Remove digital signature from a file using C#
There are two reasons why you might want to consider removing the digital signature from some of the files you are using, especially third party libraries.
The first reason is because in many cases it will greatly speed up your programs start-up time. The reason for that is because if a file is signed with Microsoft digital certificate as an example on runtime it will attempt to verify the signature which in most cases it requires an internet connection. In cases where the user might not have an active internet connection or if the verification attempt is blocked by a firewall or any other reason, it will greatly increase the time your application will take to start.
Another important reason for removing a digital signature from a library you want to distribute alongside with your software is that a lot of users feel alarmed when an application tries to establish a connection at start-up, especially if the type of the application you are making doesn’t sound like the type it requires to connect somewhere.
Thankfully it is fairly easy to remove a signature from a file using the ImageRemoveCertificate API function. Below you can find a snippet that illustrates how it can be implemented.
1 2 | [System.Runtime.InteropServices.DllImport("Imagehlp.dll ")] private static extern bool ImageRemoveCertificate(IntPtr handle, int index); |
1 2 3 4 5 6 7 8 | private void UnsignFile(string file) { using (System.IO.FileStream fs = new System.IO.FileStream(file, System.IO.FileMode.Open, System.IO.FileAccess.ReadWrite)) { ImageRemoveCertificate(fs.SafeFileHandle.DangerousGetHandle(), 0); fs.Close(); } } |
If you would like to use the above code but have no knowladge on how to compile it then simply download the already compiled version from FileUnsigner v1.0.
Don’t use index 0 for ImageRemoveCertificate(). Get its value from ImageEnumerateCertificates() API.
I’m using 0 and its working.
Can you give a code example?
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