DOCSLIB.ORG

CS 105 - Lab 9

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
CS 105 - Lab 9 CS 105 - Lab 9 Today, you will be implementing three different ciphers! There's a very weak Caesar cipher, a similarly weak Transpositional cipher, and a stronger but not impenetrable Vigenere cipher. Let's get into it. Part 1: ROT13 The first cipher that we're going to implement is a simple one that is trivial to break if you know a ciphertext is using it. ROT13, also called the Caesar cipher, was developed in ancient Rome and is a simple substitution cipher. ROT13 is terrible for encryption, but is used as a classic example for weak encryption. Let's make it in Python! Open up Spyder and create a file called rot13encrypt.py. # ROT13 encrypter # define our alphabet alphabet = list('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz') # get a phrase as user input phrase = input('Enter a phrase to encode: ') # for each character in our phrase for character in phrase: # if the character is a letter in our alphabet, shift it by 13 # and add it to our encrypted string index = alphabet.index(character) print(alphabet[index-13], end='') Run this script and input your first name only. What is the output? Try re-running the program with your first name, a space, and your last name. The program should crash. Write down the error that you receive. Why do you think the program doesn't work with punctuation such as spaces? # ROT13 encrypter # define our alphabet alphabet = list('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz') # get a phrase as user input phrase = input('Enter a phrase to encode: ') # for each character in our phrase for character in phrase: # if the character is a letter in our alphabet, shift it by 13 # and add it to our encrypted string try: index = alphabet.index(character) print(alphabet[index-13], end='') # otherwise, add the symbol to our encrypted string without processing it except ValueError: print(character, end='') Modify the program to include try... except blocks that will prevent the program from crashing. If you haven't used try statements before, their purpose is quite literally to try to execute some code that might generate errors that you've planned for. The error we've planned for in this case is ValueError, which happens when we try to find the index of a character that isn't in a list. Now, create a new file called rot13decode.py that decodes ROT13 back into plaintext. You'll need to shift 13 characters to the right instead of the left. Be aware that you may get an error if you shift past the end of the alphabet. You can fix the problem of shifting off the list by employing a solution like the following: my_list[index + shift_amount % len(my_list)]. Of course, you'll need to change this formula to meet the needs of the problem we're trying to solve (shifting alphabet by 13). Part 2 - Transposition Cipher Now we're going to look at a different type of cipher which involves moving characters around rather than substitutions of letters. If you've ever played the newspaper game Jumble you have used a Transposition cipher. The one that we're going to work with today is the Rail Fence cipher. The Rail Fence cipher is also known as the Zig Zag Cipher, as it hides its text in a diagonal pattern. Read about how it works at http://crypto.interactive-maths.com/rail-fence-cipher.html#intro If you read the above message diagonally, you'll see that it reads "DEFENDTHEEASTWALLXX". We're going to make our own version of this cipher but excluding the x's. Following the tutorial on the page listed above, decode the following message: ACDTAKTANTAW. Use the grid and write your final answer to the right. Now, encode the message PYTHONRULES!. Put your message on the right. Remember that symbols can be used in transpotition ciphers since we aren't doing any substitutions. The rail cipher encoder is pretty easy to write in Python if you keep the same number of rails each time, though the decoder is a bit more difficult. Today you'll just be writing the encoder. # rail fence cipher encoder # input a message message = # make a list called rails with three blank strings rails = # make a zig-zag path for them to follow rail_path = [0,1,2,1] for index, letter in enumerate(message): # for each letter, add it to the correct rail on the path rails[rail_path[index % 4]] += letter # create a string of all three rails concatenated together (rail 0 + rail 1 + rail 2) out = print(out) Fill in the remaining code in Spyder and save this as rail_encode.py. Run it and make sure that PYTHONRULES! is the same on this program as your manual encoding of it. What would you say the weaknesses of this ciper are, even if you can use more or less than 3 rails? Part 3 - Vigenere Cipher You already learned in class about the basics of the Vigenere cipher. Now its time to make it in code! If you