Rail Fence Cipher Program in C and C++[Encryption & Decryption]

Here you will get rail fence cipher program in C and C++ for encryption and decryption.

It is a kind of transposition cipher which is also known as zigzag cipher. Below is an example.

Here Key = 3. For encryption we write the message diagonally in zigzag form in a matrix having total rows = key and total columns = message length. Then read the matrix row wise horizontally to get encrypted message.

Rail Fence Cipher Program in C

#include<stdio.h>
#include<string.h>

void encryptMsg(char msg[], int key){
    int msgLen = strlen(msg), i, j, k = -1, row = 0, col = 0;
    char railMatrix[key][msgLen];

    for(i = 0; i < key; ++i)
        for(j = 0; j < msgLen; ++j)
            railMatrix[i][j] = '\n';

    for(i = 0; i < msgLen; ++i){
        railMatrix[row][col++] = msg[i];

        if(row == 0 || row == key-1)
            k= k * (-1);

        row = row + k;
    }

    printf("\nEncrypted Message: ");

    for(i = 0; i < key; ++i)
        for(j = 0; j < msgLen; ++j)
            if(railMatrix[i][j] != '\n')
                printf("%c", railMatrix[i][j]);
}

void decryptMsg(char enMsg[], int key){
    int msgLen = strlen(enMsg), i, j, k = -1, row = 0, col = 0, m = 0;
    char railMatrix[key][msgLen];

    for(i = 0; i < key; ++i)
        for(j = 0; j < msgLen; ++j)
            railMatrix[i][j] = '\n';

    for(i = 0; i < msgLen; ++i){
        railMatrix[row][col++] = '*';

        if(row == 0 || row == key-1)
            k= k * (-1);

        row = row + k;
    }

    for(i = 0; i < key; ++i)
        for(j = 0; j < msgLen; ++j)
            if(railMatrix[i][j] == '*')
                railMatrix[i][j] = enMsg[m++];

    row = col = 0;
    k = -1;

    printf("\nDecrypted Message: ");

    for(i = 0; i < msgLen; ++i){
        printf("%c", railMatrix[row][col++]);

        if(row == 0 || row == key-1)
            k= k * (-1);

        row = row + k;
    }
}

int main(){
    char msg[] = "Hello World";
    char enMsg[] = "Horel ollWd";
    int key = 3;

    printf("Original Message: %s", msg);

    encryptMsg(msg, key);
    decryptMsg(enMsg, key);

    return 0;
}

Output

Original Message: Hello World
Encrypted Message: Horel ollWd
Decrypted Message: Hello World

Rail Fence Cipher Program in C++

#include<iostream>
#include<string.h>

using namespace std;

void encryptMsg(char msg[], int key){
    int msgLen = strlen(msg), i, j, k = -1, row = 0, col = 0;
    char railMatrix[key][msgLen];

    for(i = 0; i < key; ++i)
        for(j = 0; j < msgLen; ++j)
            railMatrix[i][j] = '\n';

    for(i = 0; i < msgLen; ++i){
        railMatrix[row][col++] = msg[i];

        if(row == 0 || row == key-1)
            k= k * (-1);

        row = row + k;
    }

    cout<<"\nEncrypted Message: ";

    for(i = 0; i < key; ++i)
        for(j = 0; j < msgLen; ++j)
            if(railMatrix[i][j] != '\n')
                cout<<railMatrix[i][j];
}

void decryptMsg(char enMsg[], int key){
    int msgLen = strlen(enMsg), i, j, k = -1, row = 0, col = 0, m = 0;
    char railMatrix[key][msgLen];

    for(i = 0; i < key; ++i)
        for(j = 0; j < msgLen; ++j)
            railMatrix[i][j] = '\n';

    for(i = 0; i < msgLen; ++i){
        railMatrix[row][col++] = '*';

        if(row == 0 || row == key-1)
            k= k * (-1);

        row = row + k;
    }

    for(i = 0; i < key; ++i)
        for(j = 0; j < msgLen; ++j)
            if(railMatrix[i][j] == '*')
                railMatrix[i][j] = enMsg[m++];

    row = col = 0;
    k = -1;

    cout<<"\nDecrypted Message: ";

    for(i = 0; i < msgLen; ++i){
        cout<<railMatrix[row][col++];

        if(row == 0 || row == key-1)
            k= k * (-1);

        row = row + k;
    }
}

int main(){
    char msg[] = "Hello World";
    char enMsg[] = "Horel ollWd";
    int key = 3;

    cout<<"Original Message: "<<msg;

    encryptMsg(msg, key);
    decryptMsg(enMsg, key);
    
    return 0;
}

Comment below if you have queries related to above rail fence cipher program in C and C++.