Quantum Threat to Bitcoin’s Security
Recent insights from Google’s Quantum AI team suggest that compromising Bitcoin’s blockchain using quantum computers might be easier than previously believed. Their findings, shared in a recent blog post and a new white paper, point towards Bitcoin’s Taproot technology as a potential factor in this vulnerability.
The researchers indicate that the computational resources needed to breach Bitcoin’s security could be much less than the “millions of qubits” often referenced in discussions. They estimate that fewer than 500,000 physical qubits might be sufficient to crack the encryption used by both Bitcoin and Ethereum, which certainly raises eyebrows about how soon quantum threats could materialize.
Google previously highlighted 2029 as a key year for viable quantum systems, and the revelation that these attacks might require less power than expected makes for a concerning development.
Quantum computers operate using qubits, providing the ability to tackle specific issues at a pace that surpasses traditional machines, including breaking the encryption protecting cryptocurrency wallets.
According to their research, Google has outlined two potential attack strategies, each needing around 1,200 to 1,450 high-quality qubits. This aligns with earlier predictions that suggest the gap between current technology and possible attacks might be narrower than investors generally perceive.
The research also explains the practicalities of such attacks. Instead of targeting older, dormant wallets, quantum hackers could monitor transactions as they occur. When Bitcoin is sent, a public key is temporarily exposed. A fast enough quantum computer could compute the corresponding private key, enabling the theft of funds.
In their scenario, a quantum system could set up calculations in advance and launch an attack in approximately nine minutes from the time a transaction is initiated—a timeframe that’s similar to Bitcoin’s average transaction confirmation time of about 10 minutes. This gives an attacker roughly a 41% chance of intercepting the transaction.
Other cryptocurrencies, like Ethereum, may face less vulnerability due to their quicker transaction confirmations and shorter attack windows.
The study also reveals that around 6.9 million Bitcoins, or roughly one-third of the total supply, are currently in wallets with exposed public keys. This includes about 1.7 million Bitcoins from the network’s early days and funds at risk due to address reuse.
The numbers starkly contrast a recent estimate from CoinShares, which suggested only about 10,200 Bitcoins would significantly impact the market if stolen.
Concerns About Taproot
The findings also provide new context for Bitcoin’s 2021 Taproot upgrade. While Taproot enhances privacy and efficiency, it makes public keys visible on the blockchain by default, which may remove a layer of protection present in older address formats.
Researchers from Google caution that these design choices might expand the universe of wallets at risk of future quantum attacks.
In response, Google is altering how it shares sensitive security research. Instead of revealing details step by step, they’re employing a method known as zero-knowledge proof. This allows them to validate their findings without disclosing the specific methods, minimizing the risk of misuse.
For investors, the key takeaway isn’t that quantum computers are just about to dismantle cryptocurrencies, but rather that the timeline for such risks might be shorter and more widespread than many previously understood.
