Encryption and Decryption of String according to given technique

Given a string S, the task is to encrypt the string and decrypt the string again to the original form.
Encryption Technique: If L is the length of the string, then take two values, one the ceil of √L (say b), and the other floor of √L (say a), and make a two-dimensional matrix having rows = a, and columns = b.
If rows*columns < L, then increase the value of a or b, whichever is minimum. Fill the matrix with the characters of the original string sequentially. After obtaining the matrix, read the matrix column-wise and print the obtained string.

Decryption Technique: If L is the length of the encrypted string, then again find the two values a and b, where a is the ceil value of the √L and b is the floor value of the √L. Similarly create a 2D Matrix in which store the string column wise and read the matrix row-wise to get the string in the original form.

Encryption Approach:

  • Find the length L of the string.
  • Find the ceil and floor values of √Length and assign them to the variables.
  • Check if the product of the two variables >= Length, if not then increment the variable having lesser value by 1.
  • Create a 2D matrix and fill the characters of the string row-wise.
  • Read the matrix column-wise to get the encrypted string.

Decryption Approach:

  • Find the length L of the string.
  • Find the ceil and floor values of √Length and assign them to the variables.
  • Create a 2D matrix and fill the matrix by characters of string column-wise.
  • Read the matrix row-wise to get the decrypted string.

Below is the implementation of the above approach:

C++

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// C++ implementation for Custom
// Encryption and Decryption of String
  
#include <bits/stdc++.h>
using namespace std;
  
// Function to encrypt the string
string encryption(string s)
{
    int l = s.length();
    int b = ceil(sqrt(l));
    int a = floor(sqrt(l));
    string encrypted;
    if (b * a < l) {
        if (min(b, a) == b) {
            b = b + 1;
        }
        else {
            a = a + 1;
        }
    }
  
    // Matrix to generate the 
    // Encrypted String
    char arr[a][b];
    memset(arr, ' ', sizeof(arr));
    int k = 0;
      
    // Fill the matrix row-wise
    for (int j = 0; j < a; j++) {
        for (int i = 0; i < b; i++) {
            if (k < l){
                arr[j][i] = s[k];
            }
            k++;
        }
    }
  
    // Loop to generate 
    // encrypted string
    for (int j = 0; j < b; j++) {
        for (int i = 0; i < a; i++) {
            encrypted = encrypted + 
                         arr[i][j];
        }
    }
    return encrypted;
}
  
// Function to decrypt the string
string decryption(string s){
    int l = s.length();
    int b = ceil(sqrt(l));
    int a = floor(sqrt(l));
    string decrypted;
  
    // Matrix to generate the 
    // Encrypted String
    char arr[a][b];
    memset(arr, ' ', sizeof(arr));
    int k = 0;
      
    // Fill the matrix column-wise
    for (int j = 0; j < b; j++) {
        for (int i = 0; i < a; i++) {
            if (k < l){
                arr[j][i] = s[k];
            }
            k++;
        }
    }
  
    // Loop to generate 
    // decrypted string
    for (int j = 0; j < a; j++) {
        for (int i = 0; i < b; i++) {
            decrypted = decrypted + 
                         arr[i][j];
        }
    }
    return decrypted;
}
  
// Driver Code
int main()
{
    string s = "Geeks For Geeks";
    string encrypted;
    string decrypted;
      
    // Encryption of String
    encrypted = encryption(s);
    cout << encrypted << endl;
      
    // Decryption of String
    decrypted = decryption(encrypted);
    cout << decrypted;
    return 0;
}

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Java














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// Java implementation for Custom 


// Encryption and Decryption of String 


class GFG 


{ 


  


// Function to encrypt the String 


static String encryption(char[] s) 


{ 


    int l = s.length; 


    int b = (int) Math.ceil(Math.sqrt(l)); 


    int a = (int) Math.floor(Math.sqrt(l)); 


    String encrypted = ""; 


    if (b * a < l) 


    { 


        if (Math.min(b, a) == b)  


        { 


            b = b + 1; 


        } 


        else


        { 


            a = a + 1; 


        } 


    } 


  


    // Matrix to generate the  


    // Encrypted String 


    char [][]arr = new char[a][b]; 


    int k = 0; 


      


    // Fill the matrix row-wise 


    for (int j = 0; j < a; j++)  


    { 


        for (int i = 0; i < b; i++)  


        { 


            if (k < l) 


            { 


                arr[j][i] = s[k]; 


            } 


            k++; 


        } 


    } 


  


    // Loop to generate  


    // encrypted String 


    for (int j = 0; j < b; j++)  


    { 


        for (int i = 0; i < a; i++)  


        { 


            encrypted = encrypted +  


                        arr[i][j]; 


        } 


    } 


    return encrypted; 


} 


  


// Function to decrypt the String 


static String decryption(char []s) 


{ 


    int l = s.length; 


    int b = (int) Math.ceil(Math.sqrt(l)); 


    int a = (int) Math.floor(Math.sqrt(l)); 


    String decrypted=""; 


  


    // Matrix to generate the  


    // Encrypted String 


    char [][]arr = new char[a][b]; 


    int k = 0; 


      


    // Fill the matrix column-wise 


    for (int j = 0; j < b; j++)  


    { 


        for (int i = 0; i < a; i++)  


        { 


            if (k < l) 


            { 


                arr[j][i] = s[k]; 


            } 


            k++; 


        } 


    } 


  


