[bloodhand]

Someone from videohelp forum gave me the solution I already knew about: modify m3u8 to load a local key file instead of url, update every .ts part with full link and place the key file, m3u8 file and ffmpeg in the same folder, then issue -c copy command for that m3u8. But I don't know how he managed to get the key file, as entering key url in browser gives nothing.