Task: Chaocipher
C: #include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define TRUE 1
#define FALSE 0

typedef int bool;
typedef enum { ENCRYPT, DECRYPT } cmode;

const char *l_alphabet = "HXUCZVAMDSLKPEFJRIGTWOBNYQ";
const char *r_alphabet = "PTLNBQDEOYSFAVZKGJRIHWXUMC";

void chao(const char *in, char *out, cmode mode, bool show_steps) {
    int i, j, index;
    char store;
    size_t len = strlen(in);
    char left[27], right[27], temp[27];
    strcpy(left, l_alphabet);
    strcpy(right, r_alphabet);
    temp[26] = '\0';

    for (i = 0; i < len; ++i ) {
        if (show_steps) printf("%s  %s\n", left, right);
        if (mode == ENCRYPT) {
            index = strchr(right, in[i]) - right;
            out[i] = left[index];
        }
        else {
            index = strchr(left, in[i]) - left;
            out[i] = right[index];
        }
        if (i == len - 1) break;

        

        for (j = index; j < 26; ++j) temp[j - index] = left[j];
        for (j = 0; j < index; ++j) temp[26 - index + j] = left[j];
        store = temp[1];
        for (j = 2; j < 14; ++j) temp[j - 1] = temp[j];
        temp[13] = store;
        strcpy(left, temp);

        

        for (j = index; j < 26; ++j) temp[j - index] = right[j];
        for (j = 0; j < index; ++j) temp[26 - index + j] = right[j];
        store = temp[0];
        for (j = 1; j < 26; ++j) temp[j - 1] = temp[j];
        temp[25] = store;
        store = temp[2];
        for (j = 3; j < 14; ++j) temp[j - 1] = temp[j];
        temp[13] = store;
        strcpy(right, temp);
    }
}

int main() {
    const char *plain_text = "WELLDONEISBETTERTHANWELLSAID";
    char *cipher_text = malloc(strlen(plain_text) + 1);
    char *plain_text2 = malloc(strlen(plain_text) + 1);
    printf("The original plaintext is : %s\n", plain_text);
    printf("\nThe left and right alphabets after each permutation"
           " during encryption are :\n\n");
    chao(plain_text, cipher_text, ENCRYPT, TRUE);
    printf("\nThe ciphertext is : %s\n", cipher_text);
    chao(cipher_text, plain_text2, DECRYPT, FALSE);
    printf("\nThe recovered plaintext is : %s\n", plain_text2);
    free(cipher_text);
    free(plain_text2);
    return 0;
}

Java: import java.util.Arrays;

public class Chaocipher {
    private enum Mode {
        ENCRYPT,
        DECRYPT
    }

    private static final String L_ALPHABET = "HXUCZVAMDSLKPEFJRIGTWOBNYQ";
    private static final String R_ALPHABET = "PTLNBQDEOYSFAVZKGJRIHWXUMC";

    private static int indexOf(char[] a, char c) {
        for (int i = 0; i < a.length; ++i) {
            if (a[i] == c) {
                return i;
            }
        }
        return -1;
    }

    private static String exec(String text, Mode mode) {
        return exec(text, mode, false);
    }

    private static String exec(String text, Mode mode, Boolean showSteps) {
        char[] left = L_ALPHABET.toCharArray();
        char[] right = R_ALPHABET.toCharArray();
        char[] eText = new char[text.length()];
        char[] temp = new char[26];

        for (int i = 0; i < text.length(); ++i) {
            if (showSteps) {
                System.out.printf("%s  %s\n", new String(left), new String(right));
            }
            int index;
            if (mode == Mode.ENCRYPT) {
                index = indexOf(right, text.charAt(i));
                eText[i] = left[index];
            } else {
                index = indexOf(left, text.charAt(i));
                eText[i] = right[index];
            }
            if (i == text.length() - 1) {
                break;
            }

            

            if (26 - index >= 0) System.arraycopy(left, index, temp, 0, 26 - index);
            System.arraycopy(left, 0, temp, 26 - index, index);
            char store = temp[1];
            System.arraycopy(temp, 2, temp, 1, 12);
            temp[13] = store;
            left = Arrays.copyOf(temp, temp.length);

            

            if (26 - index >= 0) System.arraycopy(right, index, temp, 0, 26 - index);
            System.arraycopy(right, 0, temp, 26 - index, index);
            store = temp[0];
            System.arraycopy(temp, 1, temp, 0, 25);
            temp[25] = store;
            store = temp[2];
            System.arraycopy(temp, 3, temp, 2, 11);
            temp[13] = store;
            right = Arrays.copyOf(temp, temp.length);
        }

        return new String(eText);
    }

    public static void main(String[] args) {
        String plainText = "WELLDONEISBETTERTHANWELLSAID";
        System.out.printf("The original plaintext is : %s\n", plainText);
        System.out.println("\nThe left and right alphabets after each permutation during encryption are:");
        String cipherText = exec(plainText, Mode.ENCRYPT, true);
        System.out.printf("\nThe cipher text is : %s\n", cipherText);
        String plainText2 = exec(cipherText, Mode.DECRYPT);
        System.out.printf("\nThe recovered plaintext is : %s\n", plainText2);
    }
}