The quantum computing debate is heating up. There are many controversial aspects to this debate,
including whether or not quantum computers will ever actually become a practical threat.
I won't tread into the unanswerable question of how worried we should be about quantum computers. I
think it's far from a crisis, but given the difficulty in changing Bitcoin it's worth starting to
seriously discuss. Today I wish to focus on a philosophical quandary related to one of the decisions
that would need to be made if and when we implement a quantum safe signature scheme.
Several Scenarios
Because this essay will reference game theory a fair amount, and there are many variables at play
that could change the nature of the game, I think it's important to clarify the possible scenarios
up front.
1. Quantum computing never materializes, never becomes a threat, and thus everything discussed in
this essay is moot.
2. A quantum computing threat materializes suddenly and Bitcoin does not have quantum safe
signatures as part of the protocol. In this scenario it would likely make the points below moot
because Bitcoin would be fundamentally broken and it would take far too long to upgrade the
protocol, wallet software, and migrate user funds in order to restore confidence in the network.
3. Quantum computing advances slowly enough that we come to consensus about how to upgrade Bitcoin
and post quantum security has been minimally adopted by the time an attacker appears.
4. Quantum computing advances slowly enough that we come to consensus about how to upgrade Bitcoin
and post quantum security has been highly adopted by the time an attacker appears.
For the purposes of this post, I'm envisioning being in situation 3 or 4.
To Freeze or not to Freeze?
I've started seeing more people weighing in on what is likely the most contentious aspect of how a
quantum resistance upgrade should be handled in terms of migrating user funds. Should quantum
vulnerable funds be left open to be swept by anyone with a sufficiently powerful quantum computer OR
should they be permanently locked?
"I don't see why old coins should be confiscated. The better option is to
let those with quantum
computers free up old coins. While this might have an inflationary impact
on bitcoin's price, to
use a turn of phrase, the inflation is transitory. Those with low time
preference should support
returning lost coins to circulation."
- Hunter Beast
On the other hand:
"Of course they have to be confiscated. If and when (and that's a big if)
the existence of a
cryptography-breaking QC becomes a credible threat, the Bitcoin ecosystem
has no other option
than softforking out the ability to spend from signature schemes (including
ECDSA and BIP340)
that are vulnerable to QCs. The alternative is that millions of BTC become
vulnerable to theft;
I cannot see how the currency can maintain any value at all in such a
setting. And this affects
everyone; even those which diligently moved their coins to PQC-protected
schemes."
- Pieter Wuille
I don't think "confiscation" is the most precise term to use, as the funds are not being seized and
reassigned. Rather, what we're really discussing would be better described as "burning" - placing
the funds *out of reach of everyone*.
Not freezing user funds is one of Bitcoin's inviolable properties. However, if quantum computing
becomes a threat to Bitcoin's elliptic curve cryptography, *an inviolable property of Bitcoin will
be violated one way or another*.
Fundamental Properties at Risk
5 years ago I attempted to comprehensively categorize all of Bitcoin's fundamental properties that
give it value. https://nakamoto.com/what-are-the-key-properties-of-bitcoin/
<https://nakamoto.com/what-are-the-key-properties-of-bitcoin/>
The particular properties in play with regard to this issue seem to be:
*Censorship Resistance* - No one should have the power to prevent others from using their bitcoin or
interacting with the network.
*Forward Compatibility* - changing the rules such that certain valid transactions become invalid
could undermine confidence in the protocol.
*Conservatism* - Users should not be expected to be highly responsive to system
issues.
As a result of the above principles, we have developed a strong meme (kudos to Andreas Antonopoulos)
that goes as follows:
Not your keys, not your coins.
I posit that the corollary to this principle is:
Your keys, only your coins.
A quantum capable entity breaks the corollary of this foundational principle. We secure our bitcoin
with the mathematical probabilities related to extremely large random numbers. Your funds are only
secure because truly random large numbers should not be guessable or discoverable by anyone else in
the world.
This is the principle behind the motto /vires in numeris/ - strength in numbers. In a world with
quantum enabled adversaries, this principle is null and void for many types of cryptography,
including the elliptic curve digital signatures used in Bitcoin.
Who is at Risk?
