Make --checksum work with crypt remotes

[ncw (Nick Craig-Wood)]

But after a second thought: why don’t we encrypt the files locally for the only purpose of computing a check sum, and compare this to the remote checksum?

Cryptcheck does exactly this.

The upload process does too - so it computes a hash of the data that is being read and at the end of the upload compares it to the hash produced by the remote end thus making a very strong integrity check.