This is only the key generation part of S-DES.

S-DES Key Generation.cpp

/*
Md Tahmid Hasan
CSE, BSMRSTU
tahmidhasan3003
*/

#include<bits/stdc++.h>
using namespace std;

int p10[10]= {3,5,2,7,4,10,1,9,8,6}, p8[8]= {6,3,7,4,8,5,10,9};

void showPTable(int x)
{
    cout<<"Your P"<<x<<" permutation table is\t: ";
    if(x == 8)
        for(int i=0; i<x; i++)
            cout<<p8[i]<<" ";
    else if(x == 10)
        for(int i=0; i<x; i++)
            cout<<p10[i]<<" ";
    cout<<endl<<endl;
}

string doP8(string inputText)
{
    string outputText;
    for(int i=0; i<8; i++)
        outputText += inputText[p8[i]-1];

    cout<<"After P8 applying\t: "<<outputText<<endl;
    return outputText;
}

string doP10(string inputText)
{
    string outputText;
    for(int i=0; i<10; i++)
        outputText += inputText[p10[i]-1];

    cout<<"After P10 applying\t: "<<outputText<<endl<<endl;
    return outputText;
}

string doLS1(string inputText)
{
    string outputText;
    for(int i=0; i<inputText.length(); i++)
    {
        switch (i)
        {
        case 4:
            outputText += inputText[0];
            break;
        case 9:
            outputText += inputText[5];
            break;
        default:
            outputText += inputText[i+1];
        }
    }
    cout<<"After LS-1 applying\t: "<<outputText<<endl;
    return outputText;
}

string doLS2(string inputText)
{
    string outputText;
    for(int i=0; i<inputText.length(); i++)
    {
        switch (i)
        {
        case 3:
            outputText += inputText[0];
            break;
        case 4:
            outputText += inputText[1];
            break;
        case 8:
            outputText += inputText[5];
            break;
        case 9:
            outputText += inputText[6];
            break;
        default:
            outputText += inputText[i+2];
        }
    }
    cout<<"After LS-2 applying\t: "<<outputText<<endl;
    return outputText;
}

int main()
{
    string inputKey, key1, key2, temp, ls1, ls2;

    cout<<"Enter 10 bits input key:"<<endl;
    cin>>inputKey;

    while(inputKey.length() != 10)
    {
        cout<<"Please enter 10 bits input key:"<<endl;
        cin>>inputKey;
    }

    cout<<endl;
    showPTable(8);
    showPTable(10);

    temp = doP10(inputKey);

    ls1 = doLS1(temp);
    key1 = doP8(ls1);
    cout<<"Key 1\t\t\t: "<<key1<<endl<<endl;

    ls2 = doLS2(ls1);
    key2 = doP8(ls2);
    cout<<"Key 2\t\t\t: "<<key2<<endl;

    return 0;
}