don't remember, the Vigenere Cipher is an alphanumeric cipher that combines multiple Caesar ciphers into one. You start off with two values, a plaintext message and a codeword. For example, let's use ATTACKATDAWN as the plaintext message and LEMON as the codeword. The codeword wraps around the plaintext if it's not long enough as shown: Plain: ATTACKATDAWN Code: LEMONLEMONLE Now, for each combination of (plaintext letter, codeword letter), we find the intersection of the two letters on the substitution matrix and write down the letters. In our example, the result would be: (A,L) = L (T,E) = X (T,M) = F (A,O) = O (C,N) = P and so on. According to Wikipedia, this can be done mathematically: Write your first and last name using the Vigenere cipher and the key . Don't use spaces. COMPSCI This is the way we're going to do our program: with numbers! A few things to note: If we have an alphabet string alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', we can get a numeric value from 0 to 25 with alphabet.index(letter). For example, alphabet.index('a') = 0. Your program will first ask for a message and a temporary key, putting each into uppercase. The temporary key will then be stripped of all spaces, numbers, and punctuation marks. The key needs to be letters only. The way to do this is to use a for loop for each letter in the temporary key. Check if each letter is a letter by using letter.isalpha(). If the letter is a letter, add it to a new string called key. Now that we have a key and a message, iterate through each letter in the message: converting it to a number from 0 to 25. getting the proper key letter at the position in the message. adding the two together and modding by 26 Start with the skeleton code I provide: # Vigenere cipher # define our alphabet alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' # define our cipher encoder def vig_encode(message, temp_key): # strip numbers and whitespace from the key # create an empty key string key = '' # for each character in the temporary key for # if the character is a letter if # add the letter to the new key string # create a blank string out = '' # for each letter in the message for index, letter in enumerate(message): try: # get the letter's position in the alphabet m = # get the key's position in the alphabet (Key may be shorter than msg!) k = # add the two together and mod by 26 c = # print the result's position in the alphabet out += alphabet[c] except ValueError: # print the punctuation out += message[i] return out # input message and key, converting each to UPPERCASE. message = temp_key = print(vig_encode(message,temp_key)) Finish the skeleton code. Any line that ends with an = or has an if or a for statement and nothing after it you'll need to finish yourself. Write down the program's output for FURMANPALADINS with codeword PURPLE. Change the encrpytion program to a decryption program. This can be done by changing one symbol. What is it that we're changing? What would you say are the weaknesses of this cipher? .
Load more

Recommended publications
  • A Cipher Based on the Random Sequence of Digits in Irrational Numbers
    https://doi.org/10.48009/1_iis_2016_14-25 Issues in Information Systems Volume 17, Issue I, pp. 14-25, 2016 A CIPHER BASED ON THE RANDOM SEQUENCE OF DIGITS IN IRRATIONAL NUMBERS J. L. González-Santander, [email protected], Universidad Católica de Valencia “san Vicente mártir” G. Martín González. [email protected], Universidad Católica de Valencia “san Vicente mártir” ABSTRACT An encryption method combining a transposition cipher with one-time pad cipher is proposed. The transposition cipher prevents the malleability of the messages and the randomness of one-time pad cipher is based on the normality of "almost" all irrational numbers. Further, authentication and perfect forward secrecy are implemented. This method is quite suitable for communication within groups of people who know one each other in advance, such as mobile chat groups. Keywords: One-time Pad Cipher, Transposition Ciphers, Chat Mobile Groups Privacy, Forward Secrecy INTRODUCTION In cryptography, a cipher is a procedure for encoding and decoding a message in such a way that only authorized parties can write and read information about the message. Generally speaking, there are two main different cipher methods, transposition, and substitution ciphers, both methods being known from Antiquity. For instance, Caesar cipher consists in substitute each letter of the plaintext some fixed number of positions further down the alphabet. The name of this cipher came from Julius Caesar because he used this method taking a shift of three to communicate to his generals (Suetonius, c. 69-122 AD). In ancient Sparta, the transposition cipher entailed the use of a simple device, the scytale (skytálē) to encrypt and decrypt messages (Plutarch, c.
