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Caesar Cipher for Beginners

The document describes an algorithm for encrypting and decrypting messages using Caesar cipher. It explains that in Caesar cipher each letter is shifted a fixed number of positions down the alphabet, and includes the mathematical formulas for encryption and decryption. It then provides a Java program that implements the Caesar cipher algorithm to encrypt and decrypt the message "Anna University" with a shift of 3. The program output verifies that the encryption and decryption was successful.

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Pradeep Pradeep
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100 views2 pages

Caesar Cipher for Beginners

The document describes an algorithm for encrypting and decrypting messages using Caesar cipher. It explains that in Caesar cipher each letter is shifted a fixed number of positions down the alphabet, and includes the mathematical formulas for encryption and decryption. It then provides a Java program that implements the Caesar cipher algorithm to encrypt and decrypt the message "Anna University" with a shift of 3. The program output verifies that the encryption and decryption was successful.

Uploaded by

Pradeep Pradeep
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Ex.

No : 1(a)
Encryption and Decryption Using Ceaser Cipher
Date :

AIM:

To encrypt and decrypt the given message by using Ceaser Cipher


encryption algorithm.

ALGORITHMS:

1. In Ceaser Cipher each letter in the plaintext is replaced by a letter some


fixed number of positions down the alphabet.
2. For example, with a left shift of 3, D would be replaced by A, E would
become B, and so on.
3. The encryption can also be represented using modular arithmetic by first
transforming the letters into numbers, according to the scheme, A = 0, B = 1,
Z = 25.
4. Encryption of a letter x by a shift n can be described mathematically as,
En(x) = (x + n) mod26
5. Decryption is performed similarly,
Dn (x)=(x - n) mod26

PROGRAM:
CaesarCipher.java
class caesarCipher {
public static String encode(String enc, int offset) {
offset = offset % 26 + 26;
StringBuilder encoded = new StringBuilder();
for (char i : enc.toCharArray()) {
if (Character.isLetter(i)) {
if (Character.isUpperCase(i)) {
encoded.append((char) ('A' + (i - 'A' + offset) % 26));
} else {
encoded.append((char) ('a' + (i - 'a' + offset) % 26));
}
} else {
encoded.append(i);
}
}
return encoded.toString();
}

public static String decode(String enc, int offset) {


return encode(enc, 26 - offset);
}

public static void main(String[] args) throws java.lang.Exception {


String msg = "Anna University";
System.out.println("Simulating Caesar Cipher\n------------------------");
System.out.println("Input : " + msg);
System.out.printf("Encrypted Message : ");
System.out.println(caesarCipher.encode(msg, 3));
System.out.printf("Decrypted Message : ");
System.out.println(caesarCipher.decode(caesarCipher.encode(msg, 3), 3));
}
}

OUTPUT:
Simulating Caesar Cipher
------------------------
Input : Anna University
Encrypted Message : Dqqd Xqlyhuvlwb
Decrypted Message : Anna University

RESULT:
Thus the program for ceaser cipher encryption and decryption algorithm has
been implemented and the output verified successfully.

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