Password-protecting a ZIP archive involves adding a password to the archive to secure its contents. This ensures that only individuals with the correct password can extract or access the files within the ZIP archive. This password acts as a form of encryption, preventing unauthorized access to the files stored in the archive. To extract files from a password-protected ZIP archive, users must enter the correct password.

Create an empty ZIP file or open an existing one. Inside the 'using' statement, use the Encrypt method to apply a password. The Encrypt method supports traditional passwords, which can be opened by the Windows' built-in extractor. This method also supports AES128 and AES256-based password encryption; however, these two password types cannot be opened with Windows' built-in extractor and require third-party tools such as WinRar and 7Zip.