BaconianCipher.java

packagecom.thealgorithms.ciphers;

importjava.util.HashMap;
importjava.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
 */
publicclassBaconianCipher {

privatestaticfinalMap<Character, String> BACONIAN_MAP = newHashMap<>();
privatestaticfinalMap<String, Character> REVERSE_BACONIAN_MAP = newHashMap<>();

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"};
charletter = 'A';
for (Stringcode : 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.
 */
publicStringencrypt(Stringplaintext) {
StringBuilderciphertext = newStringBuilder();
plaintext = plaintext.toUpperCase().replaceAll("[^A-Z]", ""); // Remove non-letter characters

for (charletter : plaintext.toCharArray()) {
ciphertext.append(BACONIAN_MAP.get(letter));
 }

returnciphertext.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.
 */
publicStringdecrypt(Stringciphertext) {
StringBuilderplaintext = newStringBuilder();

for (inti = 0; i < ciphertext.length(); i += 5) {
Stringcode = ciphertext.substring(i, i + 5);
if (REVERSE_BACONIAN_MAP.containsKey(code)) {
plaintext.append(REVERSE_BACONIAN_MAP.get(code));
 } else {
thrownewIllegalArgumentException("Invalid Baconian code: " + code);
 }
 }

returnplaintext.toString();
 }
}