literacy instruction. Copious amounts of instructional time also be allocated for students to build rich networks of world knowledge and word meanings . Six Stances or Guided Principles for Letter Name Learning 1.
    [Show full text]
  • A Rapid Screening and Testing Protocol for Keyboard Layout Speed Comparison
    IEEE TRANSACTIONS ON HUMAN-MACHINE SYSTEMS 1 A Rapid Screening and Testing Protocol for Keyboard Layout Speed Comparison Joonseok Lee, Member, IEEE, Hanggjun Cho, Student Member, IEEE and R I (Bob) McKay*, Senior Member, IEEE Abstract—We propose an efficient, low-overhead methodology an analysis based on this protocol, comparing a personalised for screening key layouts for ultimate typing speed. It is fast, mobile phone keypad layout with a well-known “ABC” layout. and complementary to existing protocols in other ways. For We compare the theoretical improvement in efficiency, based equal overhead, it allows testing over a wider range of users. It is subject to potential biases, but they can be quantified and on a model of typing speed, with the experimental results adjusted. It assumes an existing standard layout which is used as obtained from our protocol. We conclude with a discussion a comparator. It eliminates bias from differing familiarity and of the assumptions and limitations of the approach, of the finger memory by appropriately mapping both layouts. ways it may be effectively combined with other techniques, We illustrate it with two mobile phone keypad layouts: Sam- and some possible future extensions. sung’s variant of the common ABC layout, and a new user-specific layout (PM). We repeat a comparison previously undertaken by a training-based method, which used 10 participants, and II. BACKGROUND estimated a 54% speedup for PM (SD=35%). The new method A. Earlier Methodologies used 116 participants and estimated a 19.5% speedup (SD=7.5%). Differences in speedup estimates can be explained by the wide There are obstacles to fair, rapid layout comparison.
    [Show full text]
  • Xerox University Microfilms GUDES, Ehud, 1945- the APPLICATION of CRYPTOGRAPHY to DATA BASE SECURITY
    INFORMATION TO USERS This material was produced from a microfilm copy of the original document. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the original submitted. The following explanation of techniques is provided to help you understand markings or patterns which may appear on this reproduction. 1. The sign or "target" for pages apparently lacking from the document photographed is "Missing Page(s)". If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting thru an image and duplicating adjacent pages to insure you complete continuity. 2. When an image on the film is obliterated with a large round black mark, it is an indication that the photographer suspected that the copy may have moved during exposure and thus cause a blurred image. You will find a good image of the page in the adjacent frame. 3. When a map, drawing or chart, etc., was part of the material being photographed the photographer followed a definite method in "sectioning" the material. It is customary to begin photoing at the upper left hand corner of a large sheet and to continue photoing from left to right in equal sections with a small overlap. If necessary, sectioning is continued again — beginning below the first row and continuing on until complete. 4. The majority of users indicate that the textual content is of greatest value, however, a somewhat higher quality reproduction could be made from "photographs" if essential to the understanding of the dissertation.
    [Show full text]
  • Evolution of Encryption Techniques and Data Security Mechanisms
    World Applied Sciences Journal 33 (10): 1597-1613, 2015 ISSN 1818-4952 © IDOSI Publications, 2015 DOI: 10.5829/idosi.wasj.2015.33.10.286 Evolution of Encryption Techniques and Data Security Mechanisms 12K. John Singh and R. Manimegalai 1School of Information Technology and Engineering, VIT University Vellore, Tamil Nadu, India 2Department of Computer Science and Engineering, Park College of Engineering and Technology, Coimbatore, Tamil Nadu, India Abstract: Rapid advancements in information technology world resulted in the drastic growth in the amount of data transferred through the network. Networks used for multimedia communication do not provide much security for data transfer as well as digital communication. Billions of people use internet options for essential communication and as a tool for commercial interests. Therefore, security is an enormously important issue to deal with. As web services also have data storage and data communication, we need to protect and provide confidentiality. There is a need to recognize the different aspects of security and their applications. This paper provides a comprehensive overview of evolution of encryption algorithms right from ancient cryptography techniques to modern encryption algorithms. Key words: Confidentiality Authentication Substitution Cipher Enigma Rotor Hash Function INTRODUCTION security. More generally, cryptography is the science of privacy and is an ancient art. It is about constructing Before taking a deep dive into the ocean of and analysing the protocols that overcomes the authority cryptography. The cryptosystem or a cipher system of adversary and which are correlated with various conceals information from unintentional user [1]. aspects of information security such as data integrity, Cryptography is the science of creating that kind of non-repudiation and confidentiality and authentication cryptosystem where as cryptanalysis is the scientific art [2].
    [Show full text]