Columnar Transposition Cipher Encryption in C++

//columnar_transposition
#include <iostream>
#include <cstdio>
#include <string>
#include <cstdlib>
#include <cctype>
#include <map>
using namespace std;
#define siz 100
char as[siz][siz];
int a[siz];
map <int, int> mp;
map <int, int>::iterator it;
int main()
{
    string plainText1, plainText, key, cipherText;
    freopen("input.txt", "r", stdin);
    while(getline(cin, plainText1) && getline(cin, key)) {

        cout << "Plain Text: " << plainText1 <<endl;
        cout << "Key: " << key <<endl;

        for(int i=0; i<key.size(); i++)
            mp[(key[i]-'A')] = i;

        for(int i=0; i<plainText1.size(); i++)
            if(isalpha(plainText1[i]))
                plainText += plainText1[i];

        int k = 0, row = 0;
        for(int i=0; ; i++){
            for(int j=0; j<key.size(); j++) {
                if(k >= plainText.size()) {
                    as[i][j] = rand()%26 + 'A';
                } else {
                    as[i][j] = plainText[k];
                }
                k++;
            }
            row++;
            if(k >= plainText.size()) break;
        }
        puts("Grid:");
        for(int i=0; i<row; i++){
            for(int j=0; j<key.size(); j++) {
                cout<<as[i][j]<<" ";
            }
            puts("");
        }


        for(it = mp.begin(); it != mp.end(); it++) {
            for(int i=0; i<row; i++){
                cipherText += as[i][(*it).second];
            }
            cipherText += " ";
        }

        cout<<"Cipher Text: "<<cipherText<<endl;
    }
    return 0;
}

Vigenere Cipher Encryption in C++

//Vigenere Cipher
#include <iostream>
#include <cstdio>
#include <string>
#include <cctype>
using namespace std;
#define siz 100
int P[siz], K[siz], C[siz];

int main()
{
    string plainText, key, cipherText;
    //freopen("input.txt", "r", stdin);
    while(getline(cin, plainText) && getline(cin, key)){
        cout << "Plain Text: " << plainText << endl;
        cout << "Key: " << key << endl;
        cout << "Cipher Text: ";
        int len = key.size();
        int j = 0;
        for(int i=0; i<plainText.size(); i++){
            if(isalpha(plainText[i])){
                P[i] = plainText[i] - 'a';
                K[j] = tolower(key[j % len]) - 'a';
                C[j] = (P[i] + K[j]) % 26;
                cout<<(char)toupper(C[j] + 'a')<<" ";
                j++;
            }
        }
        puts("");
    }
    return 0;
}

Playfair Cipher Encryption in C++

//playfair_cipher
#include <iostream>
#include <string>
#include <cstdio>
#include <cctype>
#include <map>
#include <utility>
using namespace std;
#define siz 5
map <char, int> mp;
pair<int, int> p1;
pair<int, int> p2;
map < char, pair<int, int> > pa;
char a[siz][siz], res[siz][siz];
string as="ABCDEFGHIJKLMNOPQRSTUVWXYZ";

bool ischar(char c){
    if((c>='a' && c<='z') || (c>='A' && c<='Z'))
        return true;
    return false;
}

int main()
{
    string key, message, msg;
    //freopen("input.txt", "r", stdin);
    while(getline(cin, key)){
        int k = 0, l = 0;
        int len = key.size();
        for(int i=0;i<len;i++){
            if(ischar(key[i])) {
                if(mp[toupper(key[i])] == 0) {
                    a[k][l] = toupper(key[i]);
                    pa.insert(make_pair(toupper(key[i]), make_pair(k, l)));
                    mp[toupper(key[i])] = 1;
                    l++;
                }

                if(l==5) {
                    k++;
                    l = 0;
                }
            }
        }
        //mp['J'] = 1;

        for(int i=0; i<as.size();i++){
            if((toupper(as[i])=='I'||toupper(as[i])=='J') && (mp['I'] == 1||mp['J'] == 1))
                continue;
            if(mp[toupper(as[i])] == 1)
                continue;
            else {
                a[k][l] = toupper(as[i]);
                pa.insert(make_pair(toupper(as[i]), make_pair(k, l)));
                l++;
            }

            if(l==5) {
                k++;
                l = 0;
            }
        }

        //printing the grid
        for(int i=0; i<5; i++) {
            for(int j=0; j<5; j++) {
                if(j) cout<< " ";
                cout << a[i][j];
                res[i][j]='0';
            }
            puts("");
        }

        //get the message
        getline(cin, msg);
        cout<<msg<<endl;

        for(int i=0; i<msg.size(); i++)
            if(ischar(msg[i]))
                message += msg[i];

        for(int i=0; i<message.size()-1; i++) {
            char x,y;

            if(message[i] != message[i+1]) {
                x = toupper(message[i]);
                y = toupper(message[i+1]);

                p1 = pa.find(x)->second;
                p2 = pa.find(y)->second;
                i += 1;
            } else {
                x = toupper(message[i]);
                y = 'X';
                p1 = pa.find(x)->second;
                p2 = pa.find(y)->second;

