//**************************************
//     
// Name: Play Fair Cipher
// Description:Used to Encrypt Input Str
//     ing
// By: Girish979
//
// Inputs:A String
//
// Returns:Nothing
//
// Side Effects:Nothing
//
//This code is copyrighted and has// limited warranties.Please see http://
//     www.Planet-Source-Code.com/vb/scripts/Sh
//     owCode.asp?txtCodeId=12537&lngWId=3//for details.//**************************************
//     

#include <stdio.h>
#define siz 5
void encrypt(int *i, int *j)


    {
    	(*i)++,(*j)++;
    	if((*i)==siz) *i=0;
    	else if((*j)==siz) *j=0;
}
void playfair(char ch1,char ch2, char mat[siz][siz])


    {
    	int j,m,n,p,q,c,k;
    	for(j=0,c=0;(c<2)||(j<siz);j++)
    		for(k=0;k<siz;k++)
    			if(mat[j][k] == ch1)
    				m=j,n=k,c++;
    			else if(mat[j][k] == ch2)
    				p=j,q=k,c++;
    	if(m==p)
    		encrypt(&n,&q);
    	else if(n==q)
    		encrypt(&m,&p);
    	else
    		n+=q,q=n-q,n-=q;
    	printf("%c%c",mat[m][n],mat[p][q]);
}
void main()


    {
    char mat[siz][siz],key[10],str[25]={0};
    int m,n,i,j;
    char temp;
    printf("Enter Key String:");
    gets(key);
    m=n=0;
    for(i=0;key[i]!='\0';i++)


        {
        		for(j=0;j<i;j++)
        			if(key[j] == key[i]) break;
        		if(key[i]=='j') key[i]='i';
        		if(j>=i)


            		{
            			mat[m][n++] = key[i];
            			if(n==siz)
            				n=0,m++;
            		}
        }
        for(i=97;i<=122;i++)


            {
            		for(j=0;key[j]!='\0';j++)
            			if(key[j] == i)
            			 break;
            			else if(i=='j')
            				break;
            	 if(key[j]=='\0')


                	 {
                		mat[m][n++] = i;
                		if(n==siz) n=0,m++;
                	 }
                	}
                	printf("Enter input String:");
                	gets(str);
                	printf("\n\nMatrix :\n");
                	for(i=0;i<siz;i++)


                    	{
                    		for(j=0;j<siz;j++)
                    			printf("%c\t",mat[i][j]);
                    		printf("\n");
                    	}
                    	printf("\n\nEntered text :%s\nCipher Text :",str);
                    	for(i=0;str[i]!='\0';i++)


                        	{
                        		temp = str[i++];
                        		if(temp == 'j') temp='i';
                        		if(str[i]=='\0')
                        			playfair(temp,'x',mat);
                        		else


                            		{
                            			if(str[i]=='j') str[i]='i';
                            			if(temp == str[i])


                                			{
                                				playfair(temp,'x',mat);
                                				i--;
                                			}
                                			else
                                				playfair(temp,str[i],mat);
                                		}
                                	}
                            }