Quantum computing and Bitcoin security are becoming an increasingly serious topic of discussion as investments continue to flow and certain companies like IBM, Google, and Microsoft—despite growing skepticism among serious researchers about recent high-profile projects such as Google’s Willow and especially Microsoft’s Majorana 1—are showing some progress. In any case, classical computers were also extremely bulky and underpowered at the dawn of their existence. Today, an entry-level smartphone outperforms them by far—let alone flagship devices.
This raises valid concerns about the resilience of even the most advanced encryption algorithms, especially considering that they secure private and government communications and hold massive capital stored in Bitcoin and other cryptocurrencies. While it’s impossible to define the exact timeline for quantum impact on Bitcoin, it is already worth exploring: how quantum computing affects Bitcoin, is Bitcoin secure from quantum hacks, and is there even a quantum threat to blockchain encryption?
Quantum Computing and Bitcoin Security
Before diving deeper, let’s briefly cover the fundamentals of what quantum computing actually is. Of course, fully grasping all its aspects requires a deep understanding of the math and physics behind it. However, we’ll focus on the key concepts necessary to understand the core of the issue.
Quantum computers are computational devices that approach the logic of computation from a fundamentally different perspective. Classical computers rely on transistors that either allow or block the flow of electrons. Using vast networks of these transistors, they implement binary logic, reducing all information to bits — either “0” or “1.” Quantum computers, on the other hand, operate on an entirely different level. They use different classes of materials and manipulate subatomic particles such as quanta instead of electrons, relying on distinctly quantum phenomena like superposition and entanglement.
To dive deeper into the hardware of quantum computers would require a thorough understanding of quantum mechanics — which would be excessive for now. What matters here is what this enables: quantum computers process information using qubits, which, thanks to superposition and entanglement, can exist in multiple states simultaneously — essentially between “0” and “1.” This allows for non-binary logic and enables parallel data processing on an exponential scale rather than sequentially, as in classical computing. As a result, it opens the door to solving problems that are practically unsolvable even for the most powerful classical supercomputers within any reasonable timeframe.
To put it simply, if you were to take all currently existing supercomputers and combine their power to solve a certain class of problems, it could take millions—or in some cases even billions—of years. We’re talking about literally astronomical numbers, sometimes exceeding the age of the universe or the estimated number of atoms within it.
While not every case is that dramatically large, most of the mathematical problems that form the foundation of the encryption algorithms securing the entire internet fall into this category of requiring an unreasonable amount of time to compute. Classical cryptography, in particular, relies on mathematical problems such as large number factorization (RSA), the discrete logarithm problem (DSA, DH, ECDSA), and finding hash collisions (SHA-1, SHA-2). These are considered “one-way” problems—easy to compute in one direction but extremely difficult to reverse.
Those familiar with the technical underpinnings of blockchain and cryptocurrencies in general—and Bitcoin in particular—already know where this is going. The security architecture of Bitcoin is built on two key cryptographic mechanisms – SHA-256, which ensures data integrity, and the ECDSA (Elliptic Curve Digital Signature Algorithm), which handles authentication.
SHA-256 and Quantum Computing Risks
SHA-256 is a cryptographic hash function from the SHA-2 family, developed by the U.S. National Institute of Standards and Technology (NIST), which primary purpose is to generate a unique and deterministic 256-bit hash from any input message. In Bitcoin, SHA-256 is used in two key areas: (1) to construct the blockchain itself—each block contains the hash of the previous block, ensuring data immutability; and (2) in the Proof-of-Work mechanism, where miners iterate over nonce values to find a hash that meets the target difficulty. The use of SHA-256 makes it infeasible to reverse-engineer the original message or find collisions under classical computing assumptions.
ECDSA and Quantum Computing Risks
ECDSA is based on the computational difficulty of the elliptic curve discrete logarithm problem and is used to create and verify digital signatures in transactions. When a transaction is created, the owner of the funds uses their private key to generate a signature, which can then be verified by any network participant using the corresponding public key. The security of ECDSA in the classical world rests on the fact that deriving a private key from its public counterpart requires exponential time.
Together, those two algorithms provide the functional consistency, decentralization, and resistance to known attack vectors that make Bitcoin robust in classic computation models. But can quantum computing break Bitcoin?
Is There Any Quantum Threat to Blockchain Encryption?
Both of these algorithms, however, were designed without considering the quantum computing model, and the emergence of quantum algorithms such as Grover’s Algorithm and Shor’s Algorithm significantly alters the landscape—at least potentially.
Grover’s Algorithm applies to hash functions. It allows searching an unstructured database with quadratic speedup compared to classical brute-force search. In other words, if a classical computer needs 2^n operations to search an n-bit space, a quantum computer would only need 2^(n/2). In the context of SHA-256, this means a theoretical reduction of hash strength from 256 bits to 128 bits—still secure, but with a smaller security margin. So, is Bitcoin secure from quantum hacks? Not at all, and while SHA-256 and quantum computing risks show relative resilience even in the presence of quantum attacks (due to the limited speedup of Grover’s Algorithm), the situation is more concerning with Shor’s Algorithm.
