Custom Building Cryptography Algorithms (Hybrid Cryptography)

Cryptography can be defined as an art of encoding and decoding the patterns (in the form of messages).

Cryptography is a very straightforward concept which deals with manipulating the strings (or text) to make them unreadable for the intermediate person. It has a very effective way to encrypt or decrypts the text coming from the other parties. Some of the examples are, Caesar Cipher, Viginere Cipher, Columnar Cipher, DES, AES and the list continues. To develop custom cryptography algorithm, hybrid encryption algorithms can be used. 

Hybrid Encryption is a concept in cryptography which combines/merge one/two cryptography algorithms to generate more effective encrypted text.

Example:

FibBil Cryptography Algorithm

Problem Statement:

Program to generate an encrypted text, by computing Fibonacci Series, adding the terms of Fibonacci Series with each plaintext letter, until the length of the key.

Algorithm:

For Encryption: Take an input plain text and key from the user, reverse the plain text and concatenate the plain text with the key, Copy the string into an array. After copying, separate the array elements into two parts, EvenArray, and OddArray in which even index of an array will be placed in EvenArray and same for OddArray. Start generating the Fibonacci Series F(i) up-to-the length of the key_j such that c=i+j where c is cipher text with mod 26. Append all the c^th elements in a CipherString and, so Encryption Done!. When sum up concept is use, it highlights of implementing Caesar Cipher. 

For Decryption: Vice Versa of the Encryption Algorithm

Example for the Algorithm: 
 

Input: hello 
Key: abcd 
Output: riobkxezg 
Reverse the input, olleh, append this with the key i.e. ollehabcd. 
EvenString: leac 
OddString: olhbd
As key length is 4, 4 times loop will be generated including FibNum 0, which is ignored.
For EvenArray Ciphers: 
FibNum: 1 
In Even Array for l and FibNum 1 cip is k 
In Even Array for e and FibNum 1 cip is d 
In Even Array for a and FibNum 1 cip is z 
In Even Array for c and FibNum 1 cip is b 
FibNum: 2 
In Even Array for l and FibNum 2 cip is j 
In Even Array for e and FibNum 2 cip is c 
In Even Array for a and FibNum 2 cip is y 
In Even Array for c and FibNum 2 cip is a 
FibNum: 3 (Final Computed letters) 
In Even Array for l and FibNum 3 cip is i 
In Even Array for e and FibNum 3 cip is b 
In Even Array for a and FibNum 3 cip is x 
In Even Array for c and FibNum 3 cip is z
For OddArray Ciphers 
FibNum: 1 
In Odd Array for o and FibNum 1 cip is p 
In Odd Array for l and FibNum 1 cip is m 
In Odd Array for h and FibNum 1 cip is i 
In Odd Array for b and FibNum 1 cip is c 
In Odd Array for d and FibNum 1 cip is e 
FibNum: 2 
In Odd Array for o and FibNum 2 cip is q 
In Odd Array for l and FibNum 2 cip is n 
In Odd Array for h and FibNum 2 cip is j 
In Odd Array for b and FibNum 2 cip is d 
In Odd Array for d and FibNum 2 cip is f 
FibNum: 3 (Final Computed letters) 
In Odd Array for o and FibNum 3 cip is r 
In Odd Array for l and FibNum 3 cip is o 
In Odd Array for h and FibNum 3 cip is k 
In Odd Array for b and FibNum 3 cip is e 
In Odd Array for d and FibNum 3 cip is g

Arrange EvenArrayCiphers and OddArrayCiphers in their index order, so final String Cipher will be, riobkxezg

Program:

