# Post-Quantum Readiness: Is Your Blockchain Actually Secure?

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Almost every blockchain today is quantum vulnerable. Dr. Joseph Kearney and the QRL team break down the spectrum of post-quantum readiness, ranging from vulnerable to fully post-quantum native, and explain what it takes for a blockchain to be truly secure. 

Published: 2026-07-31
Updated: 2026-07-31



Author: The QRL Core Contributors



Categories: technical












Over the past year or two, it has become almost impossible to browse crypto Twitter without running into the phrase “post-quantum.” Projects are adding it to roadmaps, announcements, and marketing copy, but there are no shared standards for what the term actually means or when a project has earned the right to use it. The result is widespread confusion among users who hear “post-quantum” and assume the box has been checked.
In this episode of the QRL show, recorded in Singapore, the hosts sat down with Dr. Joseph Kearney, a post-quantum cryptography expert and technical advisor to the QRL, to break down the constraints projects face when migrating to post-quantum cryptography. The conversation centers on a spectrum of classifications: post-quantum vulnerable, post-quantum enabled, post-quantum resistant, and post-quantum native, a chain designed with the quantum threat in mind from the very beginning.
Almost Every Blockchain Project Out There Today is Quantum Vulnerable The Majority of Blockchains Today are Post-Quantum Vulnerable Why a Plan Doesn’t Equal a Solution The Many Decisions and Caveats of Transitioning How Should Individuals Be Evaluating Projects in Regards to Post-Quantum Readiness? How Confident Are Cryptographers Building on Vulnerable Blockchains in Their Ability to Transition? The Industry Continues to Take the Quantum Threat More Seriously What Projects Are Post-Quantum Native? QRL, Post-Quantum Native Since Day 1 Why Build/Run on QRL 2.0 When It Hits Mainnet? Conclusion Almost Every Blockchain Project Out There Today is Quantum Vulnerable Over the past 12 to 18 months, nearly every blockchain project has started attaching the words “post-quantum” to their messaging. But there are no real standards for how those words are used, what they reference, or what they actually mean. This has created significant confusion across social media and within the broader crypto community.
The goal of this discussion is to bring clarity, and to break down the classifications of blockchain post-quantum readiness into a few categories: post-quantum vulnerable, post-quantum enabled, post-quantum resistant, and post-quantum native. Understanding where a project falls on this spectrum is essential for anyone who holds digital assets or builds on a blockchain.
The Majority of Blockchains Today are Post-Quantum Vulnerable The stark reality is that almost every blockchain currently in deployment is post-quantum vulnerable. The reason is straightforward: nearly all of them rely in some way on ECDSA or EdDSA, forms of elliptic curve cryptography, for their security. Shor’s algorithm, running on a sufficiently powerful quantum computer, will eventually be able to break these, which means it could be used to hijack cryptocurrency.
This is a massive concern. The amount of data already exposed, public keys, authority keys for smart contracts, and more, means that upgrading every account, smart contract, and component within the blockchain ecosystem to post-quantum cryptography will require a monumental effort.
We’re not just talking about layer-1 blockchains. Layer-2 tokens, ERC-20 tokens, NFTs, and real-world assets tied to ownership on chain are all reliant on the base cryptography of their underlying chain. When you factor in the physical value of real-world assets stored on chain, the stakes extend well beyond the roughly $2 trillion cryptocurrency market cap. And given how intertwined blockchain has become with traditional finance, the ripple effects of a quantum attack would be enormous.
Why a Plan Doesn’t Equal a Solution Many users have seen their favorite project announce a post-quantum strategy and concluded there’s nothing left to worry about. The problem is that if the underlying cryptography of a chain is vulnerable, bolting post-quantum features on top doesn’t make the chain post-quantum native.
When Bitcoin launched, quantum computing wasn’t even a topic of conversation. The asymmetric cryptography that Bitcoin and many subsequent projects adopted has been around since the late 1970s and was further developed through the 1980s. At the time, ECDSA was the perfect choice for cryptocurrency: it verified fast, signed fast, and produced small public keys and signatures. Shor’s algorithm was a theoretical mathematical argument against something that seemed unlikely to materialize.
But now projects face a complex problem that has to be essentially bolted onto existing infrastructure. And because these projects operate through decentralized communities of global developers, reaching consensus on how to solve the problem is itself a challenge. Participants may have different philosophies, agendas, values, and interpretations of what a project’s ethos means, including what property ownership actually signifies and whether losses could or should be compensated.
The Many Decisions and Caveats of Transitioning Transitioning a blockchain to post-quantum security requires a series of difficult decisions. First, which digital signature scheme do you adopt? That decision has to be lived with for a long time. Then there’s the question of how to upgrade: do you use a clever zero-knowledge proof system, a registry system as in Ethereum’s case, or some kind of account abstraction? Each option is as contentious as the last.
