Security Feature: Error if local / repository nonce are not in agreement -- improve encryption trust about borg HOT 1 CLOSED

The local and server nonce can be easily out of sync, e.g. if you back up with 2 different clients to same repo. Or if you run borg commands on the server also (which would make it client also).

The solution for this will come in borg2, which does not need nonce management any more, because it just uses new session keys for each borg invocation.

Also, I suggest trying the nonce behaviour with borg 1.x practically. The problematic case is if the server suggests an older / lower nonce value than it should (and than the client usually knows locally also) - that would lead to nonce reuse IF the borg client would take that value (which it does not if the local value is higher). IIRC, borg already complains loudly in that case and rejects to work with the repo.

from borg.