C++ Programming Code Examples
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C++ Program to Perform Cryptography Using Transposition Technique
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/* C++ Program to Perform Cryptography Using Transposition Technique
This is a C++ Program to implement transposition technique. In cryptography, a transposition cipher is a method of encryption by which the positions held by units of plaintext (which are commonly characters or groups of characters) are shifted according to a regular system, so that the ciphertext constitutes a permutation of the plaintext. That is, the order of the units is changed (the plaintext is reordered). Mathematically a bijective function is used on the characters' positions to encrypt and an inverse function to decrypt. */
#include<stdio.h>
#include<string.h>
void cipher(int i, int c);
int findMin();
void makeArray(int, int);
char arr[22][22], darr[22][22], emessage[111], retmessage[111], key[55];
char temp[55], temp2[55];
int k = 0;
int main()
{
char *message;
int i, j, klen, emlen, flag = 0;
int r, c, index, rows;
printf("Enter the key\n");
fflush(stdin);
gets(key);
printf("\nEnter message to be ciphered\n");
fflush(stdin);
gets(message);
strcpy(temp, key);
klen = strlen(key);
k = 0;
for (i = 0;; i++)
{
if (flag == 1)
break;
for (j = 0; key[j] != NULL; j++)
{
if (message[k] == NULL)
{
flag = 1;
arr[i][j] = '-';
}
else
{
arr[i][j] = message[k++];
}
}
}
r = i;
c = j;
for (i = 0; i < r; i++)
{
for (j = 0; j < c; j++)
{
printf("%c ", arr[i][j]);
}
printf("\n");
}
k = 0;
for (i = 0; i < klen; i++)
{
index = findMin();
cipher(index, r);
}
emessage[k] = '\0';
printf("\nEncrypted message is\n");
for (i = 0; emessage[i] != NULL; i++)
printf("%c", emessage[i]);
printf("\n\n");
//deciphering
emlen = strlen(emessage);
//emlen is length of encrypted message
strcpy(temp, key);
rows = emlen / klen;
//rows is no of row of the array to made from ciphered message
j = 0;
for (i = 0, k = 1; emessage[i] != NULL; i++, k++)
{
//printf("\nEmlen=%d",emlen);
temp2[j++] = emessage[i];
if ((k % rows) == 0)
{
temp2[j] = '\0';
index = findMin();
makeArray(index, rows);
j = 0;
}
}
printf("\nArray Retrieved is\n");
k = 0;
for (i = 0; i < r; i++)
{
for (j = 0; j < c; j++)
{
printf("%c ", darr[i][j]);
//retrieving message
retmessage[k++] = darr[i][j];
}
printf("\n");
}
retmessage[k] = '\0';
printf("\nMessage retrieved is\n");
for (i = 0; retmessage[i] != NULL; i++)
printf("%c", retmessage[i]);
return (0);
}
void cipher(int i, int r)
{
int j;
for (j = 0; j < r; j++)
{
{
emessage[k++] = arr[j][i];
}
}
// emessage[k]='\0';
}
void makeArray(int col, int row)
{
int i, j;
for (i = 0; i < row; i++)
{
darr[i][col] = temp2[i];
}
}
int findMin()
{
int i, j, min, index;
min = temp[0];
index = 0;
for (j = 0; temp[j] != NULL; j++)
{
if (temp[j] < min)
{
min = temp[j];
index = j;
}
}
temp[index] = 123;
return (index);
}
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