There has long been a narrative that Satoshi's coins and others from the Satoshi era of P2PK locking
scripts that exposed the public key directly on the blockchain will be those that get scooped up by
a quantum "miner." But unfortunately it's not that simple. If I had a powerful quantum computer,
which coins would I target? I'd go to the Bitcoin rich list and find the wallets that have exposed
their public keys due to re-using addresses that have previously been spent from. You can easily
find them at https://bitinfocharts.com/top-100-richest-bitcoin-addresses.html <https://
bitinfocharts.com/top-100-richest-bitcoin-addresses.html>
Note that a few of these wallets, like Bitfinex / Kraken / Tether, would be slightly harder to crack
because they are multisig wallets. So a quantum attacker would need to reverse engineer 2 keys for
Kraken or 3 for Bitfinex / Tether in order to spend funds. But many are single signature.
Point being, it's not only the really old lost BTC that are at risk to a quantum enabled adversary,
at least at time of writing. If we add a quantum safe signature scheme, we should expect those
wallets to be some of the first to upgrade given their incentives.
The Ethical Dilemma: Quantifying Harm
Which decision results in the most harm?
By making quantum vulnerable funds unspendable we potentially harm some Bitcoin users who were not
paying attention and neglected to migrate their funds to a quantum safe locking script. This
violates the "conservativism" principle stated earlier. On the flip side, we prevent those funds
plus far more lost funds from falling into the hands of the few privileged folks who gain early
access to quantum computers.
By leaving quantum vulnerable funds available to spend, the same set of users who would otherwise
have funds frozen are likely to see them stolen. And many early adopters who lost their keys will
eventually see their unreachable funds scooped up by a quantum enabled adversary.
Imagine, for example, being James Howells, who accidentally threw away a hard drive with 8,000 BTC
on it, currently worth over $600M USD. He has spent a decade trying to retrieve it from the landfill
where he knows it's buried, but can't get permission to excavate. I suspect that, given the choice,
he'd prefer those funds be permanently frozen rather than fall into someone else's possession - I
know I would.
Allowing a quantum computer to access lost funds doesn't make those users any worse off than they
were before, however it /would/ have a negative impact upon everyone who is currently holding bitcoin.
It's prudent to expect significant economic disruption if large amounts of coins fall into new
hands. Since a quantum computer is going to have a massive up front cost, expect those behind it to
desire to recoup their investment. We also know from experience that when someone suddenly finds
themselves in possession of 9+ figures worth of highly liquid assets, they tend to diversify into
other things by selling.
Allowing quantum recovery of bitcoin is /tantamount to wealth redistribution/. What we'd be allowing
is for bitcoin to be redistributed from those who are ignorant of quantum computers to those who
have won the technological race to acquire quantum computers. It's hard to see a bright side to that
scenario.
Is Quantum Recovery Good for Anyone?
Does quantum recovery HELP anyone? I've yet to come across an argument that it's a net positive in
any way. It certainly doesn't add any security to the network. If anything, it greatly decreases the
security of the network by allowing funds to be claimed by those who did not earn them.
But wait, you may be thinking, wouldn't quantum "miners" have earned their coins by all the work and
resources invested in building a quantum computer? I suppose, in the same sense that a burglar earns
their spoils by the resources they invest into surveilling targets and learning the skills needed to
break into buildings. What I say "earned" I mean through productive mutual trade.
For example:
* Investors earn BTC by trading for other currencies.
* Merchants earn BTC by trading for goods and services.
* Miners earn BTC by trading thermodynamic security.
* Quantum miners don't trade anything, they are vampires feeding upon the
system.
There's no reason to believe that allowing quantum adversaries to recover vulnerable bitcoin will be
of benefit to anyone other than the select few organizations that win the technological arms race to
build the first such computers. Probably nation states and/or the top few largest tech companies.
One could certainly hope that an organization with quantum supremacy is benevolent and acts in a
"white hat" manner to return lost coins to their owners, but that's incredibly optimistic and
foolish to rely upon. Such a situation creates an insurmountable ethical dilemma of only recovering
lost bitcoin rather than currently owned bitcoin. There's no way to precisely differentiate between
the two; anyone can claim to have lost their bitcoin but if they have lost their keys then proving
they ever had the keys becomes rather difficult. I imagine that any such white hat recovery efforts
would have to rely upon attestations from trusted third parties like exchanges.
