Caesar::Caesar(QObject *parent) :

    QObject(parent)

{

}

// fungsi enkripsi penyandian caesar

// texterang : huruf abjad yang akan di enkripsi (tipe:char)

// kunci : kunci yang digunakan enkripsi (tipe:integer)

// panjangtexterang : jumlah huruf abjad yang akan dilakukan enkripsi

void Caesar::enkripsiCaesar(char textterang[], int kunci, int panjangtextterang)

{

    for (int i=0; i < panjangtextterang; i++)

        {

            if (textterang[i] >= 'A' && textterang[i] <= 'Z')

            {

                textterang[i] = (char)(((textterang[i] + kunci - 'A' + 26) % 26) + 'A');

            }

            else if (textterang[i] >= 'a' && textterang[i] <= 'z')

            {

                textterang[i] = (char)(((textterang[i] + kunci - 'a' + 26) % 26) + 'a');

            }

        }

}

//fungsi dekripsi penyandian caesar

void Caesar::dekripsiCaesar(char textterang[], int kunci, int panjangtextterang)

{

    for (int i=0; i < panjangtextterang; i++)

        {

            if (textterang[i] >= 'A' && textterang[i] <= 'Z')

            {

                textterang[i] = (char)(((textterang[i] - kunci - 'A' + 26) % 26) + 'A');

            }

            else if (textterang[i] >= 'a' && textterang[i] <= 'z')

            {

                textterang[i] = (char)(((textterang[i] - kunci - 'a' + 26) % 26) + 'a');

            }

        }

}

caesar.h

#ifndef CAESAR_H
#define CAESAR_H


#include 

class Caesar : public QObject
{
    Q_OBJECT
public:
    explicit Caesar(QObject *parent = 0);
    void enkripsiCaesar(char textterang[100], int kunci, int panjangtextterang);
    void dekripsiCaesar(char textterang[100], int kunci, int panjangtextterang);
signals:  
public slots:    
};

#endif // CAESAR_H