Multiplicative Cipher (C++)

Multiplicative Cipher : Encryption

#include<iostream.h>

#include<conio.h>

#include<string.h>

#include<ctype.h>

class MulCiph

{

  public:

  char str[100];

  int key;

  void getkey();

  void gettext();

  void convert();

};

void MulCiph :: gettext()

{

  cout<<"\nEnter the string: ";

  cin>>str;

}

void MulCiph :: getkey()

{

  cout<<"\nEnter the multiplicative cipher key: ";

  cin>>key;

}

void MulCiph :: convert()

{

  int h=strlen(str);

  for(int i=0;i<h;i++)

  {

    char c=(((toascii(str[i])-97)*key)%26)+97;

    cout<<str[i]<<"\t"<<((toascii(str[i])-97)*key)%26<<"\t"<<c<<endl;

  }

}

void main()

{

  clrscr();

  MulCiph a;

  a.gettext();

  a.getkey();

  a.convert();

  getch();

}

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Multiplicative Cipher: Decryption

#include<iostream.h>

#include<conio.h>

#include<string.h>

#include<ctype.h>

class AddCiph

{

  public:

  char str[100];

  int key;

  void getkey();

  void gettext();

  void convert();

  int inverse(int);

};

void AddCiph :: gettext()

{

  cout<<"\nEnter the string: ";

  cin>>str;

}

void AddCiph :: getkey()

{

  cout<<"\nEnter the multiplicative cipher key: ";

  cin>>key;

}

int AddCiph :: inverse(int key)

{

  int r1,r2,r,q,t1,t2,t;

  r1=26;r2=key;

  t1=0;t2=1;

  while(r2>0)

  {

    q=r1/r2;

    r=r1-q*r2;

    r1=r2;r2=r;

    t=t1-q*t2;

    t1=t2;t2=t;

  }

  if(r1==1)

  {

    if(t1<0)

      t1+=26;

    return t1;

  }

}

void AddCiph :: convert()

{

  int h=strlen(str);

  int inv=inverse(key);

  for(int i=0;i<h;i++)

  {

    int dkey=(((toascii(str[i])-97)*inv))%26;

    char ch=dkey+97;

    cout<<str[i]<<"\t"<<dkey<<"\t"<<ch<<endl;

  }

}

void main()

{

  clrscr();

  AddCiph a;

  a.gettext();

  a.getkey();

  a.convert();

  getch();

}

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