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Encrypt the License File - and Before Retrieve Decrypt the same

Hi,

Kindly share the code for encrypting the license file forever and before setting license it has to get decrypted and read the content.

Thanks & Regards,
Poornima K

Hi Poornima,

Thanks for your posting and using Aspose.Cells.

You can encrypt your License string with simple XOR operation using some integer KEY and it will give you encrypted license string. You can then save this string in some file. Later on, you can read this encrypted license string and then XOR it with the same integer KEY and it will decrypt your encrypted license string and then you can use this decrypted license string to set your license.

For example, please see the following code. It has a method that encrypts and decrypts any string. The second method test this method with a sample string and prints in debug window. Please check the debug output of this code at below.

C#


static string EncryptDecryptLicense(int key, string input)

{

//Read original file as byte array

char[] originalBytes = input.ToCharArray();


//Create output string

string outputString = string.Empty;


//Loop through all bytes in original array and encode each byte using XOR operation

for (int i = 0; i < originalBytes.Length; i++)

{

outputString += (char)(originalBytes[i] ^ key);

}


return outputString;


}


void RUN()

{

int YOUR_XOR_KEY = 194;

string YOUR_LICENSE_STRING = “This is a simple license text. Use your own license string here.”;


string encryptedLicense = EncryptDecryptLicense(YOUR_XOR_KEY, YOUR_LICENSE_STRING);


//Print your encoded license

Debug.WriteLine("Encrypted License: " + encryptedLicense);


//Now decode your encoded license

string decryptedLicense = EncryptDecryptLicense(YOUR_XOR_KEY, encryptedLicense);


//Print your decoded license

Debug.WriteLine("Decrypted License: " + decryptedLicense);


}

Debug Console Output:
Encrypted License: –ª«±â«±â£â±«¯²®§â®«¡§¬±§â¶§º¶ì◱§â»­·°â­µ¬â®«¡§¬±§â±¶°«¬¥âª§°§ì
Decrypted License: This is a simple license text. Use your own license string here.

Once, you get your decrypted license string, you can set the license in this way. First, you will convert your decrypted license string into memory stream and then pass it to License.SetLicense() method.

C#
//Your decrypted license string
string decryptedLicense = ...

MemoryStream licStrm = new System.IO.MemoryStream(Encoding.UTF8.GetBytes(decryptedLicense));

//Set license
Aspose.Cells.License lic = new Aspose.Cells.License();
lic.SetLicense(licStrm);

Hi,


I am wondering why would we need to encrypt and decrypt the license file before setting the it to license method?

Also in above code where are you saving the encrypted content to disk? disk here means any file or any other means of storage

Thanks

Hi,

Thanks for your posting and using Aspose.Cells.

If you will encrypt the license, then you can save its content in any file on disk. This way, no one can steal your license because it is encrypted and no use for anyone. Only, you know how to decrypt it back and set the license.

This approach works for any file which you do not want to reveal or get stolen by anyone. For example, in ASP.NET web application, people encrypts web.config file with some encryption algorithm to save it from being stolen by others because it might contain some confidential data.

Thanks for your reply,

But here web.config or .lic must be on a folder in any OS before it has to be encrypted. so in that case there is a possibility of steal by someone right?

here you are trying to encrypt and decrpt the license file which will be on disk. So anyone can steal it? what is the use of encrypt the file that is already on disk and again decrypt it?

where do you think the orginal .lic file to be placed before encrypt?

Thanks

Hi,

Thanks for your posting and using Aspose.Cells.

No, you will not place the original file on disk. You will only place encrypted file on disk.

For example, if your file contains “This is my hello string” and you encrypt it once say “xsaskllkamklmasdm”, then you will delete your original file containing “This is my hello string” and only place the encrypted file containing “xsaskllkamklmasdm” on disk.

Now, if someone steals your encrypted file containing “xsaskllkamklmasdm”, then it is of no use to him because he does not understand the encrypted contents.

Only, you know the encrypted contents and you can decrypt “xsaskllkamklmasdm” back to “This is my hello string”.

Many applications stores their confidential information on disk in encrypted form which no one can understand except they themselves.

FYI:
.NET framework APIs provide many advanced encryption algorithm which you can use to encrypt your contents with very strong encryption.

HI Brother,

is there any option for Decrypt .lic File

@sanu1008,

Please refer to Protecting your License File for information on how to protect your .NET, Java or Android license. To access the page, you need to be logged in and have at least one paid order.

If you have questions about our licenses, read the Licensing FAQ.