Null Cipher
A null cipher, also known as concealment cipher, is an ancient form of encryption where the plaintext is mixed with a large amount of non-cipher material. Today it is regarded as a simple form of steganography, which can be used to hide ciphertext.
There are various options of using the Null Cipher. Here we are taking the first letter from each word successively. The pattern can be chosen to increase the cryptography level Other options can be:
- Taking last letters from each word.
- Taking the letter from the particular position
- Using the pattern (1, 2, 3, 1, 2, 3 [each letter in each word]). You can use some other pattern also.
- Positing of the significant letters next to or at certain intervals from punctuation marks or particular characters.
Null Cipher taking the first letter from each word successively
More Examples of messages containing null ciphers:
Input will be one paragraph or sentence without any newline. Input : News Eight Weather: Tonight increasing snow. Unexpected precipitation smothers eastern towns. Be extremely cautious and use snowtires especially heading east. The [highway is not] knowingly slippery. Highway evacuation is suspected. Police report emergency situations in downtown ending near Tuesday. Explanation: Taking the first letter in each word successively yields the real message. Here we are converting decoded message to lowercase. News Eight Weather: Tonight Increasing Snow. Unexpected Precipitation Smothers Eastern Towns. Be Extremely Cautious And Use Snowtires Especially Heading East. The [Highway Is Not] Knowingly Slippery. Highway Evacuation Is Suspected. Police Report Emergency Situations In Downtown Ending Near Tuesday. Output : After Deciphered : newtisupsetbecausehethinksheispresident After breaking the words manually the output will be: Newt is upset because he thinks he is President
Implementation:
C++
// CPP program to decode NULL CIPHER #include <bits/stdc++.h> using namespace std; string decode(string str) { // Store the decoded string. string res = "" ; // found variable is used to tell that the encoded // encoded character is found in that particular word. bool found = false ; for ( int i = 0; i < str.size(); i++) { // Set found variable to false whenever we find // whitespace, meaning that encoded character for // new word is not found if (str[i] == ' ' ) { found = false ; continue ; } if (!found) { if (str[i] >= 'A' && str[i] <= 'Z' ) { res += str[i] + 32; found = true ; } else if (str[i] >= 'a' && str[i] <= 'z' ) { res += str[i]; found = true ; } } } return res; } // Driver code int main() { string in; in = "A Step by Step Guide for Placement Preparation by GeeksforGeeks" ; cout << "Enciphered Message: " ; // Function call cout << decode(in) << endl; return 0; } |
Java
// Java program to decode NULL CIPHER class GFG { // Function to decode the message. static String decode(String str) { // Store the decoded string String res = "" ; // found variable is used // to tell that the encoded // encoded character is // found in that particular word. boolean found = false ; for ( int i = 0 ; i < str.length(); i++) { // Set found variable to false // whenever we find // whitespace, meaning that // encoded character for // new word is not found if (str.charAt(i) == ' ' ) { found = false ; continue ; } if (!found) { if ((str.charAt(i) >= 'A' && str.charAt(i) <= 'Z' ) || (str.charAt(i) >= 'a' && str.charAt(i) <= 'z' )) { res += Character.toString(str.charAt(i)); found = true ; } } } return res.toLowerCase(); } // Driver Code public static void main(String[] args) { String in; in = "A Step by Step Guide for Placement Preparation by GeeksforGeeks" ; System.out.println( "Enciphered Message: " + decode(in)); } } // This code is contributed by Vivek Kumar Singh |
Python3
# Python program to decode NULL CIPHER # Function to decode the message. def decode(string): # Store the decoded string res = "" # found variable is used # to tell that the encoded # encoded character is # found in that particular word. found = False for character in string: # Set found variable to false # whenever we find # whitespace, meaning that # encoded character for # new word is not found if character = = ' ' : found = False continue if not found: if character> = 'A' and character< = 'Z' or character> = 'a' and character< = 'z' : res + = character found = True return res.lower() # Driver code if __name__ = = "__main__" : input = "A Step by Step Guide for Placement Preparation by GeeksforGeeks" print ( "Enciphered Message:" ,decode( input )) # This code is contributed by Vivek Kumar Singh |
C#
// A C# program to decode NULL CIPHER using System; class GFG { // Function to decode the message. static String decode(String str) { // Store the decoded string String res = "" ; // found variable is used // to tell that the encoded // encoded character is // found in that particular word. Boolean found = false ; for ( int i = 0; i < str.Length; i++) { // Set found variable to false whenever we find // whitespace, meaning that encoded character for // new word is not found if (str[i] == ' ' ) { found = false ; continue ; } if (!found) { if (str[i] >= 'A' && str[i] <= 'Z' ) { res += ( char )(str[i] + 32); found = true ; } else if (str[i] >= 'a' && str[i] <= 'z' ) { res += ( char )str[i]; found = true ; } } } return res; } // Driver Code public static void Main(String[] args) { String str; str = "A Step by Step Guide for Placement Preparation by GeeksforGeeks" ; Console.WriteLine( "Enciphered Message: " + decode(str)); } } // This code has been contributed by 29AjayKumar |
Javascript
<script> // Javascript program to decode NULL CIPHER // Function to decode the message. function decode(str) { // Store the decoded string let res = "" ; // found variable is used // to tell that the encoded // encoded character is // found in that particular word. let found = false ; for (let i = 0; i < str.length; i++) { // Set found variable to false // whenever we find // whitespace, meaning that // encoded character for // new word is not found if (str[i] == ' ' ) { found = false ; continue ; } if (!found) { if ((str[i] >= 'A' && str[i] <= 'Z' ) || (str[i] >= 'a' && str[i] <= 'z' )) { res += (str[i]); found = true ; } } } return res.toLowerCase(); } // Driver Code let In = "A Step by Step Guide for Placement Preparation by GeeksforGeeks" ; document.write( "Enciphered Message: " + decode(In)); // This code is contributed by rag2127 </script> |
Enciphered Message: asbsgfppbg
Complexity Analysis: The time complexity of the decode() function is O(n), where n is the length of the input string. This is because the function iterates over each character in the string only once. The space complexity of the function is also O(n), because the size of the output string is proportional to the size of the input string.
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