Bitcoin Forum

Summary

The network wide Alert system is being retired. No Bitcoins are at risk and this warning may be safely ignored.
Upgrade to the newest version of your wallet software to no longer see the alert.

Reasons for Retirement

The network wide Alert system was created by Satoshi Nakamoto as a means of informing Bitcoin users of any important
information regarding Bitcoin. It has been used in the past to inform users about important network events such as
accidental blockchain forks. However, the Alert system also represents a large source of centralization in Bitcoin.
The holders of the singular Alert Key can at any time send an alert which could affect the entire network. As more
developers join, the Alert Key is given to others, but cannot be taken away from those who have left. This has led
to the Alert Key potentially falling into the hands of malicious actors who could use it to disrupt the network. Because
there is only one Alert key, it is not possible to prevent former developers from sending an alert nor is it possible
to identify who sent an Alert.

In addition, the Alert system is primarily Bitcoin Core specific. Many other wallets have their own systems in place but
still must have handling for the Alert system because it is network wide. Something specific for one software should
not be imposed on the entire network.

The Alert system has also lost its usefulness. It is no longer necessary to use it to inform users about problematic network
events as users can easily get their information from any major Bitcoin news outlet.

The Retirement Plan

Retirement of the Alert system consists of a pre-final alert (this alert) which will warn about the impending retirement, a
final maximum sequence alert which cannot be overridden and displays a static "Alert Key Compromised" message, and the
publishing of the Alert key itself. The final alert will be hard coded into Bitcoin Core 0.14 to ensure that all old nodes
receive the final alert.

Action	Description	Date
Pre-final Alert Posts	Posts on Bitcoin.org, various forums, and various mailing lists that the Alert system will be retired	2016-11-01
Pre-final Alert	The alert itself warning that the Alert system will be retired	2016-11-02
Final Alert	Max sequence Alert to disable the Alert system	2017 (Will coincide with Bitcoin Core 0.14 Release Candidate process)
Alert key released	The Alert key will be made publicly available	1-2 months after the Final Alert

Software without the Alert system

Most major Bitcoin wallets have already removed the alert system in the most recent releases. The software listed below
are guaranteed to have removed/disabled the Alert system or allow you to disable it.

• Bitcoin Core 0.13.1, 0.13.0, 0.12.1
• Bitcoin Core 0.10.3, 0.11.x, and 0.12.x can disable alerts with `-alerts=0`
• Armory 0.94.1+

See also

Original email proposing retirement (https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2016-September/013104.html)
Pull request removing Alert system (https://github.com/bitcoin/bitcoin/pull/7692)
Removal discussion on github (https://github.com/bitcoin/bitcoin/pull/6260)
Pull request disabling alerts (https://github.com/bitcoin/bitcoin/pull/6274)
IRC Discussion (https://botbot.me/freenode/bitcoin-core-dev/2016-09-22/?msg=73446303&page=6)

Is there any new alert-system replacing the old one, or was the entire idea of alerting users in case of emergency deemed as unnecessary?

I didn't even know there was an alert system. I guess you learn something new every day haha  :). Thanks achow101 for the helpful tips.

I don't remember ever seeing an alert and I have been using Bitcoin Core since it was called Bitcoin QT around version 0.7... I wonder how the alert looked like. Is this orange square message an alert?

That's interesting, it's good to know that the alert key being in the hands of a few is supporting centralization and indirectly affecting the entire network by spreading some form of news. Also, I was wondering why give out the Alert key to the public? Is there any benefit for us from it or is it being done just to support decentralization?

Would be nice to know how the alert system works on Bitcoin core, I was assuming it was the alert system on Bitcoin.org's website towards the top.

It's being done to support decentralization and to actually kill off the alert system. By releasing the key, the system is completely discredited.

I also thought about asking that very question. Does it make any sense to release the key beyond making the retired system completely "discredited"? Why would developers need to do that at all? What kind of pain in the ass makes them want to "discredit the system"? Are they seeking revenge on someone or what? If the system is dismantled completely, then giving out the public key is technically irrelevant, but if it is not and somehow it is still valid and active, it might wreak havoc.

The system will be sufficiently dead by the time that the key is released. A maximum sequence alert cannot be overridden. Bitcoin Core 0.14 will be constantly broadcasting that final alert so that all nodes receive it by the time the hey is released.

But what is the real purpose of giving out the key? I remember a time when the Linux iptables had a feature that allowed to send back the offending packets to the source (it was called MIRROR or something to that tune, if I'm not mistaken), but it got soon removed since that had been a silly idea right from the start. Why not just abandon this Alert system without making it look like a personal vendetta?

