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Vigenère Cipher Cryptanalysis
Spring 2015 Chris Christensen MAT/CSC 483 Cryptanalysis of the Vigenère Cipher: Kasiski Test The keyword of a Vigenère cipher describes the rotation among the Caesar cipher alphabets that are used. That rotation leads to patterns that can be exploited by a cryptanalyst. If we know the length of the keyword, we can often determine the keyword and, hence, decrypt all messages encrypted with that keyword. Here is a ciphertext message that has been encrypted with a Vigenère cipher. nifon aicum niswt luvet vxshk nissx wsstb husle chsnv ytsro cdsoy nisgx lnona chvch gnonw yndlh sfrnh npblr yowgf unoca cossu ouoll iuvef issoe xgosa cpbew uormh lftaf cmwak bbbdv cqvek muvil qbgnh ntiri ljgig atwnv yuvev iorim cpbsb hxviv buvet vxshk uorim mjbdb pjrut fbueg ntgof yuwmx miodm ipdek uuswx lfjek sewfy yssnm zscmm bpgeb huvez ysaag usaew mffvb wfgim qpilw bbjeu yfbef vbfrt mtwnz uorig wpbvx hjsnm zpfag uhsnm npglb jbqrh mttrh huwek mpfak ljjen hbbnh ooqew vzdak udvum yucbx yoquf vffew vzonx hjumt lfgef vmwnz uxsiz bumag xbbtb kvotx xumpx qswtx l Assume that, somehow, we have discovered that the keyword has length five (which is conveniently the same as the size of the blocks). Then the first letter of each block is encrypted with the same row of the Vigenère square – they are encrypted with the same Caesar cipher. Similarly, the second letter of each block is encrypted with the same row – the same Caesar cipher. The third letters with the same Caesar cipher. The fourth letters with the same Caesar cipher. And, the fifth letters with the same Caesar cipher. -
Elementary Cryptanalysis Classification of Cryptanalytic Attacks
12 Elementary Cryptography Elementary Cryptanalysis The most direct attack on a cryptosystem is an exhaustive key search attack. The key size therefore provides a lower bound on the security of a cryptosystem. As an example we compare the key sizes of several of the cryptosystems we have introduced so far. We assume that the alphabet for each is the 26 character alphabet. Substitution ciphers: Simple substitution ciphers: 26! Affine substitution ciphers: ϕ(26) · 26 = 12 · 26 = 312 Translation substitution ciphers: 26 Transposition ciphers: Transposition ciphers (of block length m): m! Enigma : Rotor choices (3 of 5): 60 Rotor positions: 263 = 17576 Plugboard settings: 105578918576 Total combinations: 111339304373506560 The size of the keyspace is a naive measure, but provides an upper bound on the security of a cryptosystem. This measure ignores any structure, like character frequencies, which might remain intact following encryption. Classification of Cryptanalytic Attacks We do not consider enumeration of all keys a valid cryptanalytic attack, since no well- designed cryptosystem is susceptible to such an approach. The types of legitimate attacks which we consider can be classified in three categories. 1. Ciphertext-only Attack. 2. Known Plaintext Attack. 3. Chosen Plainext Attack. Ciphertext-only Attack. The cryptanalyst intercepts one or more messages all encoded with the same encryption algorithm. Goal: Recover the original plaintext or plaintexts, to discover the deciphering key or find an algorithm for deciphering subsequent messages enciphered with the same key. Known Plaintext Attack. The cryptanalyst has access to not only the ciphertext, but also the plaintext for one or more of the messages. Goal: Recover the deciphering key or find an algorithm for deciphering subsequent mes- sages (or the remaining plaintext) enciphered which use the same key. -
The Mathemathics of Secrets.Pdf
THE MATHEMATICS OF SECRETS THE MATHEMATICS OF SECRETS CRYPTOGRAPHY FROM CAESAR CIPHERS TO DIGITAL ENCRYPTION JOSHUA HOLDEN PRINCETON UNIVERSITY PRESS PRINCETON AND OXFORD Copyright c 2017 by Princeton University Press Published by Princeton University Press, 41 William Street, Princeton, New Jersey 08540 In the United Kingdom: Princeton University Press, 6 Oxford Street, Woodstock, Oxfordshire OX20 1TR press.princeton.edu Jacket image courtesy of Shutterstock; design by Lorraine Betz Doneker All Rights Reserved Library of Congress Cataloging-in-Publication Data Names: Holden, Joshua, 1970– author. Title: The mathematics of secrets : cryptography from Caesar ciphers to digital encryption / Joshua Holden. Description: Princeton : Princeton University Press, [2017] | Includes bibliographical references and index. Identifiers: LCCN 2016014840 | ISBN 9780691141756 (hardcover : alk. paper) Subjects: LCSH: Cryptography—Mathematics. | Ciphers. | Computer security. Classification: LCC Z103 .H664 2017 | DDC 005.8/2—dc23 LC record available at https://lccn.loc.gov/2016014840 British Library Cataloging-in-Publication Data is available This book has been composed in Linux Libertine Printed on acid-free paper. ∞ Printed in the United States of America 13579108642 To Lana and Richard for their love and support CONTENTS Preface xi Acknowledgments xiii Introduction to Ciphers and Substitution 1 1.1 Alice and Bob and Carl and Julius: Terminology and Caesar Cipher 1 1.2 The Key to the Matter: Generalizing the Caesar Cipher 4 1.3 Multiplicative Ciphers 6 -
