├── README.md
├── SubstitutionCipher.java
├── LICENSE
└── CaesarCipher.java


/README.md:
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1 | # CGNS
2 | Cryptography secures data using encryption techniques, ensuring confidentiality and integrity. Network systems connect devices for data sharing, emphasizing communication, security, and efficiency.
3 | 


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/SubstitutionCipher.java:
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 1 | import java.io.*;
 2 | import java.util.*;
 3 | public class SubstitutionCipher {
 4 | static Scanner sc = new Scanner(System.in);
 5 | static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
 6 | public static void main(String[] args) throws IOException {
 7 | // TODO code application logic here
 8 | String a = "abcdefghijklmnopqrstuvwxyz";
 9 | String b = "zyxwvutsrqponmlkjihgfedcba";
10 | System.out.print("Enter any string: ");
11 | String str = br.readLine();
12 | String encrypt = "";
13 | char c;
14 | for(int i=0;i<str.length();i++)
15 | {
16 | c = str.charAt(i);
17 | int j = a.indexOf(c);
18 | encrypt = encrypt+b.charAt(j);
19 | }
20 | System.out.println("The encrypted data is: " +encrypt);
21 | }}


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/LICENSE:
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 1 | MIT License
 2 | 
 3 | Copyright (c) 2024 Abbireddy Venkata Chandu
 4 | 
 5 | Permission is hereby granted, free of charge, to any person obtaining a copy
 6 | of this software and associated documentation files (the "Software"), to deal
 7 | in the Software without restriction, including without limitation the rights
 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 9 | copies of the Software, and to permit persons to whom the Software is
10 | furnished to do so, subject to the following conditions:
11 | 
12 | The above copyright notice and this permission notice shall be included in all
13 | copies or substantial portions of the Software.
14 | 
15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 | SOFTWARE.
22 | 


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/CaesarCipher.java:
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 1 | import java.util.Scanner;
 2 | public class CaesarCipher {
 3 |         // Encrypt method
 4 |     public static String encrypt(String text, int k) {
 5 |         StringBuilder result = new StringBuilder();
 6 |         k = k % 26; // Ensure shift is within 0-25
 7 |         
 8 |         for (char c : text.toCharArray()) {
 9 |             if (Character.isUpperCase(c)) {
10 |                 char encryptedChar = (char) ('A' + (c - 'A' + k) % 26);
11 |                 result.append(encryptedChar);
12 |             } else if (Character.isLowerCase(c)) {
13 |                 char encryptedChar = (char) ('a' + (c - 'a' + k) % 26);
14 |                 result.append(encryptedChar);
15 |             } else {
16 |                 result.append(c); // Leave non-alphabetic characters unchanged
17 |             }
18 |         }
19 |         return result.toString();
20 |     }
21 | 
22 |     // Decrypt method
23 |     public static String decrypt(String text, int k) {
24 |         // Decrypting is the same as encrypting with a negative shift
25 |         return encrypt(text, 26 - (k % 26));
26 |     }
27 | 
28 |     public static void main(String[] args) {
29 |         Scanner scanner = new Scanner(System.in);
30 | 
31 |         System.out.print("Enter text: ");
32 |         String text = scanner.nextLine();
33 | 
34 |         System.out.print("Enter shift value: ");
35 |         int k = scanner.nextInt();
36 | 
37 |         // Encryption
38 |         String encryptedText = encrypt(text, k);
39 |         System.out.println("Encrypted Text: " + encryptedText);
40 | 
41 |         // Decryption
42 |         String decryptedText = decrypt(encryptedText, k);
43 |         System.out.println("Decrypted Text: " + decryptedText);
44 | 
45 |         scanner.close();
46 |     }
47 | }


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