diff --git a/DIRECTORY.md b/DIRECTORY.md index 7ebc176b02cf..bb32c051a333 100644 --- a/DIRECTORY.md +++ b/DIRECTORY.md @@ -50,6 +50,7 @@ * [AES](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/AES.java) * [AESEncryption](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/AESEncryption.java) * [AffineCipher](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/AffineCipher.java) + * [AtbashCipher](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/AtbashCipher.java) * [Autokey](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/Autokey.java) * [Blowfish](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/Blowfish.java) * [Caesar](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/Caesar.java) @@ -59,6 +60,7 @@ * [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) + * [RailFenceCipher](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/RailFenceCipher.java) * [RSA](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/RSA.java) * [SimpleSubCipher](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/SimpleSubCipher.java) * [Vigenere](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/Vigenere.java) @@ -663,6 +665,7 @@ * [LFSRTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/a5/LFSRTest.java) * [AESEncryptionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/AESEncryptionTest.java) * [AffineCipherTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/AffineCipherTest.java) + * [AtbashTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/AtbashTest.java) * [AutokeyTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/AutokeyTest.java) * [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) @@ -671,6 +674,7 @@ * [HillCipherTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/HillCipherTest.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) + * [RailFenceTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/RailFenceTest.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) * [VigenereTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/VigenereTest.java) diff --git a/src/main/java/com/thealgorithms/ciphers/AtbashCipher.java b/src/main/java/com/thealgorithms/ciphers/AtbashCipher.java new file mode 100644 index 000000000000..c3b673144c63 --- /dev/null +++ b/src/main/java/com/thealgorithms/ciphers/AtbashCipher.java @@ -0,0 +1,71 @@ +package com.thealgorithms.ciphers; + +/** + * The Atbash cipher is a simple substitution cipher that replaces each letter + * in the alphabet with its reverse. + * For example, 'A' becomes 'Z', 'B' becomes 'Y', and so on. It works + * identically for both uppercase and lowercase letters. + * It's a symmetric cipher, meaning applying it twice returns the original text. + * Hence, the encrypting and the decrypting functions are identical + * @author https://github.com/Krounosity + * Learn more: https://en.wikipedia.org/wiki/Atbash + */ + +public class AtbashCipher { + + private String toConvert; + + // Default constructor. + AtbashCipher() { + } + + // String setting constructor. + AtbashCipher(String str) { + toConvert = str; + } + + // String getter method. + public String getString() { + return toConvert; + } + + // String setter method. + public void setString(String str) { + toConvert = str; + } + + // Checking whether the current character is capital. + private boolean isCapital(char ch) { + return ch >= 'A' && ch <= 'Z'; + } + + // Checking whether the current character is smallcased. + private boolean isSmall(char ch) { + return ch >= 'a' && ch <= 'z'; + } + + // Converting text to atbash cipher code or vice versa. + public String convert() { + + // Using StringBuilder to store new string. + StringBuilder convertedString = new StringBuilder(); + + // Iterating for each character. + for (char ch : toConvert.toCharArray()) { + + // If the character is smallcased. + if (isSmall(ch)) { + convertedString.append((char) ('z' - (ch - 'a'))); + } + // If the character is capital cased. + else if (isCapital(ch)) { + convertedString.append((char) ('Z' - (ch - 'A'))); + } + // Non-alphabetical character. + else { + convertedString.append(ch); + } + } + return