Ky-57 Vinson
KY-57 VINSON Homepage Crypto KY-57 (VINSON) Index Voice encryption unit Enigma The KY-57 was a wide-band voice encryption unit that was developed in the USA during the 1970s as a replacement of the NESTOR cryptographic products, such as the KY-38. It was suitable for use with a Hagelin wide range of military radios and telehone lines. As part of the VINSON family of devices, it was the main Fialka crypto 'workhorse' of the US Army during the 1980s. Even today, many radios and voice encryption devices are still backwards compatible with the KY-57, that is also known as the TSEC/KY-57. The Siemens airborne version of the KY-57 is called the KY-58. Philips The KY-57 uses the NSA-developed Type-1 KY-57 voice encryption unit Nema SAVILLE cryptographic algorithm. When used in combination with a radio transceiver, such as the Racal SINCGARS non-ICOM RT-1439/VRC, the KY-57 STK allows signal fades or losses for up to 12 seconds without losing synchronization. Transvertex The KY-57 was eventually superceeded by the KY- Gretag 99 that offered newer - more advanced - Telsy cryptographic algorithms, but that was still backwards compatible with the KY-57. Later Tadiran SINCGARS ICOM radios, such as the RT-1523, had built-in KY-57 (VINSON) compatibility. USA USSR Both voice and data can be encrypted with the KY-57. Voice data is digitized using Continuous Variable Slope Delta modulation (CVSD), similar to other voice crypto systems of the same era, such as the UK Philips Spendex-10 , the Spendex 50 and the Telsy TS-500. -
The the Enigma Enigma Machinemachine
TheThe EnigmaEnigma MachineMachine History of Computing December 6, 2006 Mike Koss Invention of Enigma ! Invented by Arthur Scherbius, 1918 ! Adopted by German Navy, 1926 ! Modified military version, 1930 ! Two Additional rotors added, 1938 How Enigma Works Scrambling Letters ! Each letter on the keyboard is connected to a lamp letter that depends on the wiring and position of the rotors in the machine. ! Right rotor turns before each letter. How to Use an Enigma ! Daily Setup – Secret settings distributed in code books. ! Encoding/Decoding a Message Setup: Select (3) Rotors ! We’ll use I-II-III Setup: Rotor Ring Settings ! We’ll use A-A-A (or 1-1-1). Rotor Construction Setup: Plugboard Settings ! We won’t use any for our example (6 to 10 plugs were typical). Setup: Initial Rotor Position ! We’ll use “M-I-T” (or 13-9-20). Encoding: Pick a “Message Key” ! Select a 3-letter key (or indicator) “at random” (left to the operator) for this message only. ! Say, I choose “M-C-K” (or 13-3-11 if wheels are printed with numbers rather than letters). Encoding: Transmit the Indicator ! Germans would transmit the indicator by encoding it using the initial (daily) rotor position…and they sent it TWICE to make sure it was received properly. ! E.g., I would begin my message with “MCK MCK”. ! Encoded with the daily setting, this becomes: “NWD SHE”. Encoding: Reset Rotors ! Now set our rotors do our chosen message key “M-C-K” (13-3-11). ! Type body of message: “ENIGMA REVEALED” encodes to “QMJIDO MZWZJFJR”. -
A History of U.S. Communications Security (U)
A HISTORY OF U.S. COMMUNICATIONS SECURITY (U) THE DAVID G. BOAK LECTURES VOLUME II NATIONAL SECURITY AGENCY FORT GEORGE G. MEADE, MARYLAND 20755 The information contained in this publication will not be disclosed to foreign nationals or their representatives without express approval of the DIRECTOR, NATIONAL SECURITY AGENCY. Approval shall refer specifically to this publication or to specific information contained herein. JULY 1981 CLASSIFIED BY NSA/CSSM 123-2 REVIEW ON 1 JULY 2001 NOT RELEASABLE TO FOREI6N NATIONALS SECRET HA~mLE YIA COMINT CIIA~HJELS O~JLY ORIGINAL (Reverse Blank) ---------- • UNCLASSIFIED • TABLE OF CONTENTS SUBJECT PAGE NO INTRODUCTION _______ - ____ - __ -- ___ -- __ -- ___ -- __ -- ___ -- __ -- __ --- __ - - _ _ _ _ _ _ _ _ _ _ _ _ iii • POSTSCRIPT ON SURPRISE _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ I OPSEC--------------------------------------------------------------------------- 3 ORGANIZATIONAL DYNAMICS ___ -------- --- ___ ---- _______________ ---- _ --- _ ----- _ 7 THREAT IN ASCENDANCY _________________________________ - ___ - - _ -- - _ _ _ _ _ _ _ _ _ _ _ _ 9 • LPI _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ I I SARK-SOME CAUTIONARY HISTORY __ --- _____________ ---- ________ --- ____ ----- _ _ 13 THE CRYPTO-IGNITION KEY __________ --- __ -- _________ - ---- ___ -- ___ - ____ - __ -- _ _ _ 15 • PCSM _ _ _ _ _ _ _ _ _ _ _ _ _ _ -