Even if the first actor with quantum supremacy is benevolent, we must assume the technology could
fall into adversarial hands and thus think adversarially about the potential worst case outcomes.
Imagine, for example, that North Korea continues scooping up billions of dollars from hacking crypto
exchanges and decides to invest some of those proceeds into building a quantum computer for the
biggest payday ever...
Downsides to Allowing Quantum Recovery
Let's think through an exhaustive list of pros and cons for allowing or preventing the seizure of
funds by a quantum adversary.
Historical Precedent
Previous protocol vulnerabilities weren’t celebrated as "fair game" but rather were treated as
failures to be remediated. Treating quantum theft differently risks rewriting Bitcoin’s history as a
free-for-all rather than a system that seeks to protect its users.
Violation of Property Rights
Allowing a quantum adversary to take control of funds undermines the fundamental principle of
cryptocurrency - if you keep your keys in your possession, only you should be able to access your
money. Bitcoin is built on the idea that private keys secure an individual’s assets, and
unauthorized access (even via advanced tech) is theft, not a legitimate transfer.
Erosion of Trust in Bitcoin
If quantum attackers can exploit vulnerable addresses, confidence in Bitcoin as a secure store of
value would collapse. Users and investors rely on cryptographic integrity, and widespread theft
could drive adoption away from Bitcoin, destabilizing its ecosystem.
This is essentially the counterpoint to claiming the burning of vulnerable funds is a violation of
property rights. While some will certainly see it as such, others will find the apathy toward
stopping quantum theft to be similarly concerning.
Unfair Advantage
Quantum attackers, likely equipped with rare and expensive technology, would have an unjust edge
over regular users who lack access to such tools. This creates an inequitable system where only the
technologically elite can exploit others, contradicting Bitcoin’s ethos of decentralized power.
Bitcoin is designed to create an asymmetric advantage for DEFENDING one's wealth. It's supposed to
be impractically expensive for attackers to crack the entropy and cryptography protecting one's
coins. But now we find ourselves discussing a situation where this asymmetric advantage is
compromised in favor of a specific class of attackers.
Economic Disruption
Large-scale theft from vulnerable addresses could crash Bitcoin’s price as quantum recovered funds
are dumped on exchanges. This would harm all holders, not just those directly targeted, leading to
broader financial chaos in the markets.
Moral Responsibility
Permitting theft via quantum computing sets a precedent that technological superiority justifies
unethical behavior. This is essentially taking a "code is law" stance in which we refuse to admit
that both code and laws can be modified to adapt to previously unforeseen situations.
Burning of coins can certainly be considered a form of theft, thus I think it's worth
differentiating the two different thefts being discussed:
1. self-enriching & likely malicious
2. harm prevention & not necessarily malicious
Both options lack the consent of the party whose coins are being burnt or transferred, thus I think
the simple argument that theft is immoral becomes a wash and it's important to drill down into the
details of each.
Incentives Drive Security
I can tell you from a decade of working in Bitcoin security - the average user is lazy and is a
procrastinator. If Bitcoiners are given a "drop dead date" after which they know vulnerable funds
will be burned, this pressure accelerates the adoption of post-quantum cryptography and strengthens
Bitcoin long-term. Allowing vulnerable users to delay upgrading indefinitely will result in more
laggards, leaving the network more exposed when quantum tech becomes available.
Steel Manning
Clearly this is a complex and controversial topic, thus it's worth thinking through the opposing
arguments.
Protecting Property Rights
Allowing quantum computers to take vulnerable bitcoin could potentially be spun as a hard money
narrative - we care so greatly about not violating someone's access to their coins that we allow
them to be stolen!
But I think the flip side to the property rights narrative is that burning vulnerable coins prevents
said property from falling into undeserving hands. If the entire Bitcoin ecosystem just stands
around and allows quantum adversaries to claim funds that rightfully belong to other users, is that
really a "win" in the "protecting property rights" category? It feels more like apathy to me.
As such, I think the "protecting property rights" argument is a wash.