#include<bits/stdc++.h>  using namespace std;  string encryptText(string password, string key)  {   int a = 0, b = 1, c = 0,  m = 0, k = 0, j = 0;   string cipher = "", temp = "";   // Declare a password string   string pw = password;   // Reverse the String   reverse(pw.begin(), pw.end());   pw = pw + key;   // For future Purpose   temp = pw;  string stringArray = temp;  string evenString = "", oddString = "";   // Declare EvenArray for storing   // even index of stringArray   string evenArray;   // Declare OddArray for storing   // odd index of stringArray   string oddArray;   // Storing the positions in their   // respective arrays   for(int i = 0;   i < stringArray.length(); i++)  {   if (i % 2 == 0)   {   oddString = oddString +   stringArray[i];   }   else   {   evenString = evenString +   stringArray[i];   }   }   evenArray = new char[evenString.length()];   oddArray = new char[oddString.length()];   // Generate a Fibonacci Series   // Upto the Key Length   while (m <= key.length())  {    // As it always starts with 1   if (m == 0)   m = 1;   else  {     // Logic For Fibonacci Series   a = b;   b = c;   c = a + b;    for(int i = 0;   i < evenString.length();  i++)  {     // Caesar Cipher Algorithm Start  // for even positions   int p = evenString[i];   int cip = 0;     if (p == '0' || p == '1' ||  p == '2' || p == '3' ||   p == '4' || p == '5' ||  p == '6' || p == '7' ||  p == '8' || p == '9')  {   cip = p - c;     if (cip < '0')   cip = cip + 9;   }   else  {   cip = p - c;   if (cip < 'a')  {   cip = cip + 26;   }   }   evenArray[i] = (char)cip;     // Caesar Cipher Algorithm End  }   for(int i = 0;   i < oddString.length();  i++)  {     // Caesar Cipher Algorithm   // Start for odd positions   int p = oddString[i];   int cip = 0;     if (p == '0' || p == '1' ||   p == '2' || p == '3' ||   p == '4' || p == '5' ||  p == '6' || p == '7' ||   p == '8' || p == '9')  {   cip = p + c;   if (cip > '9')   cip = cip - 9;   }   else  {   cip = p + c;   if (cip > 'z')  {   cip = cip - 26;   }   }   oddArray[i] = (char)cip;     // Caesar Cipher Algorithm End   }   m++;   }   }   // Storing content of even and   // odd array to the string array   for(int i = 0; i < stringArray.size(); i++)  {   if (i % 2 == 0)  {   stringArray[i] = oddArray[k];   k++;   }   else  {   stringArray[i] = evenArray[j];   j++;   }   }     // Generating a Cipher Text   // by stringArray (Caesar Cipher)   for(char d : stringArray)  {   cipher = cipher + d;   }     // Return the Cipher Text   return cipher;  }  // Driver code int main()  {   string pass = "hello";   string key = "abcd";     cout << encryptText(pass, key);   return 0; }  // This code is contributed by himanshu77 

import java.util.*; import java.lang.*; class GFG {  public static void main(String[] args)  {  String pass = "hello";  String key = "abcd";  System.out.println(encryptText(pass, key));  }  public static String encryptText(String password, String key)  {  int a = 0, b = 1, c = 0, m = 0, k = 0, j = 0;  String cipher = "", temp = "";  // Declare a password string  StringBuffer pw = new StringBuffer(password);  // Reverse the String  pw = pw.reverse();  pw = pw.append(key);  // For future Purpose  temp = pw.toString();  char stringArray[] = temp.toCharArray();  String evenString = "", oddString = "";  // Declare EvenArray for storing  // even index of stringArray  char evenArray[];  // Declare OddArray for storing  // odd index of stringArray  char oddArray[];  // Storing the positions in their respective arrays  for (int i = 0; i < stringArray.length; i++) {  if (i % 2 == 0) {  oddString = oddString + Character.toString(stringArray[i]);  }  else {  evenString = evenString + Character.toString(stringArray[i]);  }  }  evenArray = new char[evenString.length()];  oddArray = new char[oddString.length()];  // Generate a Fibonacci Series  // Upto the Key Length  while (m <= key.length()) {  // As it always starts with 1  if (m == 0)  m = 1;  else {  // Logic For Fibonacci Series  a = b;  b = c;  c = a + b;  for (int i = 0; i < evenString.length(); i++) {  // Caesar Cipher Algorithm Start for even positions  int p = evenString.charAt(i);  int cip = 0;  if (p == '0' || p == '1' || p == '2' || p == '3' || p == '4'  || p == '5' || p == '6'  || p == '7' || p == '8' || p == '9') {  cip = p - c;  if (cip < '0')  cip = cip + 9;  }  else {  cip = p - c;  if (cip < 'a') {  cip = cip + 26;  }  }  evenArray[i] = (char)cip;  /* Caesar Cipher Algorithm End*/  }  for (int i = 0; i < oddString.length(); i++) {  // Caesar Cipher Algorithm Start for odd positions  int p = oddString.charAt(i);  int cip = 0;  if (p == '0' || p == '1' || p == '2' || p == '3' || p == '4'  || p == '5' || p == '6'  || p == '7' || p == '8' || p == '9') {  cip = p + c;  if (cip > '9')  cip = cip - 9;  }  else {  cip = p + c;  if (cip > 'z') {  cip = cip - 26;  }  }  oddArray[i] = (char)cip;  // Caesar Cipher Algorithm End  }  m++;  }  }  // Storing content of even and  // odd array to the string array  for (int i = 0; i < stringArray.length; i++) {  if (i % 2 == 0) {  stringArray[i] = oddArray[k];  k++;  }  else {  stringArray[i] = evenArray[j];  j++;  }  }  // Generating a Cipher Text  // by stringArray (Caesar Cipher)  for (char d : stringArray) {  cipher = cipher + d;  }  // Return the Cipher Text  return cipher;  } } 

