C++ Programming Code Examples
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Program to Encode a Message Using Playfair Cipher
/* Program to Encode a Message Using Playfair Cipher
This C++ program encodes any message using the technique of traditional playfair cipher. Input is not case sensitive and works only for characters from 'a' to 'z' and 'A' to 'Z'. White spaces are ignored. */
#include<iostream>
#include<vector>
using namespace std;
void get_pos(char, int&, int&);
void same_row(int, vector<char>&, int, int);
void same_column(int, vector<char>&, int, int);
void diff_col_row(int, int, vector<char>&, int, int);
void encode(vector<char>, int);
void get_input(vector<char>&);
void convert_string(vector<char>&, vector<char>&);
const char encoder[5][5]={{'A','B','C','D','E'},
{'F','G','H','I','K'},
{'L','M','N','O','P'},
{'Q','R','S','T','U'},
{'V','W','X','Y','Z'}};
void get_pos(char p, int& r, int& c)
{
if (p < 'J')
{
r = (p - 65) / 5;
c = (p - 65) % 5;
}
else if (p > 'J')
{
r = (p - 66) / 5;
c = (p - 66) % 5;
}
return;
}
void same_row(int r, vector<char>& code, int c1, int c2)
{
code.push_back(encoder[r][(c1 + 1) % 5]);
code.push_back(encoder[r][(c2 + 1) % 5]);
return;
}
void same_column(int c, vector<char>& code, int r1, int r2)
{
code.push_back(encoder[(r1 + 1) % 5][c]);
code.push_back(encoder[(r2 + 1) % 5][c]);
return;
}
void diff_col_row(int r1, int c1, vector<char>& code, int r2, int c2)
{
code.push_back(encoder[r1][c2]);
code.push_back(encoder[r2][c1]);
return;
}
void encode(vector<char> msgx, int len)
{
vector<char> code;
int i = 0, j = 0;
int r1, c1, r2, c2;
while (i < len)
{
get_pos(msgx[i], r1, c1);
i++;
get_pos(msgx[i], r2, c2);
if (r1 == r2)
{
same_row(r1, code, c1, c2);
}
else if (c1 == c2)
{
same_column(c1, code, r1, r2);
}
else
{
diff_col_row(r1, c1, code, r2, c2);
}
i++;
}
cout<<"\nCODE: ";
for (j = 0;j < code.size();j++)
{
cout<<code[j];
}
return;
}
void get_input(vector<char>& a)
{
char c;
while (1)
{
c = getchar();
if (c >= 97 && c <= 122)
c- =32;
if (c == '\n')
break;
else if (c==' ')
continue;
else if (c == 'J')
a.push_back('I');
a.push_back(c);
}
return;
}
void convert_string(vector<char>& msg, vector<char>& msgx)
{
int i, j;
i = j = 0;
while (i < msg.size())
{
msgx.push_back(msg[i]);
i++;
if (i == msg.size())
{
msgx.push_back('X');
break;
}
if (msg[i] == msgx[j])
{
msgx.push_back('X');
j++;
}
else if(msg[i] != msgx[j])
{
j++;
msgx.push_back(msg[i]);
i+ = 1;
}
j++;
}
}
int main()
{
vector<char> msg;
vector<char> msgx;
int i, j;
cout<<"Enter Message to Encrypt:";
get_input(msg);
convert_string(msg, msgx);
int len = msgx.size();
/*
cout<<"\n\n";
for (i = 0;i < len;i++)
cout<<msgx[i];
*///this is the string after making pairs of 2
encode(msgx, len);
return 0;
}
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