I recently worked on a project that involved creating encrypted zip files. Data is captured on a web form and then written to a text file. At first, the task sounded complex. However, if you are aware of the DotNetZip library existence, your task just got easier.
You can download the
DotNetZip library from here. Once you download and install the package, you will need to add a reference to Ionic.Zip.dll or copy the file to your \lib folder. This is all you need to start generating your own zip files.
The best part:
DotNetZip is free!!
DotNetZip is well documented and is much easier to use than any other solutions out there including
System.IO.Compression and SharpZipLib. After trying both methods, I would highly recommend
DotNetZip because is incredibly easy to use.
Below is a sample method to illustrate how to easily compress content that is being passed as a
string. The method takes the file name and the content as arguments:
internal MemoryStream ZipString(string aZipFileName, string aContents, string aMode)
string sZipFilePassword = ConfigurationManager.AppSettings["ZipFilePassword"];
string sZipFileEncryption = ConfigurationManager.AppSettings["ZipFileStrongEncryption"];
MemoryStream msZippedContent = new MemoryStream();
using (var zip = new ZipFile())
zip.Password = sZipFilePassword;
if (sZipFileEncryption == "N")
zip.Encryption = EncryptionAlgorithm.PkzipWeak;
zip.Encryption = EncryptionAlgorithm.WinZipAes256;
zip.AddEntry(aZipFileName, aContents, Encoding.ASCII);
catch (Exception genEx)
The method declares a variable of type
ZipFile which is available once you add a reference: "
using Ionic.Zip;" That declaration creates the shell of the zip file. After that, the process to save the file is simple, add a password if needed, add an encryption method and you can proceed to add an entry to the zip file by using
AddEntry. Of course, you could add multiple files to the same zip archive. Finally, you can save the contents of the zip which in this case are returned by the method as a
MemoryStream that could be used for other purposes such as creating an e-mail attachment.
Be aware that if you need to encrypt the contents of the zip, choosing the encryption method is important because the built-in Windows unzip feature can only decrypt
PkZip.Weak content. You would need to have WinZip or WinRar Installed on the target workstation to unzip contents encrypted with the
Hope this is helpful. Feel free to contact me if you have any questions.