diff --git a/src/main/java/com/thealgorithms/ciphers/BaconianCipher.java b/src/main/java/com/thealgorithms/ciphers/BaconianCipher.java new file mode 100644 index 000000000000..16dfd6e674af --- /dev/null +++ b/src/main/java/com/thealgorithms/ciphers/BaconianCipher.java @@ -0,0 +1,71 @@ +package com.thealgorithms.ciphers; + +import java.util.HashMap; +import java.util.Map; + +/** + * The Baconian Cipher is a substitution cipher where each letter is represented + * by a group of five binary digits (A's and B's). It can also be used to hide + * messages within other texts, making it a simple form of steganography. + * https://en.wikipedia.org/wiki/Bacon%27s_cipher + * + * @author Bennybebo + */ +public class BaconianCipher { + + private static final Map BACONIAN_MAP = new HashMap<>(); + private static final Map REVERSE_BACONIAN_MAP = new HashMap<>(); + + static { + // Initialize the Baconian cipher mappings + String[] baconianAlphabet = {"AAAAA", "AAAAB", "AAABA", "AAABB", "AABAA", "AABAB", "AABBA", "AABBB", "ABAAA", "ABAAB", "ABABA", "ABABB", "ABBAA", "ABBAB", "ABBBA", "ABBBB", "BAAAA", "BAAAB", "BAABA", "BAABB", "BABAA", "BABAB", "BABBA", "BABBB", "BBAAA", "BBAAB"}; + char letter = 'A'; + for (String code : baconianAlphabet) { + BACONIAN_MAP.put(letter, code); + REVERSE_BACONIAN_MAP.put(code, letter); + letter++; + } + + // Handle I/J as the same letter + BACONIAN_MAP.put('I', BACONIAN_MAP.get('J')); + REVERSE_BACONIAN_MAP.put(BACONIAN_MAP.get('I'), 'I'); + } + + /** + * Encrypts the given plaintext using the Baconian cipher. + * + * @param plaintext The plaintext message to encrypt. + * @return The ciphertext as a binary (A/B) sequence. + */ + public String encrypt(String plaintext) { + StringBuilder ciphertext = new StringBuilder(); + plaintext = plaintext.toUpperCase().replaceAll("[^A-Z]", ""); // Remove non-letter characters + + for (char letter : plaintext.toCharArray()) { + ciphertext.append(BACONIAN_MAP.get(letter)); + } + + return ciphertext.toString(); + } + + /** + * Decrypts the given ciphertext encoded in binary (A/B) format using the Baconian cipher. + * + * @param ciphertext The ciphertext to decrypt. + * @return The decrypted plaintext message. + */ + public String decrypt(String ciphertext) { + StringBuilder plaintext = new StringBuilder(); + + for (int i = 0; i < ciphertext.length(); i += 5) { + String code = ciphertext.substring(i, i + 5); + if (REVERSE_BACONIAN_MAP.containsKey(code)) { + plaintext.append(REVERSE_BACONIAN_MAP.get(code)); + } else { + throw new IllegalArgumentException("Invalid Baconian code: " + code); + } + } + + return plaintext.toString(); + } +} diff --git a/src/test/java/com/thealgorithms/ciphers/BaconianCipherTest.java b/src/test/java/com/thealgorithms/ciphers/BaconianCipherTest.java new file mode 100644 index 000000000000..bb1ae5a7e4c2 --- /dev/null +++ b/src/test/java/com/thealgorithms/ciphers/BaconianCipherTest.java @@ -0,0 +1,34 @@ +package com.thealgorithms.ciphers; + +import static org.junit.jupiter.api.Assertions.assertEquals; + +import org.junit.jupiter.api.Test; + +class BaconianCipherTest { + + BaconianCipher baconianCipher = new BaconianCipher(); + + @Test + void baconianCipherEncryptTest() { + // given + String plaintext = "MEET AT DAWN"; + + // when + String cipherText = baconianCipher.encrypt(plaintext); + + // then + assertEquals("ABBAAAABAAAABAABAABBAAAAABAABBAAABBAAAAABABBAABBAB", cipherText); + } + + @Test + void baconianCipherDecryptTest() { + // given + String ciphertext = "ABBAAAABAAAABAABAABBAAAAABAABBAAABBAAAAABABBAABBAB"; + + // when + String plainText = baconianCipher.decrypt(ciphertext); + + // then + assertEquals("MEETATDAWN", plainText); + } +}