Quantum Computers Won't Attack Bitcoin
There is a great deal of skepticism that sufficiently powerful quantum computers will ever exist, so
we shouldn't bother preparing for a non-existent threat. Others have argued that even if such a
computer was built, a quantum attacker would not go after bitcoin because they wouldn't want to
reveal their hand by doing so, and would instead attack other infrastructure.
It's quite difficult to quantify exactly how valuable attacking other infrastructure would be. It
also really depends upon when an entity gains quantum supremacy and thus if by that time most of the
world's systems have already been upgraded. While I think you could argue that certain entities
gaining quantum capability might not attack Bitcoin, it would only delay the inevitable - eventually
somebody will achieve the capability who decides to use it for such an attack.
Quantum Attackers Would Only Steal Small Amounts
Some have argued that even if a quantum attacker targeted bitcoin, they'd only go after old, likely
lost P2PK outputs so as to not arouse suspicion and cause a market panic.
I'm not so sure about that; why go after 50 BTC at a time when you could take 250,000 BTC with the
same effort as 50 BTC? This is a classic "zero day exploit" game theory in which an attacker knows
they have a limited amount of time before someone else discovers the exploit and either benefits
from it or patches it. Take, for example, the recent ByBit attack - the highest value crypto hack of
all time. Lazarus Group had compromised the Safe wallet front end JavaScript app and they could have
simply had it reassign ownership of everyone's Safe wallets as they were interacting with their
wallet. But instead they chose to only specifically target ByBit's wallet with $1.5 billion in it
because they wanted to maximize their extractable value. If Lazarus had started stealing from every
wallet, they would have been discovered quickly and the Safe web app would likely have been patched
well before any billion dollar wallets executed the malicious code.
I think the "only stealing small amounts" argument is strongest for Situation #2 described earlier,
where a quantum attacker arrives before quantum safe cryptography has been deployed across the
Bitcoin ecosystem. Because if it became clear that Bitcoin's cryptography was broken AND there was
nowhere safe for vulnerable users to migrate, the only logical option would be for everyone to
liquidate their bitcoin as quickly as possible. As such, I don't think it applies as strongly for
situations in which we have a migration path available.
The 21 Million Coin Supply Should be in Circulation
Some folks are arguing that it's important for the "circulating / spendable" supply to be as close
to 21M as possible and that having a significant portion of the supply out of circulation is somehow
undesirable.
While the "21M BTC" attribute is a strong memetic narrative, I don't think anyone has ever expected
that it would all be in circulation. It has always been understood that many coins will be lost, and
that's actually part of the game theory of owning bitcoin!
And remember, the 21M number in and of itself is not a particularly important detail - it's not even
mentioned in the whitepaper. What's important is that the supply is well known and not subject to
change.
Self-Sovereignty and Personal Responsibility
Bitcoin’s design empowers individuals to control their own wealth, free from centralized
intervention. This freedom comes with the burden of securing one's private keys. If quantum
computing can break obsolete cryptography, the fault lies with users who didn't move their funds to
quantum safe locking scripts. Expecting the network to shield users from their own negligence
undermines the principle that you, and not a third party, are accountable for your assets.
I think this is generally a fair point that "the community" doesn't owe you anything in terms of
helping you. I think that we do, however, need to consider the incentives and game theory in play
with regard to quantum safe Bitcoiners vs quantum vulnerable Bitcoiners. More on that later.
Code is Law
Bitcoin operates on transparent, immutable rules embedded in its protocol. If a quantum attacker
uses superior technology to derive private keys from public keys, they’re not "hacking" the system -
they're simply following what's mathematically permissible within the current code. Altering the
protocol to stop this introduces subjective human intervention, which clashes with the objective,
deterministic nature of blockchain.
While I tend to agree that code is law, one of the entire points of laws is that they can be amended
to improve their efficacy in reducing harm. Leaning on this point seems more like a pro-ossification
stance that it's better to do nothing and allow harm to occur rather than take action to stop an
attack that was foreseen far in advance.
Technological Evolution as a Feature, Not a Bug
It's well known that cryptography tends to weaken over time and eventually break. Quantum computing
is just the next step in this progression. Users who fail to adapt (e.g., by adopting quantum-
resistant wallets when available) are akin to those who ignored technological advancements like
multisig or hardware wallets. Allowing quantum theft incentivizes innovation and keeps Bitcoin’s
ecosystem dynamic, punishing complacency while rewarding vigilance.
