Create ZipFile with password without external libraries C#

As the title says, I need to create a zip file secured with a given password but I have the constraint of don’t use any external library. I have to use only .NET Framework 4.6.1

Currently, I’m creating the file using System.IO.Compression and the code is this:

using (MemoryStream zipStream = new MemoryStream())
{
     using (ZipArchive zipFile = new ZipArchive(zipStream, ZipArchiveMode.Create, false))
     {
          foreach (InlineContent report in reports)
          {
               ZipArchiveEntry zipEntry = zipFile.CreateEntry(report.FileName, CompressionLevel.Optimal);
               using (StreamWriter writer = new StreamWriter(zipEntry.Open()))
               {
                    new MemoryStream(report.Content.ToArray()).WriteTo(writer.BaseStream);
               }
          }
     }
}

This is how I’m generating the file, not how I save it. I understand that it’s not relevant for this put that part of the code.

If someone can help me with this I would be very thankful.

>Solution :

You can’t. There is a issue asking to add the password support into standard ZipArchive class and the issue is still open: https://github.com/dotnet/runtime/issues/1545

So, the only way to support passwords without using the 3rd-party libraries will be to implement zip format with password support from scratch manually and use this implementation instead of ZipArchive. I don’t think it is possible to elaborate the all details of such an implementation in the SO answer, but you can definitely check out the sources of the existing 3rd-party libraries for reference.