[Standards] hash agility in file transfer

Waqas Hussain waqas20 at gmail.com
Thu Jun 2 03:02:42 UTC 2011

On Thu, Jun 2, 2011 at 4:00 AM, Glenn Maynard <glenn at zewt.org> wrote:
> It should be specified explicitly that the hash is of the complete
> file, even when only a range is being offered.

Note that a specific range isn't offered. Only generic support for
ranges is advertised. So the hash can only be of the complete file.

What HTTP does is relevant here. The "Content-MD5" HTTP header applies
to the current payload being transferred, not the whole file. But
given that this XEP defines an offer-accept protocol, initiated by the
file sender (as opposed to a request-response protocol initiated by
the file recipient), it isn't possible to verify range transfers.

There is actually quite an interesting use-case: There are download
managers which can download partial content from inside a large
archive. All they need to do is retrieve the archive index (e.g., zip
files have an index at the end), and then request relevant portion(s)
of the archive with the content of interest.

> --
> Glenn Maynard

Waqas Hussain

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