Nodes are by design not supposed to be identifiable in any way, including
persisting identities across IPs changes or when connecting over different
networks (e.g. clearnet/tor). Anything that makes Bitcoin less private is a
step backwards. Also absolute node count is pretty meaningless since only
fully validating nodes that participate in economic activity really matter.

As a side note, this should probably have started out as a bitcoin-discuss
post.

On Sat, Mar 4, 2017 at 4:04 PM, John Hardy via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> The discussion of UASF got me thinking about whether such a method might
> lead to sybil attacks, with new nodes created purely to inflate the node
> count for a particular implementation in an attempt at social engineering.
>
> I had an idea for an anonymous, opt-in, unique node identification
> mechanism to help counter this.
>
> This would give every node the opportunity to create a node
> ‘address’/unique identifier. This could even come in the form of a Bitcoin
> address.
>
> The node on first installation generates and backs up a private key. The
> corresponding public key becomes that node’s unique identifier. If the node
> switches to a new software version or a new IP, the identifier can remain
> constant if the node operator chooses.
>
> Asking a node for its identifier can be done by sending a message the
> command ‘identify’ and a challenge. The node can then respond with its
> unique identifier and a signature for the challenge to prove it. The node
> can also include what software it is running and sign this information so
> it can be verified as legitimate by third parties.
>
> Why would we do this?
>
> Well, it adds a small but very useful piece of data when compiling lists
> of active nodes.
>
> Any register of active nodes can have a record of when a node identifier
> was “first seen”, and how many IPs the same identifier has broadcast from.
> Also, crucially, we could see what software the node operator has been seen
> running historically.
>
> This information would make it easy to identify patterns. For example if a
> huge new group of nodes appeared on the network with no history for their
> identifier they could likely be dismissed as sybil attacks. If a huge
> number of nodes that had been reporting as Bitcoin Core for an extended
> period of time started switching to a rival implementation, this would add
> credibility but not certainty (keys could be traded), that the shift was
> more organic.
>
> This would be trivial to implement, is (to me?) non-controversial, and
> would give a way for a node to link itself to a pseudo-anonymous identity,
> but with the freedom to opt-out at any time.
>
> Keen to hear any thoughts?
>
> Thanks,
>
> John Hardy
>
> john@seebitcoin.com
>
>
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>