Check whether a zip file is protected by password in Objective-C/iPhone?

I'm using lib ZipArchive to unzip file on iPhone, it works pretty well, however I met a issue about checking if a zip file is protected by password.

I'm wondering if there's a function to check whether a zip file i开发者_开发问答s protected by password before unzipping, but I didn't get lucky to find an api for that. So does anyone who know how to check it in Objective-C/iPhone or any API in ZipArchive I can use.

Any help would be greatly appreciated.

You can check central directory in archive, and see if encryption bit is set there. However, you will need to read some documentation regarding zip file format.