P8.10 Playfair cipher. Another way of thwarting a simple letter frequency analysis of an encrypted text is to encrypt pairs of letters together. A simple scheme to do this is the Playfair cipher. You pick a keyword and remove duplicate letters from it. Then you fill the keyword, and the remaining letters of the alphabet, into a 5 x 5 square. (Since there are only 25 squares, I and J are considered the same letter.) Here is such an arrangement with the keyword PLAYFAIR. PLAYF IRBCD EGHKM NOQST UVWXZ To encrypt a letter pair, say AM, look at the rectangle with corners A and M: PLAYF IRBCD EGHKM NOQST UVWXZ The encoding of this pair is formed by looking at the other two corners of the rectangle, in this case, FH. If both letters happen to be in the same row or column, such as GO, simply swap the two letters. Decryption is done in the same way. Write a program that encrypts or decrypts an input text according to this cipher.

P8.10 Playfair cipher. Another way of thwarting a simple letter frequency analysis of an encrypted text is to encrypt pairs of letters together. A simple scheme to do this is the Playfair cipher. You pick a keyword and remove duplicate letters from it. Then you fill the keyword, and the remaining letters of the alphabet, into a 5 x 5 square. (Since there are only 25 squares, I and J are considered the same letter.) Here is such an arrangement with the keyword PLAYFAIR. PLAYF IRBCD EGHKM NOQST UVWXZ To encrypt a letter pair, say AM, look at the rectangle with corners A and M: PLAYF IRBCD EGHKM NOQST UVWXZ The encoding of this pair is formed by looking at the other two corners of the rectangle, in this case, FH. If both letters happen to be in the same row or column, such as GO, simply swap the two letters. Decryption is done in the same way. Write a program that encrypts or decrypts an input text according to this cipher.

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Substitution ciphers are encryption/decryption algorithms that replace one letter or number with another. The first attested use of a substitution cipher in military affairs was by Julius Caesar, described by him in Gallic Wars (cf. Kahn pp83-84). In caesar cipher , you replace each letter by 3rd letter on. If it is out of bound (later than Z), then round to the head (letter A) and continue the shift. For example:meet me after the toga party PHHW PH DIWHU WKH WRJD SDUWB Please write a program in Java to implement the Caesar Cipher: a. Implement the encryption algorithm. Ask the user to input one all lower case normal sentence (called plaintext) using the nextLine method, and then output the encrypted text (called ciphertext). b. Implement the decryption algorithm. Ask the user to input one encrypted sentence (i.e. ciphertext) using the nextLine method, and then output the decrypted text (i.e. plaintext).
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In cryptography, a Caesar cipher is a very simple encryption techniques in which each letter in the plain text is replaced by a letter some fixed number of positions down the alphabet. For example, with a shift of 3, A would be replaced by D, B would become E, and so on. The method is named after Julius Caesar, who used it to communicate with his generals. ROT-13 (“rotate by 13 places”) is a widely used example of a Caesar cipher where the shift is 13. In Python, the key for ROT-13 may be represented by means of the following dictionary: key = {‘a’:’n’, ‘b’:’o’, ‘c’:’p’, ‘d’:’q’, ‘e’:’r’, ‘f’:’s’, ‘g’:’t’, ‘h’:’u’,‘i’:’v’, ‘j’:’w’, ‘k’:’x’, ‘l’:’y’, ‘m’:’z’, ‘n’:’a’, ‘o’:’b’, ‘p’:’c’,‘q’:’d’, ‘r’:’e’, ‘s’:’f’, ‘t’:’g’, ‘u’:’h’, ‘v’:’i’, ‘w’:’j’, ‘x’:’k’,‘y’:’l’, ‘z’:’m’, ‘A’:’N’, ‘B’:’O’, ‘C’:’P’, ‘D’:’Q’, ‘E’:’R’, ‘F’:’S’,‘G’:’T’, ‘H’:’U’, ‘I’:’V’, ‘J’:’W’, ‘K’:’X’, ‘L’:’Y’, ‘M’:’Z’, ‘N’:’A’,‘O’:’B’, ‘P’:’C’, ‘Q’:’D’, ‘R’:’E’, ‘S’:’F’, ‘T’:’G’, ‘U’:’H’, ‘V’:’I’,‘W’:’J’, ‘X’:’K’,…
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