    // Loop to generate  


    // decrypted String 


    for (int j = 0; j < a; j++)  


    { 


        for (int i = 0; i < b; i++)  


        { 


            decrypted = decrypted +  


                        arr[i][j]; 


        } 


    } 


    return decrypted; 


} 


  


// Driver Code 


public static void main(String[] args) 


{ 


    String s = "Geeks For Geeks"; 


    String encrypted; 


    String decrypted; 


      


    // Encryption of String 


    encrypted = encryption(s.toCharArray()); 


    System.out.print(encrypted +"\n"); 


      


    // Decryption of String 


    decrypted = decryption(encrypted.toCharArray()); 


    System.out.print(decrypted); 


} 


} 


  


// This code is contributed by PrinciRaj1992 



















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Python3














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# Python3 implementation for Custom 


# Encryption and Decryption of String 


from math import ceil,floor,sqrt 


  


# Function to encrypt the 


def encryption(s): 


    l = len(s) 


    b = ceil(sqrt(l)) 


    a = floor(sqrt(l)) 


    encrypted="" 


    if (b * a < l): 


        if (min(b, a) == b): 


            b = b + 1


        else: 


            a = a + 1


  


    # Matrix to generate the 


    # Encrypted String 


    arr = [[' ' for i in range(a)] for j in range(b)] 


    k = 0


  


    # Fill the matrix row-wise 


    for j in range(a): 


        for i in range(b): 


            if (k < l): 


                arr[j][i] = s[k] 


            k += 1


  


    # Loop to generate 


    # encrypted 


    for j in range(b): 


        for i in range(a): 


            encrypted = encrypted + arr[i][j] 


  


    return encrypted 


  


# Function to decrypt the 


def decryption(s): 


    l = len(s) 


    b = ceil(sqrt(l)) 


    a = floor(sqrt(l)) 


    decrypted="" 


  


    # Matrix to generate the 


    # Encrypted String 


    arr = [[' ' for i in range(a)] for j in range(b)] 


    k = 0


  


    # Fill the matrix column-wise 


    for j in range(b): 


        for i in range(a): 


            if (k < l): 


                arr[j][i] = s[k] 


            k += 1


  


    # Loop to generate 


    # decrypted 


    for j in range(a): 


        for i in range(b): 


            decrypted = decrypted + arr[i][j] 


    return decrypted 


  


# Driver Code 


  


s = "Geeks For Geeks"


encrypted="" 


decrypted="" 


  


# Encryption of String 


encrypted = encryption(s) 


print(encrypted) 


  


# Decryption of String 


decrypted = decryption(encrypted) 


print(decrypted) 


  


# This code is contributed by mohit kumar 29 



















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C#














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// C# implementation for Custom 


// Encryption and Decryption of String 


using System; 


  


class GFG 


{ 


   


// Function to encrypt the String 


static String encryption(char[] s) 


{ 


    int l = s.Length; 


    int b = (int) Math.Ceiling(Math.Sqrt(l)); 


    int a = (int) Math.Floor(Math.Sqrt(l)); 


    String encrypted = ""; 


    if (b * a < l) 


    { 


        if (Math.Min(b, a) == b)  


        { 


            b = b + 1; 


        } 


        else


        { 


            a = a + 1; 


        } 


    } 


   


    // Matrix to generate the  


    // Encrypted String 


    char [,]arr = new char[a, b]; 


    int k = 0; 


       


    // Fill the matrix row-wise 


    for (int j = 0; j < a; j++)  


    { 


        for (int i = 0; i < b; i++)  


        { 


            if (k < l) 


            { 


                arr[j, i] = s[k]; 


            } 


            k++; 


        } 


    } 


   


    // Loop to generate  


    // encrypted String 


    for (int j = 0; j < b; j++)  


    { 


        for (int i = 0; i < a; i++)  


        { 


            encrypted = encrypted +  


                        arr[i, j]; 


        } 


    } 


    return encrypted; 


} 


   


// Function to decrypt the String 


static String decryption(char []s) 


{ 


    int l = s.Length; 


    int b = (int) Math.Ceiling(Math.Sqrt(l)); 


    int a = (int) Math.Floor(Math.Sqrt(l)); 


    String decrypted=""; 


   


    // Matrix to generate the  


    // Encrypted String 


    char [,]arr = new char[a, b]; 


    int k = 0; 


       


    // Fill the matrix column-wise 


    for (int j = 0; j < b; j++)  


    { 


        for (int i = 0; i < a; i++)  


        { 


            if (k < l) 


            { 


                arr[j, i] = s[k]; 


            } 


            k++; 


        } 


    } 


   


    // Loop to generate  


    // decrypted String 


    for (int j = 0; j < a; j++)  


    { 


        for (int i = 0; i < b; i++)  


        { 


            decrypted = decrypted +  


                        arr[i, j]; 


        } 


    } 


    return decrypted; 


} 


   


// Driver Code 


public static void Main(String[] args) 


{ 


    String s = "Geeks For Geeks"; 


    String encrypted; 


    String decrypted; 


       


    // Encryption of String 


    encrypted = encryption(s.ToCharArray()); 


    Console.Write(encrypted +"\n"); 


       


    // Decryption of String 


    decrypted = decryption(encrypted.ToCharArray()); 


    Console.Write(decrypted); 


} 


} 


  


// This code is contributed by PrinciRaj1992 



















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Output:


Gsree  keFGskoe 
Geeks For Geeks







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