Shor’s Algorithm enables the efficient computation of discrete logarithms and the factorization of large numbers in polynomial time, making it possible to break private keys used in Bitcoin and other cryptocurrencies—provided a sufficiently powerful quantum computer exists. As a result, the security of ECDSA collapses rapidly in the presence of Shor’s Algorithm, making private keys potentially recoverable once the corresponding public key is published to the blockchain.
How Quantum Computing Affects Bitcoin?
Bitcoin vulnerability to quantum attacks is not just about breaking its core algorithms SHA-256 hash function, and especially the ECDSA signature algorithm.
For instance, it enables attack scenarios where malicious actors could exploit a fundamental aspect of Bitcoin’s transaction design: the public key is only revealed on-chain at the moment funds are being spent. This means that unspent transaction outputs (UTXOs), where the public key has not yet been disclosed, remain protected even from quantum analysis, while all addresses from which funds have already been moved are potentially vulnerable to attack. In such a case, the primary targets would be well-known addresses, such as those of major crypto exchanges or addresses linked to Satoshi Nakamoto, whose public keys have already been exposed.
It introduces broader risks, such as the potential destabilization of the entire trust architecture behind the world’s leading crypto asset, and many systems backed by Bitcoin could collapse as well. Moreover, even technically independent and quantum-resistant cryptocurrencies and blockchains may face collateral damage in a broader crypto industry decline.
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What Is the Timeline for Quantum Impact on Bitcoin?
It is difficult to say how soon we should expect a practical and direct quantum threat to Bitcoin specifically and main cryptocurrencies more broadly. The main challenge lies in the uncertainty surrounding the progress of quantum computer development, the design characteristics and implementation approaches used by different manufacturers, and the methods for measuring and describing existing quantum systems. As of 2025, the largest systems range from 100 to 1,000 qubits, but most of them raise questions about the accuracy of qubit performance evaluations. Moreover, quantum computations themselves remain unstable and error-prone, making them unsuitable for running Shor’s Algorithm at parameters applicable to ECDSA, for instance.
However, if we look at the average estimates on which most researchers agree, breaking a 256-bit key using Shor’s Algorithm would require a quantum computer with 2,330–4,000 stable qubits and millions of fault-tolerant logical operations with error correction. These estimates point to an approximate time frame of 15–30 years before such capability becomes feasible, though one should account for the possibility of exponential growth in quantum technology development—especially if driven by targeted national quantum computing initiatives.
That said, this may not even be the most critical concern because the threat of retrospective attacks cannot be ruled out: even if a capable quantum computer appears 50 years from now – all public data, keys, and transactions stored today on public blockchains could eventually be used to reconstruct private keys.
In general, Bitcoin vs quantum computers is not an abstract idea but a mathematically proven possibility. Even if the technological realization of quantum computers remains limited today, the foundation of cryptographic security has already been weakened on a theoretical level. This means that systems failing to adapt to the post-quantum reality risk being compromised in the future—particularly in cases where public keys are already exposed on the blockchain.
Post-Quantum Cryptography and Bitcoin
This recognition of classical cryptographic systems’ vulnerability to quantum attacks has already triggered a global response from the research and engineering communities. A key role is played by the NIST Post-Quantum Cryptography Standardization initiative, launched in 2016, which became the largest open evaluation process in history for cryptographic algorithms resilient to quantum attacks. PQC, in its effort to identify candidates capable of replacing vulnerable components of modern protocols—namely signatures and encryption—currently highlights CRYSTALS-Kyber (for encryption) and CRYSTALS-Dilithium, FALCON, and SPHINCS+ (for signatures). These candidates have successfully undergone years of evaluation against a range of attack vectors, including side-channel and algebraic reduction attacks.
CRYSTALS-Dilithium and FALCON hold particular relevance for Bitcoin as digital signature algorithms based on lattice-based cryptography. These algorithms were designed from the start to resist Shor’s Algorithm and demonstrate high performance in signature generation and verification, making them potential candidates to replace ECDSA in cryptocurrencies.
Other research directions include code-based, hash-based, and multivariate polynomial schemes, among which hash-based signatures—such as SPHINCS+—are considered especially resistant to quantum attacks. However, this solution is not without drawbacks, as the large size of keys and signatures may increase hardware requirements and demand more memory and computing resources.
Overall, integrating post-quantum cryptography into Bitcoin involves a range of specific challenges—from the need to modify the Bitcoin Core protocol, which requires broad community approval and developer consensus, to joint coordination among thousands of network participants. It also includes questions about validating the algorithms not only for quantum resistance but also for security against classical attacks while ensuring they are efficient enough not to increase block size or critically impact network performance and transaction costs.
