How To Create A Password-Protected 7-Zip Archive In C# & .NET

In our previous post, How To Create A 7-Zip Archive In C# & .NET, we looked at how to create a 7z archive by automating the command line.

In this post, we will look at how to create a password-protected 7z archive.

Our project structure looks like this:

To ensure the Books folder is copied to the output, we add this element to the .csproj.

<ItemGroup>
  <None Include="Books\**\*">
  	<CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
  </None>
</ItemGroup>

The first order of business is to install the CliWrap library. This is orders of magnitude easier and more flexible than the native .NET Process class.

dotnet add package clirwap

The next order of business is that you need to know

1. The name of the 7-Zip executable
2. Where it is

In macOS (that I am using), the executable is actually named 7zz.

You can find out where it is using the where command.

where 7zz

If it is installed, the location will be printed.

For Windows, the executable is named 7z.exe, and is usually in the Program Files folder.

We now have enough to write the code.

using System.Reflection;
using CliWrap;
using CliWrap.Buffered;
using Serilog;

Log.Logger = new LoggerConfiguration()
    .WriteTo.Console().CreateLogger();

// Extract the current folder where the executable is running
var currentFolder = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location)!;

// Construct the full path to the source files
var folderWithBooks = Path.Combine(currentFolder, "Books");

// Construct the full path to the zip file
var target7ZipFile = Path.Combine(currentFolder, "Books.7z");

// Path to 7zip executable
const string executablePath = "/opt/homebrew/bin/7zz";

// Archive password
const string password = "A$tr0ngP@ssw0rD";

// Delete 7zip file if it exists
if (File.Exists(target7ZipFile))
    File.Delete(target7ZipFile);

// Orchestrate the command line to excute and run
var result = await Cli.Wrap(executablePath) // Set the path to the executable
  .WithArguments(args => args
  .Add("a") //Specify to create an archive
  .Add("-t7z") // Specify the target format - 7z
  .Add(target7ZipFile) // Taget file name
  .Add($"{folderWithBooks}//*") // The files in the source folder
  .Add($"-p{password}") // Set the password
  .Add("-mhe=on") // encrypt file names
  .Add("-mx=9") // max compression
  )
  .ExecuteBufferedAsync();

// Check if the process succeeded
if (result.ExitCode != 0)
    Log.Error("7-Zip failed: {Message}", result.StandardError);
else
    Log.Information("Written files in {SourceFiles} to {Target7ZipFile} : {Message}", folderWithBooks, target7ZipFile, result.StandardOutput);

The magic is taking place on these lines:

.Add($"-p{password}") // Set the password
.Add("-mhe=on") // encrypt file names

If we run this code, we should see the following:

The 7-Zip file is now in the output folder.

If we try to open the archive, we should see a password prompt.

TLDR

To create a password protected 7-Zip file, pass the password as an argument to the command-line tool.

The code is in my GitHub.

Happy hacking!