C++ Programming Code Examples C++ > Strings Code Examples C++ Program to Perform Cryptography Using Transposition Technique 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); }