convertedString.toString(); + } +} diff --git a/src/main/java/com/thealgorithms/ciphers/RailFenceCipher.java b/src/main/java/com/thealgorithms/ciphers/RailFenceCipher.java new file mode 100644 index 000000000000..5e53bdc7c4c8 --- /dev/null +++ b/src/main/java/com/thealgorithms/ciphers/RailFenceCipher.java @@ -0,0 +1,129 @@ +package com.thealgorithms.ciphers; + +import java.util.Arrays; + +/** + * The rail fence cipher (also called a zigzag cipher) is a classical type of transposition cipher. + * It derives its name from the manner in which encryption is performed, in analogy to a fence built with horizontal rails. + * https://en.wikipedia.org/wiki/Rail_fence_cipher + * @author https://github.com/Krounosity + */ + + + public class RailFenceCipher { + + // Encrypts the input string using the rail fence cipher method with the given number of rails. + public String encrypt(String str, int rails) { + + // Base case of single rail or rails are more than the number of characters in the string + if(rails == 1 || rails>=str.length()) return str; + + // Boolean flag to determine if the movement is downward or upward in the rail matrix. + boolean down = true; + // Create a 2D array to represent the rails (rows) and the length of the string (columns). + char[][] strRail = new char[rails][str.length()]; + + // Initialize all positions in the rail matrix with a placeholder character ('\n'). + for (int i = 0; i < rails; i++) + Arrays.fill(strRail[i], '\n'); + + int row = 0; // Start at the first row + int col = 0; // Start at the first column + + int i = 0; + + // Fill the rail matrix with characters from the string based on the rail pattern. + while (col < str.length()) { + // Change direction to down when at the first row. + if (row == 0) down = true; + // Change direction to up when at the last row. + else if (row == rails - 1) down = false; + + // Place the character in the current position of the rail matrix. + strRail[row][col] = str.charAt(i); + col++; // Move to the next column. + + // Move to the next row based on the direction. + if (down) row++; + else row--; + + i++; + } + + // Construct the encrypted string by reading characters row by row. + StringBuilder encryptedString = new StringBuilder(); + for (char[] chRow : strRail) { + for (char ch : chRow) { + if (ch != '\n') encryptedString.append(ch); + } + } + + return encryptedString.toString(); + } + + // Decrypts the input string using the rail fence cipher method with the given number of rails. + public String decrypt(String str, int rails) { + + // Base case of single rail or rails are more than the number of characters in the string + if(rails == 1 || rails>=str.length()) return str; + + // Boolean flag to determine if the movement is downward or upward in the rail matrix. + boolean down = true; + + // Create a 2D array to represent the rails (rows) and the length of the string (columns). + char[][] strRail = new char[rails][str.length()]; + + int row = 0; // Start at the first row + int col = 0; // Start at the first column + + // Mark the pattern on the rail matrix using '*'. + while (col < str.length()) { + + // Change direction to down when at the first row. + if (row == 0) down = true; + + // Change direction to up when at the last row. + else if (row == rails - 1) down = false; + + // Mark the current position in the rail matrix. + strRail[row][col] = '*'; + col++; // Move to the next column. + + // Move to the next row based on the direction. + if (down) row++; + else row--; + } + + int index = 0; // Index to track characters from the input string. + // Fill the rail matrix with characters from the input string based on the marked pattern. + for (int i = 0; i < rails; i++) { + for (int j = 0; j < str.length(); j++) { + if (strRail[i][j] == '*') { + strRail[i][j] = str.charAt(index++); + } + } + } + + // Construct the decrypted string by following the zigzag pattern. + StringBuilder decryptedString = new StringBuilder(); + row = 0; // Reset to the first row + col = 0; // Reset to the first column + + while (col < str.length()) { + // Change