            }

            //columns are same
                if(p1.second == p2.second) {
                    if(p1.first+1 < 5)
                        cout << a[p1.first + 1][p1.second];
                    else
                        cout << a[0][p1.second];

                    if(p2.first+1 < 5)
                        cout << a[p2.first + 1][p2.second];
                    else
                        cout << a[0][p2.second];
                } else if(p1.first == p2.first) { //rows are same
                    if(p1.second+1 < 5)
                        cout << a[p1.first][p1.second + 1];
                    else
                        cout << a[p1.first][0];

                    if(p2.second+1 < 5)
                        cout << a[p2.first][p2.second + 1];
                    else
                        cout << a[p2.first][0];
                } else {
                    cout    << a[p1.first][p2.second]
                            << a[p2.first][p1.second];
                }
                printf(" ");
        }

        //clearing
        mp.clear();
    }
    return 0;
}

Auto Key Cipher Encryption

//auto_key_cipher
#include <iostream>
#include <cstdio>
#include <string>
using namespace std;
#define siz 100
int p[siz], c[siz], k[siz];

int main()
{
    int key, x;
    string plainText, cipherText;
    freopen("input.txt", "r", stdin);
    while(cin>>plainText>>key){
        //encryption
        int len = plainText.size();
        for(int i=0; i<len; i++){
            p[i] = plainText[i] - 'a';
            if(i==0) k[i] = key;
            else k[i] = p[i-1];
            c[i] = (p[i] + k[i]) % 26;
            cipherText += c[i] + 'A';
        }
        cout<<"Cipher Text: "<<cipherText<<endl;
    }
    return 0;
}

Affine Cipher Encryption and Decryption

//Affine Cipher
#include <iostream>
#include <cstdio>
#include <string>
using namespace std;

int multiplicative_inverse(int, int);

int main()
{
    int key_1, key_2, x;
    string plainText, cipherText;
    while(cin>>plainText>>key_1>>key_2){
        //encryption
        cipherText = "";
        int len = plainText.size();
        for(int i=0; i<len; i++){
            x = ((plainText[i] - 'a') * key_1 + key_2) % 26;
            cipherText += x + 'A';
        }
        cout<<"Cipher Text: "<<cipherText<<endl;

        //decryption
        plainText = "";
        int keyInverse = multiplicative_inverse(26, key_1);
        cout<<"Multiplicative Inverse: "<<keyInverse<<endl;
        for(int i=0; i<len; i++){
            x = ((cipherText[i] - 'A' - key_2) * keyInverse) % 26;
            if(x < 0) x += 26;
            plainText += x + 'a';
        }
        cout<<"Plain Text: "<<plainText<<endl;

    }
    return 0;
}

int multiplicative_inverse(int x, int y){
    int q, r, r1, r2, t1, t2, t;
    r1 = x;
    r2 = y;
    t1 = 0;
    t2 = 1;
    while(r2 != 0){
        q = r1 / r2;
        r = r1 % r2;
        t = t1 - t2*q;
        r1 = r2;
        r2 = r;
        t1 = t2;
        t2 = t;
    }
    if(r1 != 1) return 0;
    else {
        if(t1<0) return t1+x;
        else return t1;
    }
}

Rail Fence Cipher

//rail_fence_cipher
#include <iostream>
#include <string>
#include <cstdio>
#include <cmath>
using namespace std;

int main()
{
    int j,k;
    string as, bs, cipherText;
    //freopen("input.txt","r",stdin);
    while(cin>>cipherText){
        int len = cipherText.size();
        int flag = 0;
        for(int i=0; i < len; i++){
            if(i == ceil(len / 2.0)) flag = 1;
            if(flag == 0) as += cipherText[i];
            else bs += cipherText[i];
        }
        j = k = 0;
        cout<<"Cipher Text: "<<cipherText<<endl;
        cout<<"Plain Text: ";
        for(int i=0; i < len; i++){
            if(i % 2 == 0) cout<<as[k++];
            else cout<<bs[j++];
        }
        puts("");
        //clearing
        as.clear();
        bs.clear();
    }
    return 0;
}

Simple Multiplicative Cipher

//Multiplicative Cipher
#include <iostream>
#include <cstdio>
#include <cctype>
using namespace std;

int multiplicative_inverse(int x, int y){
    int q, r, r1, r2, t1, t2, t;
    r1 = x;
    r2 = y;
    t1 = 0;
    t2 = 1;
    while(r2 != 0){
        q = r1 / r2;
        r = r1 % r2;
        t = t1 - t2*q;
        r1 = r2;
        r2 = r;
        t1 = t2;
        t2 = t;
    }
    if(r1 != 1) return 0;
    else {
        if(t1<0) return t1+x;
        else return t1;
    }
}

int main()
{
    int key;
    string plainText, cipherText;
    freopen("input.txt","r",stdin);
    while(cin>>key>>plainText){
        //encryption
        cipherText = "";
        int len = plainText.size();
        for(int i=0; i<len; i++){
            int x = ((plainText[i] - 'a') * key) % 26;
            cipherText += toupper(x + 'a');
        }
        cout<<"Key: "<<key<<endl;
        cout<<"Cipher Text: "<<cipherText<<endl;
        //decrption
        plainText = "";
        int keyInverse = multiplicative_inverse(26, key);
        cout<<"Multiplicative Inverse: "<<keyInverse<<endl;
        for(int i=0; i<len; i++){
            int x = ((cipherText[i] - 'A') * keyInverse ) % 26;
            plainText += (x + 'a');
        }
        cout<<"Plain Text: "<<plainText<<endl;
    }
    return 0;
}