The idea of a quantum computer that could break the security of a cryptocurrency wallet in a short time and access its contents may sound like sci-fi. However, the development of quantum computers is progressing so rapidly that technology companies, governments, and blockchain networks themselves are beginning to prepare for such a scenario. Ethereum has now set a specific deadline – by the end of 2029, it wants its basic infrastructure to be ready for a world where current cryptographic security may no longer be sufficient.
Table of Contents:
- Ethereum Sets a Deadline: December 2029
- Why Are Cryptocurrencies Actually Vulnerable to Quantum Computers?
- Researchers This Year Significantly Reduced the Required Power Estimate
- What Would Happen If Someone Actually Broke Quantum Security?
- Should investors start worrying about their ETH?
- Wallets will need to get new "locks"
- The problem doesn't only concern Ethereum
- What is Q-day and why doesn't anyone know when it will come?
Ethereum Sets a Deadline: December 2029
The Ethereum Foundation published updated priorities for the network’s further development at the beginning of September. One of the most prominent commitments is the plan to achieve quantum resistance for Ethereum at the transaction, consensus, and data levels by December 2029.
This doesn’t mean that developers expect someone to turn on a quantum computer on January 1, 2030 and start emptying cryptocurrency wallets. On the contrary, the Ethereum Foundation acknowledges that most credible estimates push the so-called Q-day – the moment when quantum computers will be capable of realistically breaking currently used cryptography – further into the future.
However, the network has decided to work with a very conservative scenario and plan as if Q-day could arrive around 2030. The reason is simple – replacing the cryptographic foundations of a global blockchain network is not something that can be done in a few weeks.
Google, for example, is proceeding similarly, also setting 2029 as an important deadline for migrating systems to post-quantum cryptography.
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Why Are Cryptocurrencies Actually Vulnerable to Quantum Computers?
Cryptocurrencies are based on cryptography. Among other things, it ensures that only the person who owns the corresponding private key can handle the funds in a wallet.
In very simplified terms, the entire system can be compared to a safe. The public blockchain address indicates where the safe is located, while the private key represents the combination needed to open it.
For classical computers, the mathematical problem on which the security is based is practically insurmountable. Theoretically, it would be possible to calculate the private key, but in practice, with current computing capabilities, it would take an impractically long time.
Quantum computers work differently. For cryptography, Shor’s algorithm is particularly important, which would allow a sufficiently powerful quantum computer to solve certain mathematical problems dramatically more efficiently than today’s machines.
These problems form the basis of security for a large part of the current internet and cryptocurrencies.
Ethereum, for example, uses the ECDSA algorithm based on elliptic curve cryptography for signing transactions. It also uses other quantum-vulnerable cryptographic technologies in the operation of validators, data handling, or certain types of zero-knowledge proofs.
Researchers This Year Significantly Reduced the Required Power Estimate
The urgency of the topic was heightened by research published this spring by experts from Google Quantum AI and other institutions. They focused on the question of how powerful a quantum computer would need to be to break the 256-bit elliptic curve cryptography used by cryptocurrencies, among others.
According to research published by Google, one variant of the attack could require less than 1,200 logical qubits and approximately 90 million so-called Toffoli operations. This represents significantly lower requirements than some older estimates suggested.
However, this doesn’t mean that such an attack can be carried out today. A logical qubit is not the same as a physical qubit, which is commonly discussed when presenting current quantum computers. Quantum systems are very prone to errors, and creating a reliable logical qubit requires complex error correction and more physical hardware.
There is still a significant technological gap between today’s experimental quantum computers and a machine capable of systematically attacking cryptography.
However, the development shows why security experts don’t want to wait until such a machine actually exists.
What Would Happen If Someone Actually Broke Quantum Security?
For cryptocurrency holders, the most dangerous scenario would be the ability to derive a private key from publicly available information.
If an attacker obtained the private key to a wallet, the blockchain would practically be unable to distinguish them from its actual owner. They could create a valid transaction and transfer the funds elsewhere.
The blockchain would technically function exactly as it should. The problem wouldn’t be that someone “hacked Ethereum,” but that the mathematical assumption on which ownership verification of cryptocurrencies is based would no longer hold.
An interesting detail concerns wallets that have never sent any transaction. With standard Ethereum accounts, when sending a transaction, information is revealed that allows reconstruction of the public key. If a wallet has only received ETH and never signed any transaction, only the address derived from the public key is visible on the blockchain, which provides it with an additional layer of protection. Even so, Ethereum expects that in the future, all accounts should transition to a new security method.
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Should investors start worrying about their ETH?
Not at the moment. Ethereum explicitly states in its materials that no quantum computer today is capable of breaking Ethereum’s cryptography. Users therefore do not need to move their ETH, change their wallet, or take any other extraordinary steps right now. Much more importantly, the transition will begin before the actual threat emerges.
In January this year, Ethereum created a specialized team focused on post-quantum security. Developers are already testing new cryptographic mechanisms, and more than ten teams developing Ethereum clients participate in regular testing. The goal is not to discard current cryptography and replace it with new technology in a single upgrade. The transformation is meant to be gradual.
Wallets will need to get new “locks”
One of the most important issues is the method of signing transactions. Ethereum is therefore working with a concept that would allow individual accounts to use different signature verification methods. Practically, this would mean that users will be able to transition in the future from today’s quantum-vulnerable technology to a new post-quantum signature without the entire network having to change its system at the same moment.
Related to this is also the EIP-8141 proposal and the broader concept of native account abstraction, which Ethereum mentions among the options for further strengthening protocol security.
For the average cryptocurrency owner, the resulting change should be considerably less dramatic than its technical background suggests. Ethereum anticipates that when the transition is actually needed, cryptocurrency wallets themselves will guide users through the migration. Instead of manually studying post-quantum cryptography, the result may simply be a notification in the app and the conversion of the account to a new security standard.
The problem doesn’t only concern Ethereum
The quantum threat is certainly not a specific problem of the second-largest cryptocurrency. Elliptic curves are also used by Bitcoin, and similar cryptographic principles are used by a large portion of the digital economy. The potential emergence of a cryptographically relevant quantum computer would therefore not be a “crypto problem,” but a fundamental event for the security of the entire internet, financial institutions, government systems, and digital signatures.
This is why government institutions have also been working on new standards for several years. The U.S. National Institute of Standards and Technology (NIST) completed the first three main post-quantum cryptography standards in August 2024. These are algorithms designed to resist both conventional and future quantum computers.
The transition therefore doesn’t begin only when the first dangerous quantum machine appears. In the world of information security, it is already underway.
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What is Q-day and why doesn’t anyone know when it will come?
The term Q-day refers to a hypothetical moment when a sufficiently powerful and reliable quantum computer capable of realistically attacking currently used cryptographic systems is created. No one knows exactly when it will happen.
It could be at the beginning of the next decade, it could be considerably further away, and technological development may encounter obstacles that today’s forecasts don’t take into account.
Ethereum Foundation therefore emphasizes that 2030 is not its forecast. It’s a deliberately aggressive security assumption. The network wants to prepare as if the quantum threat could arrive precisely then, instead of relying on more optimistic estimates.
This is a fundamental difference. Ethereum is not claiming that the quantum apocalypse of cryptocurrencies will come in three years. It’s saying that if blockchain has the ambition to function for decades to come, it’s not reasonable to start solving the problem only when it becomes imminent.
