Question

SO, in Visual C#.NET I would like it to somehow be able to taken in a program (through an open file dialog), then somehow take the bytes of that program and encrypt the bytes, to be executed later.

How would I do that? How would I encrypt, then later decrypt, a program using Visual C#.NET?

Answer 1

This answer shows you how to execute a byte array. One caution, this may cause problems with virus scanners because it is common in malware.

If you don’t want to execute from memory, I whipped up an example of how you could encrypt store then decrypt and run an executable.

 public class FileEncryptRunner
 {
    Byte[] key = ASCIIEncoding.ASCII.GetBytes("thisisakeyzzzzzz");
    Byte[] IV = ASCIIEncoding.ASCII.GetBytes("thisisadeltazzzz");

    public void SaveEncryptedFile(string sourceFileName)
    {
       using (FileStream fStream = new FileStream(sourceFileName, FileMode.Open, FileAccess.Read, FileShare.Read),
              outFStream = new FileStream(Environment.SpecialFolder.MyDocuments+"test.crp", FileMode.Create))
       {
          Rijndael RijndaelAlg = Rijndael.Create();
          using (CryptoStream cStream = new CryptoStream(outFStream, RijndaelAlg.CreateEncryptor(key, IV), CryptoStreamMode.Write))
          {
              StreamWriter sWriter = new StreamWriter(cStream);
              fStream.CopyTo(cStream);
          }
       }
    }

    public void ExecuteEncrypted()
    {
       using (FileStream fStream = new FileStream(Environment.SpecialFolder.MyDocuments + "test.crp", FileMode.Open, FileAccess.Read, FileShare.Read),
              outFStream = new FileStream(Environment.SpecialFolder.MyDocuments + "crpTemp.exe", FileMode.Create))
       {
          Rijndael RijndaelAlg = Rijndael.Create();
          using (CryptoStream cStream = new CryptoStream(fStream, RijndaelAlg.CreateDecryptor(key, IV), CryptoStreamMode.Read))
          {   //Here you have a choice. If you want it to only ever exist decrypted in memory then you have to use the method in
              // the linked answer.
              //If you want to run it from a file than it's easy and you save the file and run it, this is simple.                                               
              cStream.CopyTo(outFStream);
          }
       }
       Process.Start(Environment.SpecialFolder.MyDocuments + "crpTemp.exe");
    }
 }