And every solution comes with caveats. For example, some zero-knowledge migration approaches rely on proving knowledge of a root seed from which an account’s signing key was deterministically derived. There is no pure approach that solves the problem without making compromises, whether that’s selecting winners and losers, compromising on philosophy, or accepting some other trade-off.
One analysis of Bitcoin’s potential migration path estimated that if every user sent a transaction to upgrade their signature, the minimum time would be 76 days of downtime using 100% of block space, and that assumed unrealistic conditions. In reality, the process would more likely take three to four years. You’d have to interlace migration transactions with regular network activity to keep the chain running. Then comes the hardest question: what do you do with anyone who can’t or doesn’t upgrade? Post-quantum signatures also tend to be larger, which means they take up more block space. Do you accept a drop in transactions per second, or debate yet another block size increase?
Each of these individual questions has the potential for months, if not years, of debate.
How Should Individuals Be Evaluating Projects in Regards to Post-Quantum Readiness? For individuals,whether retail investors or high networth participants, evaluating a project’s post-quantum claims requires critical thinking. When a project announces a post-quantum strategy, it’s worth asking: is this signal or noise?
A useful framework is understanding the distinction between post-quantum enabled and post-quantum resistant. A project that is post-quantum enabled gives users the option to secure themselves using post-quantum cryptography within its ecosystem. That’s an admirable and important step, it’s better to give users that ability than to keep it theoretical. But being post-quantum enabled does not make the whole chain post-quantum resistant. The critical question is: if a cryptographically relevant quantum computer (CRQC) came online tomorrow, would that chain be secure or even survive?
There aren’t many blockchains that weren’t originally quantum native that could answer that question with confidence. Individuals should look past marketing language and examine whether a project has taken meaningful steps toward actual chain-wide resistance, or whether it has simply added a feature that lets some users opt into post-quantum security.
How Confident Are Cryptographers Building on Vulnerable Blockchains in Their Ability to Transition? Asked whether developers of post-quantum enabled chains might be operating under a false sense of confidence, Kearney is unequivocal: no.
The cryptographers working on these transition problems are some of the best in the world. They understand blockchain and cryptography deeply, and they’ve come up with creative solutions, like zero-knowledge proofs, that demonstrate real ingenuity. Giving users the ability to secure themselves post-quantumly is a critical first step and shouldn’t be dismissed.
At the same time, these are extremely smart people trying to solve what is essentially an impossible problem to solve cleanly. There is no pure approach that doesn’t involve compromise. When projects present a confident narrative about their post-quantum progress, there’s likely some internal tension, what they’re being asked to say, or feel compelled to say, given what’s at stake, may not fully align with the complexity of what’s been coded. Trust is the one thing you can’t compromise in a cryptocurrency system. You trust the code, and you trust the cryptography. If the cryptography isn’t secure, trust in the entire system falls apart.
Kearney closes the section with an observation that follows naturally: the projects that started working on this earliest tend to be the ones that already had more sophisticated cryptography. Those teams already understood a great deal of the relevant math, so their head start isn’t surprising.
The Industry Continues to Take the Quantum Threat More Seriously The tide has shifted. Over the past year in particular, projects, individuals inside the industry, and observers outside it have all begun treating the quantum threat more seriously. The pattern echoes what happened with AI, where projects rushed to attach two letters to their branding, now the phrase being attached is “post-quantum.”
A large bucket of projects still sits firmly in the vulnerable category, and quantum computing progress at major companies continues regardless of what happens at the blockchain project level. That means urgency will keep building.
Using Bitcoin as the example, Kearney lays out how he thinks a transition would have to proceed. He’s careful to note he isn’t a Bitcoin Core developer and isn’t making these decisions.
Step one is giving users the ability to use post-quantum cryptography. Whether they actually use it is a separate matter; having the choice is what counts. Once a post-quantum signature scheme exists on the chain, the discussion can begin.
His downtime paper assumed the primary upgrade mechanism would simply be users sending transactions, an ECDSA signature on one side, a post-quantum signature such as ML-DSA, FN-DSA, or SLH-DSA on the other, and the user emerges post-quantum secure. Under that model, the theoretical minimum was roughly 76 days of downtime, but that figure assumed 100% of block capacity was devoted to migration, an assumption he describes as ridiculous in practice. Given how slowly people actually act, the realistic timeframe is more like three to four years. That raises the question of whether there’s a block height at which the migration window closes, or whether there isn’t one at all. It also means migration transactions would have to be interlaced with normal network traffic to keep the chain running.