    [Show full text]
  • Secret Wri0ng Steganography
    Secret wring LIVITCSWPIYVEWHEVSRIQMXLEYVEOIEWHRXEXIP FEMVEWHKVSTYLXZIXLIKIIXPIJVSZEYPERRGERI MWQLMGLMXQERIWGPSRIHMXQEREKIETXMJTPRGEV EKEITREWHEXXLEXXMZITWAWSQWXSWEXTVEPMRXR SJGSTVRIEYVIEXCVMUIMWERGMIWXMJMGCSMWXSJ OMIQXLIVIQIVIXQSVSTWHKPEGARCSXRWIEVSWII BXVIZMXFSJXLIKEGAEWHEPSWYSWIWIEVXLISXLI VXLIRGEPIRQIVIIBGIIHMWYPFLEVHEWHYPSRRFQ MXLEPPXLIECCIEVEWGISJKTVWMRLIHYSPHXLIQI MYLXSJXLIMWRIGXQEROIVFVIZEVAEKPIEWHXEAM WYEPPXLMWYRMWXSGSWRMHIVEXMSWMGSTPHLEVHP FKPEZINTCMXIVJSVLMRSCMWMSWVIRCIGXMWYMX CSCI 470: Web Science • Keith Vertanen • Copyright © 2014 Overview • Secret wri+ng – Steganography – Cryptography • Keys, plaintext, ciphertext • Codes vs. Ciphers • Transposi+on ciphers • Subs+tu+on ciphers 2 Steganography vs. Cryptography • Steganography – "concealed wri+ng" – Hide messages to keep secret – Does not aract aen+on (iF not Found). • Cryptography – "hidden wring" – Scramble messages so unintelligible – Screams: "Please try and decode me!" • But not mutually exclusive: – e.g. Scrambled message in "invisible" ink 3 Physical hiding • Ancient Chinese – Write message on very thin silk sheet – Rolled up, covered in wax, and ingested by messenger • 480 BC – His+aeus wants Aristagoras oF Miletus to revolt against the Persian King • Shaves head oF messenger, taoos message on scalp • Wait For hair to grow back • Sends messenger to Aristagoras 4 Physical hiding • 480 BC – Demaratus, Greek ex-pat living in Persia – No+ces build up For aack on Greece – Sent secret messages: • Scraped wax oF tablet • Wrote on wood • Covered up with wax – Persian ships
    [Show full text]
  • 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.
    [Show full text]
  • Enigma Cryptanalysis - Beginnings
    Enigma Cryptanalysis - Beginnings Gaurish Korpal∗ [email protected] July 15, 2015 Abstract Any message may be hidden in two basic ways. The methods of steganography conceal the very existence of the message, for example invisible inks and microdots. The methods of cryptography, on the other hand, do not conceal the presence of a secret message but render it unintelligible as ciphertext, to outsiders by various transformations of the plaintext. Breaking ciphers require ingenuity, creativity and a little math. In this article our focus will be on breaking Enigma ciphers. The skill involved in breaking ciphers is called cryptanalysis. Keywords. Enigma, cryptanalysis, cypher, Caesar, Vigen`ere,Rejewski, Zygalski, Bomba, Bombe 1 Cipher not Code A code is a mapping from some meaningful unit (word, sentence, phrase) into something else (usually a shorter group of symbols). A code requires a codebook, it is simply a list of these mappings. For example we could make up a code where the word Apple is written as 67, historical example of this is \Zimmermann Telegram Code" for more details refer [7]. Ciphers do not involve meaning. Instead they are mechanical operations (known as algorithms) which are performed on the individual or small chunks of letters. A code is stored as a mapping in a codebook, while ciphers transform individual symbols according to an algorithm. It was definitively stated in 1883 by the Dutch linguist Auguste Kerckhoffs von Nieuwenhof in his book La Cryptographie militaire: Kerckhoffs' Principle: The security of a cryptosystem must not depend on keeping secret the crypto-algorithm. The security depends only on keeping secret the key.
    [Show full text]
  • Grade 6 Math Circles Cryptography Solutions Atbash Cipher Caesar Cipher
    Faculty of Mathematics Centre for Education in Waterloo, Ontario N2L 3G1 Mathematics and Computing Grade 6 Math Circles November 5/6 2019 Cryptography Solutions Hello World Khoor Zruog Hello Zruog Khoor Khoor Zruog World 1. Person A encrypts plaintext 2. Person B receives ciphertext 3. Person B decrypts ciphertext back into ciphertext into plaintext Atbash Cipher Examples 1. Encrypt \Math Circles" using the Atbash cipher. Nzgs Xrixovh 2. Decrypt \ORLM PRMT" using the Atbash cipher. LION KING Caesar Cipher Examples: Encrypt or decrypt the following messages using the shift number given in parentheses: a) Welcome to Math Circles! (5) Bjqhtrj yt Rfym Hnwhqjx! plaintext A B C D E F G H I J K L M N O P Q R S T U V W X Y Z ciphertext F G H I J K L M N O P Q R S T U V W X Y Z A B C D E 1 b) Ljw hxd anjm cqrb? (9) Can you read this? plaintext A B C D E F G H I J K L M N O P Q R S T U V W X Y Z ciphertext J K L M N O P Q R S T U V W X Y Z A B C D E F G H I c) What if I did a Caesar Shift of 26 units on \Welcome to Math Circles!"? A Caesar shift of 26 would be shifting by the length of the alphabet. For example I would be shifting A 26 letters to the right.
