cipher.cpp

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 * Copyright (C) Akiel Aries, <akiel@akiel.org>, et al.
 *
 * This software is licensed as described in the file LICENSE, which
 * you should have received as part of this distribution. The terms
 * among other details are referenced in the official documentation
 * seen here : https://akielaries.github.io/openGPMP/ along with
 * important files seen in this project.
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 * LICENSE file. As this is an Open Source effort, all implementations
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 * This software is distributed on an AS IS basis, WITHOUT
 * WARRANTY OF ANY KIND, either express or implied.
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/*
 * This file shows the implementation of some basic stream cipher
 * algorithms
 */
#include <cmath>
#include <cstdlib>
#include <iostream>
#include <openGPMP/nt/cipher.hpp>
#include <sstream>
#include <stdio.h>
#include <string>
 
std::string gpmp::Cipher::caesar(std::string plaintext, int64_t key) {
    std::string hashtext = "";
 
    for (int64_t i = 0; uint64_t(i) < plaintext.length(); i++) {
        // inject transformation
        if (isupper(plaintext[i])) {
            // upper case
            hashtext += char(int64_t(plaintext[i] + key - 65) % 26 + 65);
        } else {
            // lower case
            hashtext += char(int64_t(plaintext[i] + key - 97) % 26 + 97);
        }
    }
 
    return hashtext;
}
 
std::string gpmp::Cipher::keyword_encode(std::string key) {
    std::string encoded = "";
    // This array represents the 26 letters of alphabets
    bool arr[26] = {0};
 
    // This loop inserts the keyword at the start of the encoded
    // string
    for (int64_t i = 0; uint64_t(i) < key.size(); i++) {
        if (key[i] >= 'A' && key[i] <= 'Z') {
            /*
             * To check whether the character is inserted earlier
             * in the encoded string or not
             */
            if (arr[key[i] - 65] == 0) {
                encoded += key[i];
                arr[key[i] - 65] = 1;
            }
        } else if (key[i] >= 'a' && key[i] <= 'z') {
            if (arr[key[i] - 97] == 0) {
                encoded += key[i] - 32;
                arr[key[i] - 97] = 1;
            }
        }
    }
 
    // This loop inserts the remaining characters in the encoded
    // string.
    for (int64_t i = 0; i < 26; i++) {
        if (arr[i] == 0) {
            arr[i] = 1;
            encoded += char(i + 65);
        }
    }
    return encoded;
}
 
std::string gpmp::Cipher::keyword(std::string plaintext,
                                  std::string encoded_text) {
    std::string cipher = "";
 
    /*
     * This loop ciphered the message. Spaces, special characters
     * and numbers remain same.
     */
    for (int64_t i = 0; uint64_t(i) < plaintext.size(); i++) {
        if (plaintext[i] >= 'a' && plaintext[i] <= 'z') {
            int64_t pos = plaintext[i] - 97;
            cipher += encoded_text[pos];
        }
 
        else if (plaintext[i] >= 'A' && plaintext[i] <= 'Z') {
            int64_t pos = plaintext[i] - 65;
            cipher += encoded_text[pos];
        }
 
        else {
            cipher += plaintext[i];
        }
    }
    return cipher;
}