Encryption and Decryption of String according to given technique (original) (raw)

Last Updated : 27 Dec, 2022

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 increments the variable having a 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++ `

// 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;

}

Java

// 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

Python3

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

C#

// 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

JavaScript

`

Output:

Gsree keFGskoe Geeks For Geeks

Time Complexity: O(?n * ?n) ? O(n)
Auxiliary Space: O(n), where n is the length of the given string.