THE ADVENT OF QUANTUM COMPUTERS: A THREAT TO YOUR BITCOINS?

You have no doubt heard about *quantum computers*, those revolutionary machines that promise to transform our digital world.

But a recent announcement by researchers from *Google* sent shockwaves through the cryptocurrency sector: these computers could represent a far more imminent threat to cryptocurrency security than expected.

Let us explore together what this really means for your Bitcoin wallet and the future of the blockchain.

A recent study conducted by *Craig Gidney, a researcher at Google Quantum AI, revealed that quantum computers could be 20 times more efficient than expected at breaking certain cryptographic systems, notably 2048-bit RSA.*

According to his estimates, a 2048-bit RSA integer could be decrypted in less than a week by a quantum computer with fewer than one million noisy qubits, whereas previous estimates spoke of around 20 million qubits.

This breakthrough could have direct implications for cryptocurrency security, even though Bitcoin does not directly use RSA but ECDSA (Elliptic Curve Digital Signature Algorithm), another form of cryptography that could also be vulnerable to quantum attacks. (CoinDesk)

To understand the threat, one must first understand *how cryptocurrency security works.* Digital currencies like Bitcoin rely on public-key cryptography principles:

1. 1.Private and public keys: Each user has two keys. The public key is like an account number, visible to everyone. The private key is like a highly secret password, which allows you to prove that you are the owner of the account.
2. 2.Digital signatures: When you send bitcoin, you "sign" the transaction with your private key. This proves that it is indeed you, without needing to show this key to anyone. The public key allows this signature to be verified.
3. 3.Hash functions: Bitcoin uses special mathematical formulas (such as SHA-256) to secure the blockchain and the work of miners.

The security of this system relies on *mathematical problems that are extremely difficult to solve* for classical computers, such as the factorisation of large prime numbers or calculating discrete logarithms on elliptic curves.

*Quantum computers are very different from classical computers.*

They use principles that completely change the way calculations are performed:

• Quantum superposition: A classical bit is worth 0 or 1. A qubit, however, can be in multiple states at the same time, allowing far more information to be processed at once.
• Shor's algorithm: This quantum algorithm can rapidly break protections based on large prime numbers. This represents a direct threat to the security of cryptocurrencies.
• Double threat:

A recent discovery by Craig Gidney makes this threat *even more serious*: he showed that quantum computers would require far fewer resources than expected to succeed in these attacks.

*Here is a great YouTube video to help you better understand*: youtube

Despite this significant theoretical breakthrough, it is important to put things into perspective:

1. 1.Current state of quantum computers: The most powerful quantum computers available today are far from achieving the capabilities required for these attacks. IBM's Condor, considered the most powerful, reaches only 1,121 qubits, whilst Google's Sycamore operates with 53 qubits.
2. 2.Future projections: IBM plans to develop a 100,000-qubit quantum computer by 2033, in partnership with the University of Tokyo and the University of Chicago. However, we are still far from the one million qubits mentioned by Gidney.
3. 3.Difference between theory and practice: There is a substantial gap between theoretical advances and the construction of stable, functional quantum computers at scale.

In the face of this threat, several solutions are actively being developed:

1. 1.Post-quantum cryptography: New forms of cryptography resistant to quantum attacks are under development. NIST (the US National Institute of Standards and Technology) has already selected several promising algorithms.
2. 2.Address migration: A recent proposal called the "Quantum-Resistant Address Migration Protocol" suggests migrating funds from old, vulnerable addresses to new quantum-resistant addresses via a Bitcoin hard fork.
3. 3.Migration deadlines: This proposal would include a deadline after which transactions originating from old addresses would become invalid, thereby forcing users to migrate their funds.
4. 4.Natively resistant blockchains: Certain cryptocurrencies, such as Quantum Resistant Ledger (QRL), were designed from the outset to resist quantum attacks.

The transition to a quantum-resistant Bitcoin is not without its challenges:

1. 1.Community consensus: Any major modification to the Bitcoin protocol requires a broad consensus, which is notoriously difficult to achieve.
2. 2.Dormant funds: A significant proportion of bitcoins (estimated at around a third of the total) is stored in old addresses, including the one million bitcoins allegedly held by Satoshi Nakamoto. These funds could become inaccessible or vulnerable.
3. 3.Technical constraints: With around 170 million UTXOs (Unspent Transaction Outputs) on the Bitcoin network, migrating to new addresses would pose major network congestion challenges.
4. 4.Security/accessibility balance: A balance must be struck between securing the network and allowing users to access their funds.

Google's revelation regarding the potential to break cryptographic systems more easily using quantum computers represents an important warning for the cryptocurrency ecosystem.

However, this is more of a technological race than an immediate threat.

On the one hand, quantum computing development is progressing, albeit at a pace that is difficult to predict with accuracy.

On the other hand, the cryptographic community is actively working to develop and deploy solutions capable of resisting these future threats.

What is certain is that the Bitcoin and cryptocurrency ecosystem will have to adapt to survive the quantum era. The good news is that this adaptation is already underway, with concrete proposals and active research. The question is no longer whether Bitcoin will be able to resist quantum computers, but rather how and when this transition will take place.

For the average user, *there is no cause for immediate panic*, but it is prudent to stay informed and follow developments in this fascinating field where cutting-edge technology meets the financial systems of the future.