It somehow feels wrong to undo Satoshi's master plan to inform users when major events happens, but I can see how some people might misuse

this system, if they cannot be properly removed. I was under the impression Gavin's key was removed and he could not access that system... or do

they mean that a rogue developer might try to sabotage Bitcoin whilst he or she still has the key? Well I hope there are a good replacement that can

be properly verified with a PGP key.  ::)

I guess they give out the key to demonstrate that the key is useless after they remove the alert system.

But what is the real purpose of giving out the key? I remember a time when the Linux iptables had a feature that allowed to send back the offending packets to the source (it was called MIRROR or something to that tune, if I'm not mistaken), but it got soon removed since that had been a silly idea right from the start. Why not just abandon this Alert system without making it look like a personal vendetta?

What I don't get is... wouldn't the key will still be useful to trigger alerts in the pre 0.13 software??

It somehow feels wrong to undo Satoshi's master plan to inform users when major events happens, but I can see how some people might misuse

this system, if they cannot be properly removed. I was under the impression Gavin's key was removed and he could not access that system... or do

they mean that a rogue developer might try to sabotage Bitcoin whilst he or she still has the key? Well I hope there are a good replacement that can

be properly verified with a PGP key.  ::)

This is the "official version", which is meaningless, in my view. And it is a childish act as well since this key was not intended to be made public in the first place, as I got it.

To further clarify my point, would the developers want to release the old inactive key if they decided just to change it, for whatever reason (let's assume that it is possible to change the key)?

Would you believe them if they said they would release it to the public to demonstrate that the old key is no longer useful?

Yes, I would want the developers to release the old inactive key if they changed. If they changed the key, they would follow a process very similar to what is being done now; the developers aren't stupid and do think of the consequences. They would have the max sequence alert broadcast to have the "Alert key compromised". The next version of the software would have that same alert hard coded and continuously broadcast to make sure all old nodes get the message. That new release would also have the new key, or, in this case, no key and the whole thing gone.

Now all we need is to find out if the Alert key has ever been changed. If it hasn't been, then there is no evidence as to what might have happened, then let's call it a day, for the lack of evidence, obviously. If they changed the key and disclosed the old one, that would mean one thing, but if they changed it and didn't disclose the old key, that would mean something totally different, right?

The key has never been changed. You can follow the commits in the git tree. The only change to it has been its removal.

Read the last paragraph of this email: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2016-September/013104.html

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.

I still don't understand two things. 1) what further potential reputation attacks are possible,

and 2) which seems to me the most important here, wasn't the key exactly that? I mean, a special trusted source of authority? Regarding the first, just mentioning further reputation attacks is already telling a lot by itself. Regarding the second, I think just because the key was available only to a few core developers and due to the fact that it served a special purpose of alerting users, it implies that it should have been trusted and authoritative. Otherwise, it couldn't function as a true Alert key as far as I get it.

So the thinking goes: if the key is still held secret after the alert system is dead, people may still think that it holds some special importance and can still be used as a centralizing trusted authority. The goal is to avoid this and to kill off any significance the key may have by publishing it publicly.

That makes sense provided that this key is the key. But really paranoid people could still claim that the key disclosed has nothing to do with the real Alert key, or whatever else it might have been used for. And because the whole system will already be dismantled by the time the key is released to the public, it won't be possible to check that. Maybe, I'm missing something here, and there are ways to actually prove the authenticity of the key even if the system has already been removed from Bitcoin. I just don't know, that's why I'm asking.

I think what reputation attacks mean is, somebody that has a reputation in the bitcoin ecosystem (like Gavin Andressen for example) could use their key to push a certain agenda.

If nobody has the key, then nobody can do that sort of attack anymore.

Yes, in fact it is possible to check the authenticity of the key. The public key was hard coded into the software. You can still go back in the git tree and find the commits where the key was in the code. The private key for the public key will be released. That public key for the private key can be derived and checked to see if it matches the public key that was hard coded. Here is one place the alert public key is hard coded: https://github.com/bitcoin/bitcoin/blob/0.12/src/chainparams.cpp#L104 That is the 0.12 branch of Bitcoin Core.

Ahh. Yes, I did not think of that. Someone who holds the key could sign a message and post it somewhere claiming something which could be bad for Bitcoin. Because the key would still be held privately, the person who made that message could claim that the core devs want people to follow the signed message because people may think the key still holds some significance. By revealing the key publicly, this potential attack vector is completely removed.

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