Name: Dil Prasad Kuwor Roll no. : 064/02 Subject: Cryptography Assignment no. : Lab No. 2
Date: 9/22/2010
Q.1 Generate the Caesar cipher text of given plain text and also decrypt the generated cipher text. Also give the user the facility to change the value of key. Testing Data Encryption Plain Text :- meet me after the toga party Cipher Text :- PHHW PH DIWHU WKH WRJD SDUWB ( n = 3) Decryption Cipher Text :- khoor eurwkhu Plain Text :- HELLO BROTHER
Java Code: import java.util.*; class CeasarCipher { public static void findPlainText() { String letter[] = {"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" }; String plainText="", cipherTxt; System.out.println("Enter System.out.println("Enter a ciphertext"); Scanner in = new Scanner(System.in); Scanner(System.in); cipherTxt = in.nextLine(); int index = 0; for(int i=0; i
index = (25 - index); plainText = plainText + letter[index]; letter[index]; } else { plainText = plainText + letter[index - 3]; } } } System.out.println("Plain System.out.println("Plain text of "+cipherTxt+" is "+ plainText); } public static void findCeaserCipher() findCeaserCipher() { String letter[] = {"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" }; String plainText, cipherTxt = ""; System.out.println("Enter System.out.println("Enter a plaintext"); Scanner in = new Scanner(System.in); plainText = in.nextLine(); int index = 0; for(int i=0; i
22) { index = (index + 3) % 26; cipherTxt = cipherTxt + letter[index]; } else { cipherTxt = cipherTxt + letter[index + 3]; }
}
2
} System.out.println("Cipher System.out.println("Cipher text of "+plainText+" is "+ cipherTxt); } public static void main (String[] args) { Scanner in = new Scanner(System.in); System.out.println("Enter System.out.println("Enter the choice:"); System.out.println("1. System.out.println("1. Plain text to cipher text."); System.out.println("2. System.out.println("2. cipher text to plain text."); int choice = in.nextInt(); switch(choice) { case 1: findCeaserCipher(); break; case 2: findPlainText(); break; default: System.out.printf("Invalide System.out.printf("Invalide Choice"); break; } } } Output:
3
