PHP Code:
#include <stdlib.h>
#include <stdio.h>
#include<string.h>
void playfair_encipher(char *key, const char *plaintext, char *ciphertext);
void playfair_decipher(char *key, const char *ciphertext, char *plaintext);
void prepare_for_playfair(char *originaltext, char *plaintext);
int main(int argc, char *argv[]){
/************************!
/*
printf("Please enter Text that want to encrypt = ");
scanf("%c\n", &Text);
printf("data = %c\n", Text);
char *originaltext = Text;
*/
/* the string to encipher / decipher (want to modified to interactive code!)*/
char *originaltext = "Defend the east wall of the castle.";
//***********************!
/* allocate some space for results of enciphering/deciphering */
char *plaintext = malloc(strlen(originaltext)+2);
char *ciphertext = malloc(strlen(originaltext)+2);
char *result = malloc(strlen(originaltext)+2);
/* we have to remove punctuation, spacing etc. and make the string an
even number of bytes long */
prepare_for_playfair(originaltext,plaintext);
//**************************!
/* the following lines do all the enciphering and deciphering */
//hope this can be user input too
playfair_encipher("cdefghiklmnopqrstuvwxyzab", plaintext,ciphertext);
playfair_decipher("cdefghiklmnopqrstuvwxyzab", ciphertext,result);
//**************************!
/* print our results */
printf("-->original: %s\n-->cleaned: %s\n-->ciphertext: %s\n-->plaintext: %s\n",
originaltext,plaintext,ciphertext,result);
free(plaintext);
free(ciphertext);
free(result);
system("PAUSE");
return 0;
}
/*******************************************************************
void playfair_encipher(char *key, const char *plaintext, char *ciphertext)
- Uses playfair cipher to encipher some text.
- takes a key, string of plaintext, result returned in ciphertext.
- ciphertext should be an array the same size as plaintext.
- The key is a string containing each of the 26 letters in the alphabet.
*******************************************************************/
void playfair_encipher(char *key, const char *plaintext, char *ciphertext){
int i = 0, length = strlen(plaintext);
char a,b;
int a_ind, b_ind, a_row, b_row, a_col, b_col;
for(i = 0; i < length; i+=2){
a = tolower(plaintext[i]);
b = tolower(plaintext[i+1]);
a_ind = (int)strchr(key,a) - (int)key;
b_ind = (int)strchr(key,b) - (int)key;
a_row = a_ind / 5;
b_row = b_ind / 5;
a_col = a_ind % 5;
b_col = b_ind % 5;
if(a_row == b_row){
if(a_col == 4){
ciphertext[i] = key[a_ind - 4];
ciphertext[i+1] = key[b_ind + 1];
}else if(b_col == 4){
ciphertext[i] = key[a_ind + 1];
ciphertext[i+1] = key[b_ind - 4];
}else{
ciphertext[i] = key[a_ind + 1];
ciphertext[i+1] = key[b_ind + 1];
}
}else if(a_col == b_col){
if(a_row == 4){
ciphertext[i] = key[a_ind - 20];
ciphertext[i+1] = key[b_ind + 5];
}else if(b_row == 4){
ciphertext[i] = key[a_ind + 5];
ciphertext[i+1] = key[b_ind - 20];
}else{
ciphertext[i] = key[a_ind + 5];
ciphertext[i+1] = key[b_ind + 5];
}
}else{
ciphertext[i] = key[5*a_row + b_col];
ciphertext[i+1] = key[5*b_row + a_col];
}
}while (i < length);
ciphertext[length] = '\0';
}
/*******************************************************************
void playfair_decipher(char *key, const char *ciphertext, char *plaintext)
- Uses playfair cipher to decipher some text.
- takes a key, string of ciphertext, result returned in plaintext.
- plaintext should be an array the same size as ciphertext.
- The key is a string containing each of the 26 letters in the alphabet.
*******************************************************************/
void playfair_decipher(char *key, const char *ciphertext, char *plaintext){
int i, length = strlen(ciphertext);
char a,b;
int a_ind, b_ind, a_row, b_row, a_col, b_col;
for(i = 0; i < length; i+=2){
a = tolower(ciphertext[i]);
b = tolower(ciphertext[i+1]);
a_ind = (int)strchr(key,a) - (int)key;
b_ind = (int)strchr(key,b) - (int)key;
a_row = a_ind / 5;
b_row = b_ind / 5;
a_col = a_ind % 5;
b_col = b_ind % 5;
if(a_row == b_row){
if(a_col == 0){
plaintext[i] = key[a_ind + 4];
plaintext[i+1] = key[b_ind - 1];
}else if(b_col == 0){
plaintext[i] = key[a_ind - 1];
plaintext[i+1] = key[b_ind + 4];
}else{
plaintext[i] = key[a_ind - 1];
plaintext[i+1] = key[b_ind - 1];
}
}else if(a_col == b_col){
if(a_row == 0){
plaintext[i] = key[a_ind + 20];
plaintext[i+1] = key[b_ind - 5];
}else if(b_row == 0){
plaintext[i] = key[a_ind - 5];
plaintext[i+1] = key[b_ind + 20];
}else{
plaintext[i] = key[a_ind - 5];
plaintext[i+1] = key[b_ind - 5];
}
}else{
plaintext[i] = key[5*a_row + b_col];
plaintext[i+1] = key[5*b_row + a_col];
}
}
plaintext[length] = '\0'; /* Null terminate */
}
/************************************************************************
void prepare_for_playfair(char *originaltext, char *plaintext)
- removes all characters that are not letters. i.e. all numbers, punctuation,
spaces etc. are removed (uppercase is also converted to lowercase). If the length
of the string is odd, an x is appended to make it an even length
- playfair can only encrypt even length strings.
- If you want numbers, punctuation etc. you must spell it out e.g.
'stop' for period, 'one', 'two' etc.
**************************************************************************/
void prepare_for_playfair(char *originaltext, char *plaintext){
int i, j, length = strlen(originaltext);
for(i = 0, j = 0; i < length; i++, j++){
while(!isalpha(originaltext[i])) i++;
if(i >= length) break;
plaintext[j] = tolower(originaltext[i]);
}
/* if the string is an even length, leave it */
if (j % 2 == 0) plaintext[j] = '\0';
/* else append an 'x' */
else {
plaintext[j] = 'x';
plaintext[j+1] = '\0';
}
}
Adv Reply
Originally Posted by AlexenderReez
Bookmarks