Step two is the possibility that Bitcoin introduces a clever zero-knowledge proof system to facilitate the upgrade.
Step three is the hardest: what do you do with anyone who can’t upgrade? Contained within that question is another, whether additional protocol changes are needed at all. The available post-quantum options, whether standardized (ML-DSA, FN-DSA, SLH-DSA, XMSS) or still emerging, generally have larger signatures and larger public keys. That consumes block space. Do you accept a drop in transactions per second, or not? Kearney has no desire to make an old-school Bitcoin developer shudder at the thought of another block size debate, but the trade-off is real: post-quantum cryptography does not bring efficiency gains.
Each of these individual questions carries the potential for months or years of debate, and each one opens up a fresh set of questions. It all illustrates the same point: if a chain doesn’t start post-quantum native, moving toward post-quantum security will naturally come with caveats.
What Projects Are Post-Quantum Native? A post-quantum native blockchain can be defined simply: a post-quantum native blockchain is one that has no known quantum computing attack vectors, and, going further, has never had any. That requires a post-quantum signature scheme from genesis and a project built from the ground up with post-quantum security in mind.
The number of projects meeting this standard can be counted on one hand. One notable recent example is Circle’s ARC, which announced it will be post-quantum from genesis. That a major company is taking the threat this seriously reflects how the industry’s posture has evolved, from dismissing the quantum threat as decades away to actively designing around it.
Still, the number of projects that can claim quantum security since genesis on an L1 can be counted on one hand. Solidity developers deciding where to deploy a DeFi application or NFT project are making a long-term bet. The analogy is, you don’t want to buy a house in a neighborhood you later discover is a flood zone. You want to build somewhere with longevity.
QRL, Post-Quantum Native Since Day 1 The Quantum Resistant Ledger (QRL) has been post-quantum secure since its genesis in 2018, using XMSS, a NIST-recommended, hash-based signature scheme. When the digital signature algorithm was selected for QRL, there were over 70 NIST submissions from finalists vying to become the government-recommended post-quantum standard. The practical benefit, is peace of mind, you don’t have to worry about the quantum threat at all.
What sets QRL apart is consistency. The core message has remained the same for over five years: the threat from a sufficiently powerful quantum computer is real, the attack vectors are well understood, and the solution is to build with post-quantum cryptography from the start. The story hasn’t changed to fit a shifting narrative.
For those deciding where to build, that kind of long-term consistency matters. The question worth asking of any project is: who looked into the future, got it right, and hasn’t changed their story?
Strike frames the project’s posture carefully. Many on the team have been in blockchain for a very long time, and the goal isn’t to spread fear, uncertainty, and doubt. The QRL positions itself as an effort to help preserve the ecosystem. The conversations have grown more productive over time. At conferences, the reaction used to be that the quantum threat was FUD, something 20 or 30 years out; now there’s genuine acknowledgment. As Strike points out, if you truly believe it’s decades away, it’s worth asking why you’d be worried about what the QRL is doing at all.
Why Build/Run on QRL 2.0 When It Hits Mainnet? QRL 2.0, currently undergoing two independent third-party security audits, will bring EVM friendliness to a post-quantum native blockchain. This means existing projects running on Ethereum can take their source code, recompile it, and run it on QRL 2.0 for little to no cost.
The barrier to entry will be low enough that most projects should be able to operate across multiple chains. Being able to tell your users that you have a purist, post-quantum secure solution in mind for your project brings confidence and trust, and trust is at the center of everything in this space.
Conclusion Kearney’s closing advice is straightforward: think critically and do your own research. That’s simultaneously the key and the hardest part, because it takes time, but the investment makes a real difference. When you next encounter a project attaching “post-quantum” to its name, you now have enough context to place it somewhere on the spectrum. From there, dig further, according to whether you’re a developer deep in the weeds, an investor, or simply curious. More research never hurts.
Transitioning is an inherently difficult, multi-year process filled with compromises and contentious decisions. Post-quantum enabled is a meaningful step, but it isn’t the same as being resistant or native. The best thing individuals can do is think critically and do their own research. When a project claims post-quantum readiness, dig into what that actually means. Understand the classifications. Ask whether the chain as a whole would survive if a cryptographically relevant quantum computer came online tomorrow.
For developers, the message is equally clear: if you’re starting a new token, DeFi project, or any on-chain initiative, you should be building on post-quantum native technology. The tools to do so exist today, and the cost of waiting is only going to grow.