Market Signals Drive Security
If quantum attackers start stealing funds, it sends a clear signal to the market: upgrade your
security or lose everything. This pressure accelerates the adoption of post-quantum cryptography and
strengthens Bitcoin long-term. Coddling vulnerable users delays this necessary evolution,
potentially leaving the network more exposed when quantum tech becomes widely accessible. Theft is a
brutal but effective teacher.
Centralized Blacklisting Power
Burning vulnerable funds requires centralized decision-making - a soft fork to invalidate certain
transactions. This sets a dangerous precedent for future interventions, eroding Bitcoin’s
decentralization. If quantum theft is blocked, what’s next - reversing exchange hacks? The system
must remain neutral, even if it means some lose out.
I think this could be a potential slippery slope if the proposal was to only burn specific
addresses. Rather, I'd expect a neutral proposal to burn all funds in locking script types that are
known to be quantum vulnerable. Thus, we could eliminate any subjectivity from the code.
Fairness in Competition
Quantum attackers aren't cheating; they're using publicly available physics and math. Anyone with
the resources and foresight can build or access quantum tech, just as anyone could mine Bitcoin in
2009 with a CPU. Early adopters took risks and reaped rewards; quantum innovators are doing the
same. Calling it “unfair” ignores that Bitcoin has never promised equality of outcome - only
equality of opportunity within its rules.
I find this argument to be a mischaracterization because we're not talking about CPUs. This is more
akin to talking about ASICs, except each ASIC costs millions if not billions of dollars. This is out
of reach from all but the wealthiest organizations.
Economic Resilience
Bitcoin has weathered thefts before (MTGOX, Bitfinex, FTX, etc) and emerged stronger. The market can
absorb quantum losses, with unaffected users continuing to hold and new entrants buying in at lower
prices. Fear of economic collapse overestimates the impact - the network’s antifragility thrives on
such challenges.
This is a big grey area because we don't know when a quantum computer will come online and we don't
know how quickly said computers would be able to steal bitcoin. If, for example, the first
generation of sufficiently powerful quantum computers were stealing less volume than the current
block reward then of course it will have minimal economic impact. But if they're taking thousands of
BTC per day and bringing them back into circulation, there will likely be a noticeable market impact
as it absorbs the new supply.
This is where the circumstances will really matter. If a quantum attacker appears AFTER the Bitcoin
protocol has been upgraded to support quantum resistant cryptography then we should expect the most
valuable active wallets will have upgraded and the juiciest target would be the 31,000 BTC in the
address 12ib7dApVFvg82TXKycWBNpN8kFyiAN1dr which has been dormant since 2010. In general I'd expect
that the amount of BTC re-entering the circulating supply would look somewhat similar to the mining
emission curve: volume would start off very high as the most valuable addresses are drained and then
it would fall off as quantum computers went down the list targeting addresses with less and less BTC.
Why is economic impact a factor worth considering? Miners and businesses in general. More coins
being liquidated will push down the price, which will negatively impact miner revenue. Similarly, I
can attest from working in the industry for a decade, that lower prices result in less demand from
businesses across the entire industry. As such, burning quantum vulnerable bitcoin is good for the
entire industry.
Practicality & Neutrality of Non-Intervention
There’s no reliable way to distinguish “theft” from legitimate "white hat" key recovery. If someone
loses their private key and a quantum computer recovers it, is that stealing or reclaiming? Policing
quantum actions requires invasive assumptions about intent, which Bitcoin’s trustless design can’t
accommodate. Letting the chips fall where they may avoids this mess.
Philosophical Purity
Bitcoin rejects bailouts. It’s a cold, hard system where outcomes reflect preparation and skill, not
sentimentality. If quantum computing upends the game, that’s the point - Bitcoin isn’t meant to be
safe or fair in a nanny-state sense; it’s meant to be free. Users who lose funds to quantum attacks
are casualties of liberty and their own ignorance, not victims of injustice.
Bitcoin's DAO Moment
This situation has some similarities to The DAO hack of an Ethereum smart contract in 2016, which
resulted in a fork to stop the attacker and return funds to their original owners. The game theory
is similar because it's a situation where a threat is known but there's some period of time before
the attacker can actually execute the theft. As such, there's time to mitigate the attack by
changing the protocol.
