DRM events are not fired on iOS

I have a video player which plays encrypted FLV files. Here is related piece of the code

    stream.addEventListener(StatusEvent.STATUS, onStatusEvent);

    stream.addEventListener(DRMStatusEvent.DRM_STATUS, onDRMStatus);

    stream.addEventListener(DRMErrorEvent.DRM_ERROR, onDRMError);

    stream.addEventListener(DRMAuthenticateEvent.DRM_AUTHENTICATE, onDRMAuthenticate);

It works fine on Android, Windows and Mac, but for whatever reason on iOS onStatusEvent, onDRMAuthenticate or onDRMError are never fired, and the file is not played.

iPad Mini, iOS 7.0.4, Adobe AIR SDK 3.9.

Files are in FLV format, codec On2 VP6 (not H.264), so those events should be supported.

Here is the FLV example: http://www.scienceofmassage.com/dnn/som/protocols/library/bell/bell_01.flv

Any help is greatly appreciated.