This only performs some basic tests so far; no testing of chunking or
resuming. Also, the existing encryption type of the remote is used; it
would be good later to derive an encrypted and a non-encrypted version of
the remote and test them both.
This commit was sponsored by Joseph Liu.
Needed for resuming from chunks.
Url keys are considered not stable. I considered treating url keys with a
known size as stable, but just don't feel that is enough information.
Note that the hash backends were made to stop printing a (checksum..)
message as part of this, since it showed up without a file when deciding
whether to act on a file. Should have probably removed that message a while
ago anyway, I suppose.
SHA3 is still waiting for final standardization.
Although this is looking less likely given
https://www.cdt.org/blogs/joseph-lorenzo-hall/2409-nist-sha-3
In the meantime, cryptohash implements skein, and it's used by some of the
haskell ecosystem (for yesod sessions, IIRC), so this implementation is
likely to continue working. Also, I've talked with the cryprohash author
and he's a reasonable guy.
It makes sense to have an alternate high security hash, in case some
horrible attack is found against SHA2 tomorrow, or in case SHA3 comes out
and worst fears are realized.
I'd also like to support using skein for HMAC. But no hurry there and
a new version of cryptohash has much nicer HMAC code, so I will probably
wait until I can use that version.
