Algorithms/JavaAlgorithms
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Add Playfair Cipher (#4988)

Browse Source
This commit is contained in:
Govind Gupta 2024-01-03 18:44:38 +05:30 committed by GitHub
parent a7d140a43e
commit 9bef5a169c
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 169 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
DIRECTORY.md
View File

@ -27,6 +27,7 @@
* [NonRepeatingNumberFinder](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/NonRepeatingNumberFinder.java)
* [NumbersDifferentSigns](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/NumbersDifferentSigns.java)
* [ReverseBits](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/ReverseBits.java)
* [SetKthBit](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/SetKthBit.java)
* [SingleBitOperations](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/SingleBitOperations.java)
* ciphers
* a5
@ -44,6 +45,7 @@
* [ColumnarTranspositionCipher](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/ColumnarTranspositionCipher.java)
* [DES](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/DES.java)
* [HillCipher](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/HillCipher.java)
* [PlayfairCipher](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/PlayfairCipher.java)
* [Polybius](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/Polybius.java)
* [ProductCipher](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/ProductCipher.java)
* [RSA](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/RSA.java)
@ -585,6 +587,7 @@
* [NonRepeatingNumberFinderTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/NonRepeatingNumberFinderTest.java)
* [NumbersDifferentSignsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/NumbersDifferentSignsTest.java)
* [ReverseBitsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/ReverseBitsTest.java)
* [SetKthBitTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/SetKthBitTest.java)
* [SingleBitOperationsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/SingleBitOperationsTest.java)
* ciphers
* a5
@ -592,6 +595,7 @@
* [BlowfishTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/BlowfishTest.java)
* [CaesarTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/CaesarTest.java)
* [DESTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/DESTest.java)
* [PlayfairTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/PlayfairTest.java)
* [PolybiusTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/PolybiusTest.java)
* [RSATest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/RSATest.java)
* [SimpleSubCipherTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/SimpleSubCipherTest.java)

128
src/main/java/com/thealgorithms/ciphers/PlayfairCipher.java Normal file
View File

@ -0,0 +1,128 @@
package com.thealgorithms.ciphers;
public class PlayfairCipher {
private char[][] matrix;
private String key;
public PlayfairCipher(String key) {
this.key = key;
generateMatrix();
}
public String encrypt(String plaintext) {
plaintext = prepareText(plaintext.replace("J", "I"));
StringBuilder ciphertext = new StringBuilder();
for (int i = 0; i < plaintext.length(); i += 2) {
char char1 = plaintext.charAt(i);
char char2 = plaintext.charAt(i + 1);
int[] pos1 = findPosition(char1);
int[] pos2 = findPosition(char2);
int row1 = pos1[0];
int col1 = pos1[1];
int row2 = pos2[0];
int col2 = pos2[1];
if (row1 == row2) {
ciphertext.append(matrix[row1][(col1 + 1) % 5]);
ciphertext.append(matrix[row2][(col2 + 1) % 5]);
} else if (col1 == col2) {
ciphertext.append(matrix[(row1 + 1) % 5][col1]);
ciphertext.append(matrix[(row2 + 1) % 5][col2]);
} else {
ciphertext.append(matrix[row1][col2]);
ciphertext.append(matrix[row2][col1]);
}
}
return ciphertext.toString();
}
public String decrypt(String ciphertext) {
StringBuilder plaintext = new StringBuilder();
for (int i = 0; i < ciphertext.length(); i += 2) {
char char1 = ciphertext.charAt(i);
char char2 = ciphertext.charAt(i + 1);
int[] pos1 = findPosition(char1);
int[] pos2 = findPosition(char2);
int row1 = pos1[0];
int col1 = pos1[1];
int row2 = pos2[0];
int col2 = pos2[1];
if (row1 == row2) {
plaintext.append(matrix[row1][(col1 + 4) % 5]);
plaintext.append(matrix[row2][(col2 + 4) % 5]);
} else if (col1 == col2) {
plaintext.append(matrix[(row1 + 4) % 5][col1]);
plaintext.append(matrix[(row2 + 4) % 5][col2]);
} else {
plaintext.append(matrix[row1][col2]);
plaintext.append(matrix[row2][col1]);
}
}
return plaintext.toString();
}
private void generateMatrix() {
String keyWithoutDuplicates = removeDuplicateChars(key + "ABCDEFGHIKLMNOPQRSTUVWXYZ");
matrix = new char[5][5];
int index = 0;
for (int i = 0; i < 5; i++) {
for (int j = 0; j < 5; j++) {
matrix[i][j] = keyWithoutDuplicates.charAt(index);
index++;
}
}
}
private String removeDuplicateChars(String str) {
StringBuilder result = new StringBuilder();
for (int i = 0; i < str.length(); i++) {
if (result.indexOf(String.valueOf(str.charAt(i))) == -1) {
result.append(str.charAt(i));
}
}
return result.toString();
}
private String prepareText(String text) {
text = text.toUpperCase().replaceAll("[^A-Z]", "");
StringBuilder preparedText = new StringBuilder();
char prevChar = '\0';
for (char c : text.toCharArray()) {
if (c != prevChar) {
preparedText.append(c);
prevChar = c;
} else {
preparedText.append('X').append(c);
prevChar = '\0';
}
}
if (preparedText.length() % 2 != 0) {
preparedText.append('X');
}
return preparedText.toString();
}
private int[] findPosition(char c) {
int[] pos = new int[2];
for (int i = 0; i < 5; i++) {
for (int j = 0; j < 5; j++) {
if (matrix[i][j] == c) {
pos[0] = i;
pos[1] = j;
return pos;
}
}
}
return pos;
}
public void printMatrix() {
System.out.println("\nPlayfair Cipher Matrix:");
for (int i = 0; i < 5; i++) {
for (int j = 0; j < 5; j++) {
System.out.print(matrix[i][j] + " ");
}
System.out.println();
}
}
}

37
src/test/java/com/thealgorithms/ciphers/PlayfairTest.java Normal file
View File

@ -0,0 +1,37 @@
package com.thealgorithms.ciphers;
import static org.junit.jupiter.api.Assertions.*;
import org.junit.jupiter.api.Test;
public class PlayfairTest {
@Test
public void testEncryption() {
PlayfairCipher playfairCipher = new PlayfairCipher("KEYWORD");
String plaintext = "HELLO";
String encryptedText = playfairCipher.encrypt(plaintext);
assertEquals("GYIZSC", encryptedText);
}
@Test
public void testDecryption() {
PlayfairCipher playfairCipher = new PlayfairCipher("KEYWORD");
String encryptedText = "UDRIYP";
String decryptedText = playfairCipher.decrypt(encryptedText);
assertEquals("NEBFVH", decryptedText);
}
@Test
public void testEncryptionAndDecryption() {
PlayfairCipher playfairCipher = new PlayfairCipher("KEYWORD");
String plaintext = "PLAYFAIR";
String encryptedText = playfairCipher.encrypt(plaintext);
String decryptedText = playfairCipher.decrypt(encryptedText);
assertEquals(plaintext, decryptedText);
}
}