// C# code to implement the approach using System; using System.Collections.Generic; class GFG {  // Driver Code  public static void Main(string[] args)  {  string pass = "hello";  string key = "abcd";  Console.WriteLine(encryptText(pass, key));  }  public static string encryptText(string password,  string key)  {  int a = 0, b = 1, c = 0, m = 0, k = 0, j = 0;  string cipher = "", temp = "";  // Declare a password string  char[] pw = password.ToCharArray();  // Reverse the String  Array.Reverse(pw);  // For future Purpose  temp = new string(pw) + key;  char[] stringArray = temp.ToCharArray();  string evenString = "", oddString = "";  // Declare EvenArray for storing  // even index of stringArray  char[] evenArray;  // Declare OddArray for storing  // odd index of stringArray  char[] oddArray;  // Storing the positions in their respective arrays  for (int i = 0; i < stringArray.Length; i++) {  if (i % 2 == 0) {  oddString = oddString  + Char.ToString(stringArray[i]);  }  else {  evenString  = evenString  + Char.ToString(stringArray[i]);  }  }  evenArray = new char[evenString.Length];  oddArray = new char[oddString.Length];  // Generate a Fibonacci Series  // Upto the Key Length  while (m <= key.Length) {  // As it always starts with 1  if (m == 0)  m = 1;  else {  // Logic For Fibonacci Series  a = b;  b = c;  c = a + b;  for (int i = 0; i < evenString.Length;  i++) {  // Caesar Cipher Algorithm Start for  // even positions  int p = evenString[i];  int cip = 0;  if (p == '0' || p == '1' || p == '2'  || p == '3' || p == '4' || p == '5'  || p == '6' || p == '7' || p == '8'  || p == '9') {  cip = p - c;  if (cip < '0')  cip = cip + 9;  }  else {  cip = p - c;  if (cip < 'a') {  cip = cip + 26;  }  }  evenArray[i] = (char)cip;  /* Caesar Cipher Algorithm End*/  }  for (int i = 0; i < oddString.Length; i++) {  // Caesar Cipher Algorithm Start for odd  // positions  int p = oddString[i];  int cip = 0;  if (p == '0' || p == '1' || p == '2'  || p == '3' || p == '4' || p == '5'  || p == '6' || p == '7' || p == '8'  || p == '9') {  cip = p + c;  if (cip > '9')  cip = cip - 9;  }  else {  cip = p + c;  if (cip > 'z') {  cip = cip - 26;  }  }  oddArray[i] = (char)cip;  // Caesar Cipher Algorithm End  }  m++;  }  }  // Storing content of even and  // odd array to the string array  for (int i = 0; i < stringArray.Length; i++) {  if (i % 2 == 0) {  stringArray[i] = oddArray[k];  k++;  }  else {  stringArray[i] = evenArray[j];  j++;  }  }  // Generating a Cipher Text  // by stringArray (Caesar Cipher)  foreach(char d in stringArray)  {  cipher = cipher + d;  }  // Return the Cipher Text  return cipher;  } } // This code is contributed by phasing17 

