From: Etienne Dechamps <etienne@edechamps.fr>
Date: Sun, 21 Sep 2014 17:17:02 +0000 (+0100)
Subject: Introduce node IDs.
X-Git-Tag: release-1.1pre11~38
X-Git-Url: https://tinc-vpn.org/git/browse?a=commitdiff_plain;h=55a78da4e0b496fc599704473f41d5ea52669737;hp=55a78da4e0b496fc599704473f41d5ea52669737;p=tinc

Introduce node IDs.

This introduces a new type of identifier for nodes, which complements
node names: node IDs. Node IDs are defined as the first 6 bytes of the
SHA-256 hash of the node name. They will be used in future code in lieu
of node names as unique node identifiers in contexts where space is at
a premium (such as VPN packets).

The semantics of node IDs is that they are supposed to be unique in a
tinc graph; i.e. two different nodes that are part of the same graph
should not have the same ID, otherwise things could break. This
solution provides this guarantee based on realistic probabilities:
indeed, according to the birthday problem, with a 48-bit hash, the
probability of at least one collision is 1e-13 with 10 nodes, 1e-11
with 100 nodes, 1e-9 with 1000 nodes and 1e-7 with 10000 nodes. Things
only start getting hairy with more than 1 million nodes, as the
probability gets over 0.2%.
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