A Hybrid Cryptosystem Based on Vigenère Cipher and Columnar Transposition Cipher
International Journal of Advanced Technology & Engineering Research (IJATER) www.ijater.com A HYBRID CRYPTOSYSTEM BASED ON VIGENÈRE CIPHER AND COLUMNAR TRANSPOSITION CIPHER Quist-Aphetsi Kester, MIEEE, Lecturer Faculty of Informatics, Ghana Technology University College, PMB 100 Accra North, Ghana Phone Contact +233 209822141 Email: [email protected] / [email protected] graphy that use the same cryptographic keys for both en- Abstract cryption of plaintext and decryption of cipher text. The keys may be identical or there may be a simple transformation to Privacy is one of the key issues addressed by information go between the two keys. The keys, in practice, represent a Security. Through cryptographic encryption methods, one shared secret between two or more parties that can be used can prevent a third party from understanding transmitted raw to maintain a private information link [5]. This requirement data over unsecured channel during signal transmission. The that both parties have access to the secret key is one of the cryptographic methods for enhancing the security of digital main drawbacks of symmetric key encryption, in compari- contents have gained high significance in the current era. son to public-key encryption. Typical examples symmetric Breach of security and misuse of confidential information algorithms are Advanced Encryption Standard (AES), Blow- that has been intercepted by unauthorized parties are key fish, Tripple Data Encryption Standard (3DES) and Serpent problems that information security tries to solve. [6]. This paper sets out to contribute to the general body of Asymmetric or Public key encryption on the other hand is an knowledge in the area of classical cryptography by develop- encryption method where a message encrypted with a reci- ing a new hybrid way of encryption of plaintext. -
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. -
Practical Aspects of Modern Cryptography
University of Washington CSEP 590TU – Practical Aspects of Modern Cryptography Instructors: Josh Benaloh, Brian LaMacchia, John Manferdelli Tuesdays: 6:30-9:30, Allen Center 305 Webpage: http://www.cs.washington.edu/education/courses/csep590/06wi/ Recommended texts: Stinson, Cryptography, Theory and Practice. 2nd Edition, CRC Press, 2002. Menezes, vanOrtshot, Vanstone. Handbook of Applied Cryptography. Ferguson and Schneier, Practical Cryptography. JLM 20060107 22:16 1 New Lecture Schedule Date Topic Lecturer 1 1/3 Practical Aspects of Cryptography Josh 2 1/10 Symmetric Key Ciphers and Hashes John 3 1/17 Public Key Ciphers Josh 4 1/24 Cryptographic Protocols I Brian 5 1/31 Cryptographic Protocols II Brian 6 2/7 Security of Block Ciphers John 7 2/14 AES and Cryptographic Hashes John 8 2/21 Trust, PKI, Key Management [Last HW Brian Assignment) 9 3/1 Random Numbers/Elliptic Curve Crypto Josh 10 3/8 Three topics: Elections, ITAR/Politics, Side All Channels/Timing Attacks, DRM, BigNum Implementation JLM 20060107 22:16 2 Symmetric Key Cryptography and Cryptographic Hashes - I John Manferdelli [email protected] [email protected] Portions © 2004-2005, John Manferdelli. This material is provided without warranty of any kind including, without limitation, warranty of non-infringement or suitability for any purpose. This material is not guaranteed to be error free and is intended for instructional use only. JLM 20060107 22:16 3 Communications Engineers Coat of Arms The Source Sender: Alice Noisy insecure channel Plaintext Compress Encrypt Encode (P) (to save space) (for confidentiality) (to correct errors) The Sink Receiver:Bob Noisy insecure channel Decode Decrypt Decompress Plaintext (for confidentiality) (to correct errors) (to save space) (P) JLM 20060107 22:16 4 Symmetric Encryption Plaintext (P) Encrypt Ciphertext (C) E (P) Key (k) k Ciphertext (C) Decrypt Plaintext (P) D (P) Key (k) k • Symmetric Key cryptographic algorithms use a secret known to the authorized parties called a “key”. -
Introduction
CS 127: Cryptography / Boaz Barak Lecture 1 - Introduction Optional additional reading: Chapters 1 and 2 of Katz-Lindell book.1 Ever since people started to communicate, there were some messages that they wanted kept secret. Thus cryptography has an old though arguably undistin- guished history. For a long time cryptography shared similar features with Alchemy as a domain in which many otherwise smart people would be drawn into making fatal mistakes. d The definitive text on the history of cryptography is David Kahn’s “The Codebreakers”, whose title already hints at the ultimate fate of most cryptosystems.2 (See also “The Code Book” by Simon Singh.) We now recount just a few stories to get a feel for this field. But, before we do so, we should introduce