direction to down when at the first row. + if (row == 0) down = true; + // Change direction to up when at the last row. + else if (row == rails - 1) down = false; + + // Append the character from the rail matrix to the decrypted string. + decryptedString.append(strRail[row][col]); + col++; // Move to the next column. + + // Move to the next row based on the direction. + if (down) row++; + else row--; + } + + return decryptedString.toString(); + } +} diff --git a/src/test/java/com/thealgorithms/ciphers/AtbashTest.java b/src/test/java/com/thealgorithms/ciphers/AtbashTest.java new file mode 100644 index 000000000000..26812cf2b0d4 --- /dev/null +++ b/src/test/java/com/thealgorithms/ciphers/AtbashTest.java @@ -0,0 +1,28 @@ +package com.thealgorithms.ciphers; + +import static org.junit.jupiter.api.Assertions.assertEquals; + +import org.junit.jupiter.api.Test; + +public class AtbashTest { + + @Test + public void atbashEncrypt() { + AtbashCipher normalToEncrypt = new AtbashCipher("Hello World! 123, @cipher abcDEF ZYX 987 madam zzZ Palindrome!"); + String expectedText = "Svool Dliow! 123, @xrksvi zyxWVU ABC 987 nzwzn aaA Kzormwilnv!"; + + normalToEncrypt.setString(normalToEncrypt.convert()); + + assertEquals(expectedText, normalToEncrypt.getString()); + } + + @Test + public void atbashDecrypt() { + AtbashCipher encryptToNormal = new AtbashCipher("Svool Dliow! 123, @xrksvi zyxWVU ABC 987 nzwzn aaA Kzormwilnv!"); + String expectedText = "Hello World! 123, @cipher abcDEF ZYX 987 madam zzZ Palindrome!"; + + encryptToNormal.setString(encryptToNormal.convert()); + + assertEquals(expectedText, encryptToNormal.getString()); + } +} diff --git a/src/test/java/com/thealgorithms/ciphers/RailFenceTest.java b/src/test/java/com/thealgorithms/ciphers/RailFenceTest.java new file mode 100644 index 000000000000..2bfa704e3d0b --- /dev/null +++ b/src/test/java/com/thealgorithms/ciphers/RailFenceTest.java @@ -0,0 +1,62 @@ +package com.thealgorithms.ciphers; + +import static org.junit.jupiter.api.Assertions.assertEquals; + +import org.junit.jupiter.api.Test; + +public class RailFenceTest { + + @Test + void testEncryption() { + RailFenceCipher cipher = new RailFenceCipher(); + + String input = "We are discovered! Flee at once"; + int rails = 3; + String encrypted = cipher.encrypt(input, rails); + assertEquals("Wrivdlaneaedsoee!Fe toc cr e e", encrypted); + + String singleChar = "A"; + int singleRail = 2; + String encryptedSingleChar = cipher.encrypt(singleChar, singleRail); + assertEquals("A", encryptedSingleChar); + + String shortString = "Hello"; + int moreRails = 10; + String encryptedShortString = cipher.encrypt(shortString, moreRails); + assertEquals("Hello", encryptedShortString); + + String inputSingleRail = "Single line"; + int singleRailOnly = 1; + String encryptedSingleRail = cipher.encrypt(inputSingleRail, singleRailOnly); + assertEquals("Single line", encryptedSingleRail); + } + + @Test + void testDecryption() { + RailFenceCipher cipher = new RailFenceCipher(); + + // Scenario 1: Basic decryption with multiple rails + String encryptedInput = "Wrivdlaneaedsoee!Fe toc cr e e"; + int rails = 3; + String decrypted = cipher.decrypt(encryptedInput, rails); + assertEquals("We are discovered! Flee at once", decrypted); + + // Scenario 2: Single character string decryption + String encryptedSingleChar = "A"; + int singleRail = 2; // More than 1 rail + String decryptedSingleChar = cipher.decrypt(encryptedSingleChar, singleRail); + assertEquals("A", decryptedSingleChar); + + // Scenario 3: String length less than the number of rails + String encryptedShortString = "Hello"; + int moreRails = 10; // More rails than characters + String decryptedShortString = cipher.decrypt(encryptedShortString, moreRails); + assertEquals("Hello", decryptedShortString); + + // Scenario 4: Single rail decryption (output should be the same as input) + String encryptedSingleRail = "Single line"; + int singleRailOnly = 1; + String decryptedSingleRail = cipher.decrypt(encryptedSingleRail, singleRailOnly); + assertEquals("Single line", decryptedSingleRail); + } +}