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;
}











Ada: with Ada.Text_IO; use Ada.Text_IO;

procedure chao_slices is
   type iMode is (Encrypt, Decrypt);

   L_Alphabet : String := "HXUCZVAMDSLKPEFJRIGTWOBNYQ";
   R_Alphabet : String := "PTLNBQDEOYSFAVZKGJRIHWXUMC";
   plaintext  : String := "WELLDONEISBETTERTHANWELLSAID";
   ciphertext : String (1 .. plaintext'length);
   plaintext2 : String (1 .. plaintext'length);
   offset     : Natural;

   function IndexOf (Source : String; Value : Character) return Positive is
      Result : Positive;

   begin
      for I in Source'Range loop
         if Source (I) = Value then
            Result := I;
            exit;
         end if;
      end loop;
      return Result;
   end IndexOf;

   function Exec
     (Text : String; mode : iMode; showsteps : Boolean := False) return String
   is
      etext : String (Text'First .. Text'Last);
      temp  : String (1 .. 26);
      index : Positive;
      store : Character;
      left  : String := L_Alphabet;
      right : String := R_Alphabet;
   begin
      for I in Text'Range loop
         if showsteps then
            Put_Line (left & "  " & right);
         end if;

         if mode = Encrypt then
            index     := IndexOf (Source => right, Value => Text (I));
            etext (I) := left (index);
         else
            index     := IndexOf (Source => left, Value => Text (I));
            etext (I) := right (index);
         end if;

         exit when I = Text'Last;

         
         
         

         if index > 1 then
            offset                 := 26 - index;
            temp (1 .. offset + 1) := left (index .. index + offset);

            temp (offset + 2 .. 26) := left (1 .. index - 1);
            store                   := temp (2);

            temp (2 .. 13) := temp (3 .. 14);
            temp (14)      := store;
            left           := temp;

            
            
            

            temp (1 .. offset + 1) := right (index .. index + offset);

            temp (offset + 2 .. 26) := right (1 .. index - 1);
            store                   := temp (1);

            temp (1 .. 25) := temp (2 .. 26);
            temp (26)      := store;
            store          := temp (3);

            temp (3 .. 13) := temp (4 .. 14);
            temp (14)      := store;
            right          := temp;
         end if;

      end loop;

      return etext;

   end Exec;
begin
   Put_Line ("The original text is : " & plaintext);
   New_Line;
   Put_Line
     ("The left and right alphabets after each permutation during encryption are:");
   New_Line;
   ciphertext := Exec (plaintext, Encrypt, True);
   New_Line;
   Put_Line ("The ciphertext is : " & ciphertext);
   plaintext2 := Exec (ciphertext, Decrypt);
   New_Line;
   Put_Line ("The recovered plaintext is : " & plaintext2);
end chao_slices;