It also created a schism in the community around the true meaning of "code is law," resulting in
Ethereum Classic, which decided to allow the attacker to retain control of the stolen funds.
A soft fork to burn vulnerable bitcoin could certainly result in a hard fork if there are enough
miners who reject the soft fork and continue including transactions.
Incentives Matter
We can wax philosophical until the cows come home, but what are the actual incentives for existing
Bitcoin holders regarding this decision?
"Lost coins only make everyone else's coins worth slightly more. Think of
it as a donation to
everyone." - Satoshi Nakamoto
If true, the corollary is:
"Quantum recovered coins only make everyone else's coins worth less. Think
of it as a theft from
everyone." - Jameson Lopp
Thus, assuming we get to a point where quantum resistant signatures are supported within the Bitcoin
protocol, what's the incentive to let vulnerable coins remain spendable?
* It's not good for the actual owners of those coins. It disincentivizes owners from upgrading until
perhaps it's too late.
* It's not good for the more attentive / responsible owners of coins who have quantum secured their
stash. Allowing the circulating supply to balloon will assuredly reduce the purchasing power of all
bitcoin holders.
Forking Game Theory
From a game theory point of view, I see this as incentivizing users to upgrade their wallets. If
you disagree with the burning of vulnerable coins, all you have to do is move your funds to a
quantum safe signature scheme. Point being, I don't see there being an economic majority (or even
more than a tiny minority) of users who would fight such a soft fork. Why expend significant
resources fighting a fork when you can just move your coins to a new address?
Remember that blocking spending of certain classes of locking scripts is a tightening of the rules -
a soft fork. As such, it can be meaningfully enacted and enforced by a mere majority of hashpower.
If miners generally agree that it's in their best interest to burn vulnerable coins, are other users
going to care enough to put in the effort to run new node software that resists the soft fork? Seems
unlikely to me.
How to Execute Burning
In order to be as objective as possible, the goal would be to announce to the world that after a
specific block height / timestamp, Bitcoin nodes will no longer accept transactions (or blocks
containing such transactions) that spend funds from any scripts other than the newly instituted
quantum safe schemes.
It could take a staggered approach to first freeze funds that are susceptible to long-range attacks
such as those in P2PK scripts or those that exposed their public keys due to previously re-using
addresses, but I expect the additional complexity would drive further controversy.
How long should the grace period be in order to give the ecosystem time to upgrade? I'd say a
minimum of 1 year for software wallets to upgrade. We can only hope that hardware wallet
manufacturers are able to implement post quantum cryptography on their existing hardware with only a
firmware update.
Beyond that, it will take at least 6 months worth of block space for all users to migrate their
funds, even in a best case scenario. Though if you exclude dust UTXOs you could probably get 95% of
BTC value migrated in 1 month. Of course this is a highly optimistic situation where everyone is
completely focused on migrations - in reality it will take far longer.
Regardless, I'd think that in order to reasonably uphold Bitcoin's conservatism it would be
preferable to allow a 4 year migration window. In the meantime, mining pools could coordinate
emergency soft forking logic such that if quantum attackers materialized, they could accelerate the
countdown to the quantum vulnerable funds burn.
Random Tangential Benefits
On the plus side, burning all quantum vulnerable bitcoin would allow us to prune all of those UTXOs
out of the UTXO set, which would also clean up a lot of dust. Dust UTXOs are a bit of an annoyance
and there has even been a recent proposal for how to incentivize cleaning them up.
We should also expect that incentivizing migration of the entire UTXO set will create substantial
demand for block space that will sustain a fee market for a fairly lengthy amount of time.
In Summary
While the moral quandary of violating any of Bitcoin's inviolable properties can make this a very
complex issue to discuss, the game theory and incentives between burning vulnerable coins versus
allowing them to be claimed by entities with quantum supremacy appears to be a much simpler issue.
I, for one, am not interested in rewarding quantum capable entities by inflating the circulating
money supply just because some people lost their keys long ago and some laggards are not upgrading
their bitcoin wallet's security.
We can hope that this scenario never comes to pass, but hope is not a strategy.
I welcome your feedback upon any of the above points, and contribution of any arguments I failed to
consider.
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