decryption filter

[ls1984]

Hello, How can decrypt the file that the program below encrypt?
Please I need with this.



// This program encrypts a file

#include<iostream>
#include<fstream>

using namespace std;

int main()
{
const int ENCRYPT=10; // amount to add to a chor
const int SIZE= 255; // array size
char inFileName[SIZE];
char data; // to hold a char from a file

ifstream inputFile; // input file stream object
ofstream outputFile; // output file stream object


// Get the name of the input file.
cout<< "Enter the name of the file to encrypt.\n";
cin.getline(inFileName, SIZE);

// Open the files.
inputFile.open (inFileName);
outputFile.open("encrypted.txt");

// Readnthe first character from the input file.
inputFile.get(data);

//While data is available from the input file
// encrypt it and write to the output file.

while( !inputFile.eof())
{
// Encrypt the character.

data += ENCRYPT;

// Write the encrypted data.
outputFile.put(data);

//Read the next character.
inputFile.get(data);
}
// Close the files.

inputFile.close();
outputFile.close();

// We're done

cout<< "The file " << inFileName
<< " was encrypted and saved to encrypted.txt."
<< endl;
system("pause");
return 0;

[randisking]

To decrypt something that is encrypted, you are essentially reversing the process. You need the encryption key, which you have already (ENCRYPT), so you just need a function that takes your encrypted file and reverses the encryption.

[joneele]

agree with randisking, however in some cases there are no way to reverse the encryption but in your code it so easy

input: 123

1  2  3   text
;  <  =   after encrypting

how this happens?

1  2  3   text
49 50 51  decimal
59 60 61 << ENCRYPT adds 10 to each...
;  <  =   text 

so as randisking said

;  <  =   text
59 60 61
49 50 51  << after subtracting 10
1  2  3   text