    [Show full text]
  • Q.1 What Is Cryptography? Ans. Cryptographic
    WWW.UPTUNOTES.COM Q.1 What is cryptography? Ans. Cryptographic systems are generally classified along 3 independent dimensions: Type of operations used for transforming plain text to cipher text All the encryption algorithms are based on two general principles: substitution, in which each element in the plaintext is mapped into another element, and transposition, in which elements in the plaintext are rearranged. The number of keys used are: 1. If the sender and receiver uses same key then it is said to be symmetric key (or) single key (or) conventional encryption. 2. If the sender and receiver use different keys then it is said to be public key encryption. Q.2 Explain the Cryptanalysis? Ans. The process of attempting to discover X or K or both is known as cryptanalysis. The strategy used by the cryptanalysis depends on the nature of the encryption scheme and the information available to the cryptanalyst. Q.3 Write down the various types of cryptanalytic attacks? Ans. There are various types of cryptanalytic attacks based on the amount of information known to the cryptanalyst. 1. Cipher Text Only – A copy of cipher text alone is known to the cryptanalyst. 2. Known Plaintext – The cryptanalyst has a copy of the cipher text and the corresponding plaintext. 3. Chosen Plaintext – The cryptanalysts gains temporary access to the encryption machine. They cannot open it to find the key, however; they can encrypt a large number of suitably chosen plaintexts and try to use the resulting cipher texts to deduce the key. 4. Chosen Cipher Text – The cryptanalyst obtains temporary access to the decryption machine, uses it to decrypt several string of symbols, and tries to use the results to deduce the key.
    [Show full text]
  • Breaking Transposition Cipher with Genetic Algorithm
    Breaking Transposition Cipher with Genetic Algorithm C.Obi Reddy, National University of Singapore(NUS), ECE Department, [email protected] Abstract: In recent years a number of example total number of letters is 20 optimisation algorithms have emerged which is regular case with the key order of which have proven to be effective in 5. If the plain text is irregular then solving a variety of NP-complete padding of X is done at the tail of the text problems. In this paper an example the to make it regular. kind in cryptanalysis, breaking of Encryption of plain text is done as follows transposition cipher using a heuristic genetic algorithm is presented. Regular: Plain 1 2 3 4 5 Introduction: Text In the Brute Force attack the attacker Key 1 4 2 5 3 tries every possible (k! Keys) key on a T H I S I piece of cipher text until an intelligible S A S I M translation into plaintext is obtained. P L E M E Many types of classical ciphers exist, S S A G E although most fall into one of two broad categories: substitution ciphers and Cipher Text: TSPS ISEA IMEE HALS SIMG transposition ciphers. In the former one, every plaintext character is substituted by Irregular: a cipher character, using a substitution Plain 1 2 3 4 5 alphabet, and in the latter one, plaintext Text characters are permuted using a Key 1 4 2 5 3 predetermined permutation. T H I S I S A S I M Transposition cipher works by breaking P L E M E the plain text in to fixed number of blocks S S A G E and then shuffling the characters in each block according to the agreed key K.
