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From: Gregory Maxwell <greg@xiph.org>
Date: Sat, 10 Sep 2016 00:42:30 +0000
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To: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
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Subject: [bitcoin-dev] Completing the retirement of the alert system
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The alert system was a centralized facility to allow trusted parties
to send messages to be displayed in wallet software (and, very early
on, actually remotely trigger the software to stop transacting).

It has been removed completely in Bitcoin Core after being disabled for a while.

While the system had some potential uses, there were a number of
problems with it.

The alert system was a frequent source of misunderstanding about the
security model and 'effective governance', for example a years ago a
BitcoinJ developer wanted it to be used to control fee levels on the
network and few months back one of Bloq's staff was pushing for a
scheme where "the developers" would use it to remotely change the
difficulty-- apparently with no idea how abhorrent others would find
it.

The system also had a problem of not being scalable to different
software vendors-- it didn't really make sense that core would have
that facility but armory had to do something different (nor would it
really make sense to constantly have to maintain some list of keys in
the node software).

It also had the problem of being unaccountable. No one can tell which
of the key holders created a message. This creates a risk of misuse
with a false origin to attack someone's reputation.

Finally, there is good reason to believe that the key has been
compromised-- It was provided to MTGox by a developer and MTGox's
systems' were compromised and later their CEO's equipment taken by the
Japanese police.

In any case, it's gone now in Core and most other current software--
and I think it's time to fully deactivate it.

I've spent some time going around the internet looking for all
software that contains this key (which included a few altcoins) and
asked them to remove it. I will continue to do that.

One of the facilities in the alert system is that you can send a
maximum sequence alert which cannot be overridden and displays only a
static key compromise text message and blocks all other alerts. I plan
to send a triggering alert in the not-distant future (exact time to be
announced well in advance) feedback on timing would be welcome.

There are likely a few production systems that automatically shut down
when there is an alert, so this risks some small one-time disruption
of those services-- but none worse than if an alert were sent to
advise about a new system upgrade.

At some point after that, I would then plan to disclose this private
key in public, eliminating any further potential of reputation attacks
and diminishing the risk of misunderstanding the key as some special
trusted source of authority.

Cheers,