If it *is* portable, it might seem a better choice for archives over
tar, simply because more systems these days can handle zip files than
can handle tar files...
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Writing a program to unpack a tar archive is not difficult.
The problem I see with zip is the single table of contents at the end.
Did you try corrupting THAT with a hex editor?
The file headers in a tar archive appear in front of each file. It is
generally possible to resync after errors in the decoding stream.