    [Show full text]
  • Download Magzter App from Andriod Apple Store Rakesh U Kishore P
    INTERVIEW-Samir INTERVIEW:VijayMinocha REGULATIONS COGOPORT TERMINALS:Dowe JShah:“Pro-actively "IoTwillDriveGreater EaseofTrade TheDigitalEraof NeedAutomated ComplytoTFAREGIME” Efficiency” throughTFA MovingCargo Terminals? South Asia’s premier maritime business magazine `100 AUGUST 2017 WWW.MARITIMEGATEWAY.COM RNI NO: TELENG/2009/30633 POSTAL REGISTRATION NO: LII/RNP/HD/1137/2016-18 TheCruiseandTheGoldenEgg DATE OF PUBLICATION: 26/07/2017 DATE OF POSTING: 28/07/2017 CYBERCYBER AATTTTACKSACKS WILLWILL HURTHURT YYOUOU BEBE PREPPREPAREDARED TOTO DEALDEAL WITHWITH ESCALAESCALATINGTING OFFENSIVESOFFENSIVES 02 MARITIME GATEWAY / AUGUST 2017 Automate, connect and control with Cavotec’s inspired engineering. Cavotec is a global engineering group that manufactures power transmission, distribution and control technologies that form the link between fixed and mobile equipment in the Ports & Maritime, Airports, Mining & Tunnelling and General Industry sectors. Cavotec India Pvt Ltd Telephone: +91 20 6725 5000 Fax: +91 20 6725 5099 [email protected] Inspired Engineering www.cavotec.com FROM THE EDITOR Watch Out! The e-pirates are at sea here do you think the formal maritime cyber security cell, hackers are going to play vessel operators should protect their their favourite sport next? three keys navigational systems- GPS, WYes, at sea. The shipping AIS and ECDIS. industry that transports 90 per cent Of late, many vessels have left Somali Reliance on of the world’s trade has made itself pirates smarting by turning off the increasingly susceptible to cyber threats. AIS or faking a location to divert the automation cannot With shipping companies making a lot attention of the mischief makers. compromise cyber of data accessible to their customers However, it is only a matter of time through their mobile applications, the when these faceless pirates can security.
    [Show full text]
  • Lecture 2: Classical Cryptography
    Lecture 2: Classical Cryptography Data and Information Management: ELEN 3015 School of Electrical and Information Engineering, University of the Witwatersrand Introduction Monoalphabetic Cipher - Frequency analysis Classical Ciphers Other Substitution Ciphers Transposition ciphers Stream vs Block Enciphering 1. Homework hqfubswlrq lv d phdqv ri dwwdlqlqj vhfxuh frpsxwdwlrq ryhu lqvhfxuh fkdqqhov eb xvlqj hqfubswlrq zh glvjxlvh wkh phvvdjh vr wkdw hyhq li wkh wudqvplvvlrq lv glyhuwhg wkh phvvdjh zloo qrw eh uhyhdohg 1. Monoalphabetic Cipher - Frequency analysis Do a frequency analysis Letter distribution of English language is fixed (for a large body of text) Tables of letter distribution For instance, most commonly used letter is \e" 1. Monoalphabetic Cipher - Frequency analysis 1. Monoalphabetic Cipher - Answer ENCRYPTION IS A MEANS OF ATTAINING SECURE COMMUNICATION OVER INSECURE CHANNELS BY USING ENCRYPTION WE DISGUISE THE MESSAGE SO THAT EVEN IF THE TRANSMISSION IS DIVERTED THE MESSAGE WILL NOT BE REVEALED 2. Classical Ciphers How do we increase security of the monoalphabetic cipher? 3. Polyalphabetic ciphers Use more than one alphabetic substitution to flatten the frequency distribution Combine substitutions that are high with those that are low Eg use: • P1(a) = (a*3)mod26 • P2(a) = ((5*a)+13)mod26 3. Polyalphabetic ciphers Cipher I: ABCDEFG ::: STUVWXYZ a d g j m p s ::: c f i l o r u x Cipher II: ABCDEFG ::: STUVWXYZ n s x c h m r ::: z e j o t y d i 3. Polyalphabetic ciphers - Frequency distribution 3. Vigenere tables a b c d e f ::: t u v w x y z π A a b c d e f ::: t u v w x y z 0 B b c d e f g ::: u v w x y z a 1 C c d e f g h ::: v w x y z a b 2 .