the cast of characters. The basic setting of “encryption” or “secret writing” is the following: one person, whom we will call Alice, wishes to send another person, whom we will call Bob, a secret message. Since Alice and Bob are not in the same room (perhaps because Alice is imprisoned in a castle by her cousin the queen of England), they cannot communicate directly and need to send their message in writing. Alas, there is a third person, whom we will call Eve, that can see their message. Therefore Alice needs to find a way to encode or encrypt the message so that only Bob (and not Eve) will be able to understand it. In 1587, Mary the queen of Scots, and the heir to the throne of England, wanted to arrange the assasination of her cousin, queen Elisabeth I of England, so that she could ascend to the throne and finally escape the house arrest under which she has been for the last 18 years. -
Cryptography
Cryptography Cryptography, or cryptology (from Ancient Greek: κρυπτός, romanized: kryptós "hidden, secret"; and γράφειν graphein, "to write", or -λογία -logia, "study", respectively[1]), is the practice and study of techniques for secure communication in the presence of third parties called adversaries.[2] More generally, cryptography is about constructing and analyzing protocols that prevent third parties or the public from reading private messages;[3] various aspects in information security such as data confidentiality, data integrity, authentication, and non-repudiation[4] are central to modern cryptography. Modern cryptography exists at the intersection of the German Lorenz cipher machine, disciplines of mathematics, computer science, electrical engineering, used in World War II to encrypt very- communication science, and physics. Applications of cryptography high-level general staff messages include electronic commerce, chip-based payment cards, digital currencies, computer passwords, and military communications. Cryptography prior to the modern age was effectively synonymous with encryption, converting information from a readable state to unintelligible nonsense. The sender of an encrypted message shares the decoding technique only with intended recipients to preclude access from adversaries. The cryptography literature often uses the names Alice ("A") for the sender, Bob ("B") for the intended recipient, and Eve ("eavesdropper") for the adversary.[5] Since the development of rotor cipher machines in World War I and the advent of computers in World War II, cryptography methods have become increasingly complex and its applications more varied. Modern cryptography is heavily based on mathematical theory and computer science practice; cryptographic algorithms are designed around computational hardness assumptions, making such algorithms hard to break in actual practice by any adversary. -
ISA 562 Information Security Theory & Practice
ISA 562 Information Security Theory & Practice Introduction to Cryptography Agenda • Basics & Definitions • Classical Cryptography • Symmetric (Secret Key) Cryptography • DES (Data Encryption Standard) • Multiple Encryptions • Modes of Block Cipher Operations • Math Essential • Asymmetric (Public Key) Cryptography 2 1 Basics & Definitions Security Concepts (I) • Confidentiality – Prevent information from being exposed to unintended party – Ex: An employee should not come to know the salary of his manager • Integrity – Assure that the information has not been tempered – Ex: An employee should not be able to modify the employee's own salary • Identity – Assure that the party of concern is authentic - it is what it claims to be – Ex: An employee should be able to uniquely identify and authenticate himself/herself 4 2 Security Concepts (II) • Availability – Assure that unused service or resource is available to legitimate users – Ex: Paychecks should be printed on time as stipulated by law • Anonymity – Assure that the identity of some party is remain anonymous – Ex: The manager should not know who had a critical review of him • Non-Repudiation – Assure that authenticated party has indeed done something that cannot be denied – Ex: Once the employee has cashed his paycheck, he can’t deny it. 5 Cryptography • Crypt = secret • Graph = writing • Cryptography is the science / art of transforming meaningful information into unintelligible text Becoming a science that relies on mathematics (number theory, algebra) • Cryptanalysis is the science / art of breaking cryptographic codes • Cryptology is the science / art / study of both cryptography and cryptanalysis 6 3 Applications of Cryptography • Assuring document integrity • Assuring document confidentiality • Authenticating parties • Document signature • Non-repudiation • Secure transactions • Exchanging keys • Sharing Secrets • Digital cash • Preserving anonymity • Copyright protection • More .