Quantum computing cracking 15-digit private keys? The truth is quite the opposite

BTC continues to decline slightly, reaching 77k. Whenever this happens, there’s always some news to stir the pot. This time, it’s quantum computing again.

Cointelegraph reported a piece of news: researcher Giancarlo Lelli successfully cracked a 15-bit elliptic curve key using a quantum computer, and Bitcoin uses the same type of encryption algorithm. [1] Once the news broke, the internet immediately exploded. Some exclaimed that Bitcoin would go to zero, others started promoting so-called anti-quantum coins, and some even outright claimed there’s little time left for BTC.

Seeing such news, the first reaction from the blockchain community is that there’s something fishy.

Every one or two years, quantum computing makes a splash to boost its presence. It’s always the same formula, the same familiar story. But this time, it’s a quantum computer that cracked a 15-bit key on stage. Sounds impressive, but a closer look reveals several traps.

Trap 1: 15 bits vs 256 bits

The core selling point of the report emphasizes the same type of encryption. Implying that quantum computers can already crack the algorithms used by Bitcoin.

But here’s a critical detail: the cracked key is 15 bits, while Bitcoin uses a 256-bit key. How big is this gap? Let me give you an intuitive sense.

A 15-bit key space is about 32k possibilities (haha). You can brute-force it with any laptop or even a mobile phone in less than a millisecond. It’s not a technical challenge but a task a middle schooler can do.

And how big is a 256-bit key space? It’s 2 to the 256th power. How enormous is this number? It exceeds the total number of atoms in the universe by several orders of magnitude. Even if all traditional computers on Earth tried to brute-force it from the universe’s birth to its end, they wouldn’t find the correct private key.

The report conflates cracking a 15-bit key with threatening a 256-bit one, like someone claiming to have broken the 100-meter world record, but in reality, they only ran one meter. The principle is correct—they’re both running—but the practical significance is worlds apart.

Trap 2: The hidden cost of quantum advantage

Some might argue that quantum computers don’t rely on brute-force but on the mathematical trick of Shor’s algorithm. Even if they can only crack 15 bits now, they can eventually extend to 256 bits, and the time will only grow linearly.

This is mathematically correct, but physically and engineering-wise, it ignores a fatal problem: the explosion of costs.

As previously emphasized in our articles, there’s no free lunch. Classical computers cracking encryption face exponential time costs; quantum computers cracking encryption face exponential physical resource costs. [2]

Cracking a 15-bit key might require dozens of physical qubits. But cracking a 256-bit key is estimated to need millions of high-quality, low-error physical qubits. [3] Going from dozens to millions is not linear growth but a leap of four orders of magnitude.

Even more daunting, qubits are extremely fragile, requiring ultra-low temperatures, complex error correction, and near-perfect control. Each additional order of magnitude in qubits doesn’t just double the difficulty; it causes an exponential increase. Currently, the most advanced Google Willow quantum computer has only 105 physical qubits. [4] The gap from 105 to millions isn’t a matter of years but a technological chasm.

The report says nothing about this, as if going from 15 bits to 256 bits is just one step. This omission is precisely a key tactic to induce panic.

Trap 3: Bitcoin isn’t defenseless

Even if we assume, for the sake of argument, that someday quantum computers truly reach that level, Bitcoin isn’t defenseless.

Satoshi Nakamoto already considered this issue when designing Bitcoin. Bitcoin addresses store not the public key itself but the hash of the public key. Hash functions are naturally resistant to quantum attacks. Grover’s algorithm can reduce the difficulty of attacking a hash from 2^256 to 2^128, which is still astronomically large. [5]

As long as your Bitcoin is stored in a P2PKH address (starting with 1) or a P2WPKH address (starting with bc1q), and you’ve never used the address (meaning the public key has not been exposed), then a quantum computer faces only the hash layer, not the vulnerable elliptic curve signature. As Satoshi said in 2010: transactions paid to Bitcoin addresses are only as secure as the hash’s security. [6]

This is a subtle but extremely important technical detail. The report omits it because mentioning it would spoil the scare.

Trap 4: Bitcoin is alive

Finally, and most importantly: Bitcoin isn’t dead. It can be upgraded.

The threat of quantum computing isn’t a recent discovery; the Bitcoin community has been researching countermeasures for years. The Taproot upgrade activated in 2021 has already paved the way for future signature algorithm changes. [7] Research into quantum-resistant signatures is ongoing, but current solutions are not yet mature—mainly because larger signature sizes could cause Bitcoin blocks to swell by hundreds or thousands of times, contradicting Satoshi’s original choice of ECC over RSA.

When quantum computing truly approaches the threat threshold, the Bitcoin community can initiate a soft fork to replace the signature scheme with a quantum-resistant one. This process won’t be more complicated than the 2021 Taproot upgrade.

Compared to that, traditional banking systems, internet security frameworks, and military communication systems face more direct and severe quantum threats, and their upgrades are even more challenging. If quantum computers become practical one day, the first to suffer won’t be Bitcoin holders but central banks, Pentagon, and global cybersecurity engineers.

The panic behind the fear

If the logic is so clear, why do waves of quantum panic keep recurring?

Our observation suggests there are roughly three types of promoters behind this.

First are the media. Headlines about quantum computing cracking encryption naturally attract attention. Whether it’s about cracking 15-bit or 256-bit keys, whether in lab conditions or real environments, these details are too dull for headlines. Clicks are king, and the truth can come later.

Second are those exploiting panic to sell products. Every time a wave of quantum fear hits, some projects jump out to promote so-called anti-quantum coins. Our article last June warned about anti-quantum scams. [8] These projects are usually technically terrible but are hyped with grand concepts, aiming to harvest panicked retail investors. When you encounter such projects, just blacklist them—chances are they’re either stupid or malicious.

Third are ordinary investors swept up in emotion. They see the headlines and panic, without reading the details or verifying the tech. During market downturns, panic can amplify, creating a vicious cycle.

Preparedness, not paranoia

Our purpose in writing this isn’t to deny the real long-term threat of quantum computing. It’s a genuine risk we can’t ignore. But the right attitude toward risk is preparedness, not panic.

For ordinary Bitcoin holders, there are simple steps now to reduce future quantum risks:

First, check your address type. Prefer P2PKH (starting with 1) or P2WPKH (starting with bc1q) addresses, and avoid P2PK (early addresses exposing public keys directly) or P2TR (bc1p addresses that also expose public keys). [5]

Second, avoid address reuse. Use each address only once. If you need to spend from an address, transfer all funds out at once, then never reuse that address. This minimizes the window during which your public key is exposed.

Third, don’t wait until the last moment. If, in the future, many users start migrating, on-chain fees will skyrocket. It’s wise to act now, while the network is calm, and prepare in advance.

As for those who spread quantum panic daily and promote all kinds of dubious projects, remember: the quantum computer isn’t here yet, but their scythe is already visible.

Bitcoin has faced countless existential threats—from government bans to mining collapses, from 51% attacks to hard forks. Every time, someone predicted its demise, but Bitcoin always survived.

Quantum computing won’t be Bitcoin’s end. It’s just another test in its long history. And Bitcoin’s design has always been prepared for such challenges.

Rather than being swept by panic, it’s better to stay calm, understand the technology, see the logic clearly, and make rational judgments.