# Python3 program to implement the approach def encryptText(password, key): a = 0 b = 1 c = 0 m = 0 k = 0 j = 0 cipher = "" temp = "" # Declare a password string pw = password # Reverse the String pw = pw[::-1] pw = pw + key # For future Purpose temp = pw stringArray = list(temp) evenString = "" oddString = "" # Declare EvenArray for storing # even index of stringArray evenArray = "" # Declare OddArray for storing # odd index of stringArray oddArray = "" # Storing the positions in their # respective arrays for i in range(len(stringArray)): if (i % 2 == 0): oddString = oddString + stringArray[i] else: evenString = evenString + stringArray[i] evenArray = ["" for _ in range(len(evenString))] oddArray = ["" for _ in range(len(oddString))] # Generate a Fibonacci Series # Upto the Key Length while (m <= len(key)): # As it always starts with 1 if (m == 0): m = 1 else: # Logic For Fibonacci Series a = b b = c c = a + b for i in range(len(evenString)): # Caesar Cipher Algorithm Start # for even positions p = evenString[i] cip = 0 if p in "1234567890": cip = ord(p) - c if (cip < ord('0')): cip = cip + 9 else: cip = ord(p) - c if (cip < ord('a')): cip = cip + 26 evenArray[i] = chr(cip) # Caesar Cipher Algorithm End for i in range(len(oddString)): # Caesar Cipher Algorithm # Start for odd positions p = oddString[i] cip = 0 if p in "0123456789": cip = ord(p) + c if (cip > ord('9')): cip = cip - 9 else: cip = ord(p) + c if (cip > ord('z')): cip = cip - 26 oddArray[i] = chr(cip) # Caesar Cipher Algorithm End m += 1 # Storing content of even and # odd array to the string array for i in range(len(stringArray)): if (i % 2 == 0): stringArray[i] = oddArray[k] k += 1 else: stringArray[i] = evenArray[j] j += 1 # Generating a Cipher Text # by stringArray (Caesar Cipher) for d in stringArray: cipher = cipher + d # Return the Cipher Text return cipher # Driver code pw = "hello" key = "abcd" print(encryptText(pw, key)) # This code is contributed by phasing17 

// Javascript code implementation  function encryptText(password, key) {  let a = 0, b = 1, c = 0, m = 0, k = 0, j = 0;  let cipher = "";  let temp = "";  // Declare a password string  let pass = password;  let pw = Array.from(pass);    // Reverse the String  pw.reverse();  for(let i = 0; i < Array.from(key).length; i++){  pw.push(Array.from(key)[i]);  }  // For future Purpose  temp = pw.join("");  let stringArray = temp.split('');  let evenString = "";  let oddString = "";    // Storing the positions in their respective arrays  for (let i = 0; i < stringArray.length; i++) {  if (i % 2 == 0) {  oddString = oddString + stringArray[i];  }  else {  evenString = evenString + stringArray[i];  }  }    // Declare EvenArray for storing  // even index of stringArray  let evenArray = new Array(evenString.length);  // Declare OddArray for storing  // odd index of stringArray  let oddArray = new Array(oddString.length);  // Generate a Fibonacci Series  // Upto the Key Length  while (m <= key.length) {  // As it always starts with 1  if (m == 0)  m = 1;  else {  // Logic For Fibonacci Series  a = b;  b = c;  c = a + b;  for (let i = 0; i < evenString.length; i++) {  // Caesar Cipher Algorithm Start for even positions  let p = evenString[i];  let cip = 0;  if (p == '0' || p == '1' || p == '2' || p == '3' || p == '4'  || p == '5' || p == '6'  || p == '7' || p == '8' || p == '9') {  cip = p.charCodeAt(0) - c;  if (cip < '0'.charCodeAt(0))  cip = cip + 9;  }  else {  cip = p.charCodeAt(0) - c;  if (cip < 'a'.charCodeAt(0)) {  cip = cip + 26;  }  }  evenArray[i] = String.fromCharCode(cip);  /* Caesar Cipher Algorithm End*/  }  for (let i = 0; i < oddString.length; i++) {  // Caesar Cipher Algorithm Start for odd positions  let p = oddString[i];  let cip = 0;  if (p == '0' || p == '1' || p == '2' || p == '3' || p == '4'  || p == '5' || p == '6'  || p == '7' || p == '8' || p == '9') {  cip = p + c;  if (cip > '9'.charCodeAt(0))  cip = cip - 9;  }  else {  cip = p.charCodeAt(0)+ c;  if (cip > 'z'.charCodeAt(0)) {  cip = cip - 26;  }  }  // console.log(cip);  oddArray[i] = String.fromCharCode(cip);  // Caesar Cipher Algorithm End  }  m++;  }  }  // Storing content of even and  // odd array to the string array  for (let i = 0; i < stringArray.length; i++) {  if (i % 2 == 0) {  stringArray[i] = oddArray[k];  k++;  }  else {  stringArray[i] = evenArray[j];  j++;  }  }  // Generating a Cipher Text  // by stringArray (Caesar Cipher)  for(let i = 0; i < stringArray.length; i++){  cipher = cipher + stringArray[i];  }  // Return the Cipher Text  return cipher; } let pass = "hello"; let key = "abcd"; console.log(encryptText(pass, key)); // The code is contributed by Nidhi goel.  

riobkxezg

Conclusion:

Hybrid Algorithms for the cryptography are effective and so, it is not very easy to detect the pattern and decode the message. Here, the algorithm is a combination of mathematical function and Caesar Cipher, so as to implement Hybrid Cryptography Algorithm.