Two more uses of information entropy metric

Downloading torrent files

Using 'binwalk -E' or 'binwalk -E -F', you can easily see which blocks of a torrent file are already downloaded, and which are zero/empty blocks...

As of high-entropy music and video files, you can quickly see if it was downloaded fully, without zero blocks remained.

A real example: binwalk output and what qBittorrent shows.

I really do this when I find some (maybe (un)-finished) video file in Downloads directory.

Also, an archiver (like 7z, RAR, ZIP) can skip high-entropy files (because they are already uncompressable) to increase archiving speed. (Entropy can be measured quickly by small random spots in file.)

A more sophisticated compressor (like gzip, bzip, xz) can detect high-entropy spots in a file and skip them.

(the post first published at 20251110.)

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