Encryption

Avuya Mxoli

Hi All,

I need help with a question here: I need to encrypt a 4 digit number in the ff way: add 7 and mod by 10 each digit then swap dgt1 with 3, 2 with 4. Then after that I need to decrypt the encrypted number. I need this in pseudocode but c# is welcome too. I know I have to store the user input in an array then manipulate it using a for loop then do the operations on each digit storing the results seperately. I then will have a function that will swap the digits as stated. I'm just not sure of how to apply this logically plz help in that regard oh and I have no clue on how to decrypt the number.
Thanks

3 Replies

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Vulpes15y ago
Accepted answer
Here it is in my (VB-like) pseudocode:

Function Encrypt(plain As String) As String

Create array of characters, digits, with 4 elements

For i = 0 To 3
n = Convert plain[i] to an integer
j = (n + 7) mod 10
c = Convert j to a character
digits[i] = c
Next

Swap 1st and 3rd elements of digits
Swap 2nd and 4th elements of digits

s = Convert digits to a string
Return s

End Function

Function Decrypt(encrypted As String) As String

digits = Convert encrypted to a character array
Swap 1st and 3rd elements of digits
Swap 2nd and 4th elements of digits

For i = 0 To 3
n = Convert digits[i] to an integer
j = n - 7
If (j < 0) j = j + 10
c = Convert j to a character
digits[i] = c
Next

s = Convert digits to a string
Return s

End Function

And here it is in C#:

using System;

class Program
{
static void Main()
{
string plain = "1234";
string encrypted = Encrypt(plain);
Console.WriteLine("Encrypted : {0}", encrypted);
plain = Decrypt(encrypted);
Console.WriteLine("Decrypted : {0}", plain);
Console.ReadKey();
}

static string Encrypt(string plain)
{
char[] digits = new char[4];

for(int i = 0; i < 4; i++)
{
int j = (plain[i] - 48 + 7) % 10;
digits[i] = (char)(j + 48);
}

char temp = digits[0];
digits[0] = digits[2];
digits[2] = temp;
temp = digits[1];
digits[1] = digits[3];
digits[3] = temp;
return new string(digits);
}

static string Decrypt(string encrypted)
{
char[] digits = encrypted.ToCharArray();
char temp = digits[0];
digits[0] = digits[2];
digits[2] = temp;
temp = digits[1];
digits[1] = digits[3];
digits[3] = temp;

for(int i = 0; i < 4; i++)
{
int j = digits[i] - 48 - 7;
if (j < 0) j += 10;
digits[i] = (char)(j + 48);
}

return new string(digits);
}

}
Mudia David11y ago
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace Palindrom { //this program encrpts an 4 didgt number AND changes its position class Program { static void Main() { string number; number = Console.ReadLine(); char a,b,c,d; a=number[0]; b=number[1]; c=number[2]; d=number[3]; int aEncript,bEncript,cEncript,dEncript; aEncript=(int.Parse(a.ToString()) *7) %10; bEncript=(int.Parse(b.ToString())*7) %10; cEncript=(int.Parse(c.ToString())*7) %10; dEncript=(int.Parse(d.ToString())*7) %10; string result = dEncript + "" + bEncript + "" + aEncript + "" + cEncript; Console.WriteLine(result); } } }
Avuya Mxoli15y ago
Thanks alot