Vpropel VIT | POD | 21/05/2020 | Cipher text generation | 25

cipher_text_generation.cpp

#include <iostream>
#include<string>
#include<ctype.h>
using namespace std;
void getKeyMatrix(string key, int keyMatrix[][3])
{
    int k = 0;
    for (int i = 0; i < 3; i++)
    {
        for (int j = 0; j < 3; j++)
        {
            keyMatrix[i][j] = (key[k]) % 65;
            k++;
        }
    }
}
void encrypt(int cipherMatrix[][1],int keyMatrix[][3],int messageVector[][1])
{
    int x, i, j;
    for (i = 0; i < 3; i++)
    {
        for (j = 0; j < 1; j++)
        {
            cipherMatrix[i][j] = 0;

             for (x = 0; x < 3; x++)
            {
                cipherMatrix[i][j] +=
                     keyMatrix[i][x] * messageVector[x][j];
            }

            cipherMatrix[i][j] = cipherMatrix[i][j] % 26;
        }
    }
}

void cypher(string message, string key)
{

    int keyMatrix[3][3];
    getKeyMatrix(key, keyMatrix);
    int messageVector[3][1];
    for (int i = 0; i < 3; i++)
        messageVector[i][0] = (message[i]) % 65;
    int cipherMatrix[3][1];
    encrypt(cipherMatrix, keyMatrix, messageVector);
    string CipherText;
    for (int i = 0; i < 3; i++)
        CipherText += cipherMatrix[i][0] + 65;
    cout <<CipherText;
}
int main()
{
    string msg;
    cin>>msg;
    string key;
    cin>>key;
    if(key.length()!=9)
        {cout<<"enter 9 letter key"; exit(1);}
    for(int i=0;i<msg.length();i++)
        if(islower(msg[i]))
            msg[i]-=32;
    for(int i=0;i<key.length();i++)
        if(islower(key[i]))
            key[i]-=32;
    cypher(msg, key);
    return 0;
}

cipher_text_generation.py

def encrypt(msg_matrix,key_matrix):
    emsg=[]
    for i in range(3):
        temp=0
        for j in range(3):
            temp+=msg_matrix[j]*key_matrix[i][j]
        emsg.append(chr(temp%26+65))
    print(''.join(emsg))
def cypher(msg,key):
    msg_matrix=[ord(msg[i])%65 for i in range(3)]
    temp=0;
    key_matrix=[]
    k=0
    for i in range(3):
        temp=[]
        for j in range(3):
            temp.append(ord(key[k])%65)
            k+=1
        key_matrix.append(temp)
    encrypt(msg_matrix,key_matrix)
message=input().upper()
key=input().upper()
if len(key)!=9:
  print("enter 9 letter key")
  exit(None)
cypher(message,key)

Question(cipher_text_generation).txt

Cipher text generation
Encryption is a security technique where the text message is converted into unreadable form called as Cipher text.

Generate a cipher text using polygraphic substitution method based on linear algebra. Each letter is represented by a number modulo 26.

To encrypt a message, each block of n letters (considered as an n-component vector) is multiplied by an invertible n × n matrix, against modulus 26.

The matrix used for encryption is the cipher key, and it should be chosen randomly from the set of invertible n × n matrices (modulo 26).

Generate a cipher text for a text message of 3 letter alphabet. Hence the key should be 3*3 matrix.

Check whether given key satisfies 9 characters in it. If not, popup the message for entering 9 letter key.

Example:

Encryption:

We have to encrypt the message ‘ACT’.The key is ‘GYBNQKURP’ which 9 in characters hence can be written as the 3x3 matrix:

The message ‘ACT’ is written as vector:


Multiplied by key matrix, encrypted output is

https://www.geeksforgeeks.org/hill-cipher/
(for images n question)

Corresponding output is “POH”

Input Format

Text message: ACT

Key: GYBNQKURP

Output Format

Cipher text: POH

https://www.geeksforgeeks.org/hill-cipher/

Awesome. Thanks a lot Dude :)