    [Show full text]
  • Crypyto Documentation Release 0.2.0
    crypyto Documentation Release 0.2.0 Yan Orestes Aug 22, 2018 API Documentation 1 Getting Started 3 1.1 Dependencies...............................................3 1.2 Installing.................................................3 2 Ciphers 5 2.1 Polybius Square.............................................5 2.2 Atbash..................................................6 2.3 Caesar Cipher..............................................7 2.4 ROT13..................................................8 2.5 Affine Cipher...............................................9 2.6 Rail Fence Cipher............................................9 2.7 Keyword Cipher............................................. 10 2.8 Vigenère Cipher............................................. 11 2.9 Beaufort Cipher............................................. 12 2.10 Gronsfeld Cipher............................................. 13 3 Substitution Alphabets 15 3.1 Morse Code............................................... 15 3.2 Binary Translation............................................ 16 3.3 Pigpen Cipher.............................................. 16 3.4 Templar Cipher.............................................. 18 3.5 Betamaze Alphabet............................................ 19 Python Module Index 21 i ii crypyto Documentation, Release 0.2.0 crypyto is a Python package that provides a set of cryptographic tools with simple use to your applications. API Documentation 1 crypyto Documentation, Release 0.2.0 2 API Documentation CHAPTER 1 Getting Started These instructions
    [Show full text]
  • Rail Fence Cipher Columnar Transposition
    Mathematics 124 (Winter 2009) Transposition Ciphers A transposition cipher is one in which plaintext symbols are rearranged (i.e., transposed or permuted) to produce ciphertext. The method of transposition may be either mathematical or typographical in nature. Rail Fence Cipher Example: We encipher NOTHING IS AS IT SEEMS by first writing it on two lines in a zig-zag pattern (or rail fence). The ciphertext is produced by transcribing the first row followed by the second row. NTIGSSTEM OHNIAISES Ciphertext: NTIGS STEMO HNIAI SES. To decrypt, we write half the letters on one line, half on the second. (Note that if there are an odd number of letters, we include the “middle” letter on the top line.) Example: Decipher MKHSE LWYAE ATSOL. Solution: Since there are 15 letters, we write 8 on the top line and 7 on the bottom line so that MKHSELWY AEATSOL Plaintext: MAKE HASTE SLOWLY. Columnar Transposition The number of columns is the key information. To encipher: Plaintext is written horizontally in k columns, and is then transcribed vertically column- by-column, To decipher: Suppose that the length of the ciphertext is n and the key is k. Then the letters will fill n DIV k full rows, and there will be one partial row at the end with n MOD k letters. Transcribing row-by-row will then yield the plaintext. Example: Encrypt NOTHING IN THE WORLD IS MORE DANGEROUS THAN SINCERE IGNORANCE AND CONSCIENTIOUS STUPIDITY with a key of k = 9 columns. Solution: We write the plaintext horizontally in 9 columns as follows: NOTHINGIN THEWORLDI SMOREDANG EROUSTHAN SINCEREIG NORANCEAN DCONSCIEN TIOUSSTUP IDITY The cipher text is therefore: NTSES NDTIO HMRIO CIDTE OONRO OIHWR UCANU TIOES ENSSY NRDTR CCSGL AHEEI TIDNA IAEUN IGNGN NP.
    [Show full text]
  • Transposition Cipher in Cryptography, a Transposition Cipher Is a Method of Encryption by Which the Positions Held by Units of P
    Transposition cipher In cryptography, a transposition cipher is a method of encryption by which the positions held by units of plaintext (which are commonly characters or groups of characters) are shifted according to a regular system, so that the ciphertext constitutes a permutation of the plaintext. That is, the order of the units is changed. Mathematically a bijective function is used on the characters' positions to encrypt and an inverse function to decrypt. Following are some implementations. Contents • 1 Rail Fence cipher • 2 Route cipher • 3 Columnar transposition • 4 Double transposition • 5 Myszkowski transposition • 6 Disrupted transposition • 7 Grilles • 8 Detection and cryptanalysis • 9 Combinations • 10 Fractionation Rail Fence cipher The Rail Fence cipher is a form of transposition cipher that gets its name from the way in which it is encoded. In the rail fence cipher, the plaintext is written downwards on successive "rails" of an imaginary fence, then moving up when we get to the bottom. The message is then read off in rows. For example, using three "rails" and a message of 'WE ARE DISCOVERED. FLEE AT ONCE', the cipherer writes out: W . E . C . R . L . T . E . E . R . D . S . O . E . E . F . E . A . O . C . A . I . V . D . E . N . Then reads off: WECRL TEERD SOEEF EAOCA IVDEN (The cipherer has broken this ciphertext up into blocks of five to help avoid errors.) Route cipher In a route cipher, the plaintext is first written out in a grid of given dimensions, then read off in a pattern given in the key.
    [Show full text]