Future of Bitcoin in a Quantum World and Quantum-Proof Blockchain Solutions
Thus, despite active scientific progress in PQC, Bitcoin as a protocol remains conservative and highly resistant to change, in line with its philosophy and corresponding architecture: any change requires maximum consensus, extensive auditing, and deep backward compatibility. However, in the face of the looming quantum threat, the question arises—can migration to a quantum-secure model be achieved under such constraints? And how exactly preparing Bitcoin for quantum resistance could be implemented both technically and organizationally? At this stage, we have a few most expected approaches:
- Introducing quantum-secure signatures as an optional mechanism—via a soft fork, it is possible to add new address types that use, for example, Dilithium or SPHINCS+ instead of ECDSA. Users would be able to move funds to these addresses voluntarily, ensuring future resilience without requiring immediate mandatory migration.
- Hybrid signature schemes—another option where transactions are signed using both classical and post-quantum algorithms. This would preserve backward compatibility while adding an extra layer of security.
- A hard fork with full cryptographic replacement—the most radical scenario, which would require splitting from the current chain and launching a new version of Bitcoin. This is an extremely undesirable and disruptive measure, and most experts lean toward a gradual evolutionary migration.
Quantum Resistant Ledger and Others “Quantum-Resistant” Solutions
When discussing other quantum-resistant cryptocurrencies, one must proceed with great caution, as this space is rife with speculation. In a positive sense, the first project worth mentioning is the QRL (Quantum Resistant Ledger) project — the first blockchain purpose-built from the ground up in accordance with PQC standards. It is based on XMSS (eXtended Merkle Signature Scheme), a hash-based digital signature scheme approved by NIST as part of post-quantum cryptography. XMSS incorporates Winternitz One-Time Signatures (W-OTS+), a hardened variant of the original W-OTS scheme that adds randomized hashing for improved collision resistance. XMSS further enhances security through Merkle trees, state management, and strict enforcement of one-time key usage, enabling QRL to implement a unique approach to addresses and key management, minimizing the risk of private key exposure even over long periods of time. While the project is far from Bitcoin’s scale, it serves as an important example of how a quantum-proof blockchain can be built from the ground up.
Other so-called “quantum-resistant” cryptocurrencies are far less definitive. For example, the relatively well-known Mochimo project claims to use WOTS+ (a modified version of Winternitz) and its own quantum-resistant message protocol called M-Lattice, which is based on lattice-based encryption. However, there has been no official, independent cryptographic evaluation of these implementations, and the codebase and protocols have not undergone public scrutiny comparable to that of NIST PQC candidates.
Some efforts by even more prominent cryptocurrencies appear even more contentious, and IOTA, for example, with each of its high-profile efforts in this direction, tends to amplify rather than resolve the uncertainty surrounding its approach. Until 2021, IOTA did indeed use the original W-OTS scheme, which lacked collision resistance and protections against key reuse. In April 2021, the project transitioned to a new version called Chrysalis (IOTA 1.5), where it abandoned Winternitz in favor of Ed25519—a widely used implementation of EdDSA based on elliptic curves. However, Ed25519 is vulnerable to Shor’s Algorithm and requires fewer qubits to break than, for example, RSA. Despite this, IOTA states that it can quickly switch to a quantum-secure signature scheme once a reliable standard—such as one of the NIST PQC finalists—is available.
When it comes to quantum computers and crypto wallets, there are no fundamental differences, and this area, too, is surrounded by speculation. Crypto wallets, especially hot wallets, are subject to the same risks posed by quantum algorithms, and there is currently no clearly promising solution available. In general terms, there are secure hot wallets and even more secure cold wallets, but any wallet whose public key has already been recorded on the blockchain is vulnerable—regardless of whether it is cold or hot.
Conclusion
Admittedly, this all sounds quite alarming—but not hopeless. It’s worth noting that we’ve been hearing about the coming breakthroughs in quantum computing for decades. Of course, that doesn’t negate the associated risks. As of today, those risks are well modeled, and their potential impact grows in proportion to the rapid digitization and tokenization of assets—especially in recent years. Still, tangible and sustained breakthroughs in quantum computing remain abstract for now, giving us a window of opportunity to prepare for this possible future, whether it arrives sooner or later.
Key institutions—backed by some of the best mathematicians, cryptographers, and engineers—already have promising foundations in place, and research is ongoing. Meanwhile, some blockchain and cryptocurrency projects are not merely adapting to this challenge but are being designed from scratch to comply with post-quantum standards.
We already see this in the emerging synergy between blockchain and AI — where entirely new coalitions are being formed to enhance each other’s capabilities, such as AI Unbundled or the Artificial Superintelligence Alliance. The latter is even building its own stack from the ground up, as in the case of Fetch.ai with their LLM ASI-1 Mini.In any case, we are clearly living through a pivotal moment in history. First came DeFi, slowly but steadily reshaping the established order. Then came AI, despite its early stages, has begun to upend the rules entirely. And if quantum computers are indeed on the horizon, it is most certainly time to prepare.
