Surprisingly, 10 years after Bitcoin’s creation, most people still don’t know the correct answer to this question:
I assure you, there is a single correct answer.
Understanding of Bitcoin behaves like a moving target while we are still in the early adoption phase. It takes years to understand Bitcoin, and we get new Bitcoiners every day. Veterans become complacent and impatient when it comes to repeating lessons learned and frustrations are piled on due to constant attacks from disinformants and delusionists.
So, instead of repeating ourselves over and over to every new entrant, I have written this post as a reference for posterity. Although I’m sure the concepts exist elsewhere, and I doubt this rationale is new, it took me seven years to distill these concepts into simple non-technical terms.
What is security?
Before sorting out who secures Bitcoin, let’s agree on what “security” actually means in this context. Keeping Bitcoin secure means maintaining confidence on what Bitcoin is.
What is Bitcoin?
You’ll get the wildest answers if you ask this question, but the truth is so simple and boring that people see right past it.
Bitcoin is a store of value and a protocol for managing the rights to which keys can transfer control of that value.
When I say “store of value” I mean that in the literal sense! We are literally assigning a numerical value to an account number. It doesn’t even matter whether we all agree to use that value as money or internet points or as an anchor for external taint.
In its simplest form, think of Bitcoin as a spreadsheet with two columns: Keys, and Value
What does it mean to secure Bitcoin?
Well, it means to confirm that we agree on what Bitcoin is. Securing Bitcoin means reaching consensus on the information in the database, and agreement on the processes used for altering that database.
Securing Bitcoin is achieving consensus on the database and the protocol used for changing it.
What is consensus?
Consensus is when all players agree on who owns what. You see, Bitcoin isn’t actually immutable in strict terms. If it were, we wouldn’t need the protocol or miners at all. The protocol exists to define what the rules are for changing the value store. The immutable part is just an audit history of proof that past changes followed consensus rules.
So, who secures Bitcoin?!
If securing Bitcoin requires consensus on what Bitcoin is, and Bitcoin is a database of values assigned to keys, and Bitcoin has a protocol for reassignment of keys, then securing Bitcoin can only be done by … your node!
Nodes! Nodes! Nodes!
In the end, YOU secure Bitcoin, but the only time that matters is when you agree with someone else on what Bitcoin is, and the only way that you can express yourself to others is via your node.
You can try to abstract this and say that hodlers of last resort secure it, or that you can express yourself by buying or selling, but the only way you can actually communicate yourself is via enforcement of the protocol.
What about Miners?
Miners are suppliers of blocks, nothing more. Nodes demand consensus-compatible blocks as a vessel for key reassignment. Miners’ ability to influence the protocol is limited to the wiggle room within the protocol’s magic numbers.
For example, they can limit blocksize if they can cooperate and coordinate over shared incentives, and they can exclude transactions in the same way. But when a miner exercises any power that is detrimental to consensus they approach high risks at a quick pace.
This same dynamic applies to re-orgs, 51% attacks, etc. These attacks are not only risks to miners in that there is a cost in sacrificing blocks or failing probabilities, they run the higher-level risk of being entirely ignored and excluded from extra-protocol consensus, the market itself.
Nodes actually define what a “miner” is.
Miners propose blocks containing new key reassignments, and mining (proof of work) is the scheme designed for creating a reliable marketplace for the current cost of that opportunity.
Miners secure nothing but their own relationship to Bitcoin, all miner attack and failure modes can be transcended by node consensus.
What about Devs?
Many respondents to the poll above think all 3 are needed for security: Miners, Nodes, Devs. However, Bitcoin protocol developers, and miners, are actually adversaries to consensus!
But, John, they fix bugs! They scale Bitcoin!
Sure, they help Bitcoiners out a lot, in practice, by adding optimizations and support for features and new key-schemes that leverage Bitcoin’s qualities. But all actors seeking to change Bitcoin in any way are indistinguishable from attackers, without consensus.
The only way to achieve consensus and communicate what you think Bitcoin is, is with your node.
All nodes are not equal.
It’s not enough to run a node and express your consensus. In the end, only nodes with skin in the game will enforce a definition of Bitcoin that is valuable to them.
This gets into the concept of an “economic node”, a term which attempts to capture the concept of a player in the Bitcoin game who has attributed external value to his BTC and is representing real risk burden as an economic actor on the network.
A non-economic node is an unreliable signal of consensus.
What is an economic node?
Basically, if you do not have BTC exposure to secure, you have nothing to enforce, thus no significant incentive to act within consensus.
Specifically, an economic node is one that has transactions to verify. When the network confirms your key reassignments, you are creating and receiving reliable signals of consensus.