Author: Jeffrey Hu, Source: Author's Twitter @jeffrey_hu
Will quantum computing destroy Bitcoin? This topic, which has a folk-scientific temperament, always causes a wide range of discussions/FUD every once in a while.
Will Google's newly released Willow be different this time?
We did a survey.
If we simplify the Bitcoin protocol, it can be divided into two parts: mining (based on hash) and transactions (based on elliptic curve signatures).
These two parts are indeed potentially affected by quantum computing: Grover's algorithm and Shor's algorithm.
But the current "computing power" of Willow is far from enough to affect both parts.
To attack Bitcoin hash and signature in a reasonable time, about thousands of logical qubits are needed
Depending on the process, several (possibly thousands) physical qubits are encoded into 1 logical qubit.
This means that to attack Bitcoin, about millions of physical qubits are needed.
Willow's physical qubit is 105, so there is still a long way to go.
But what if one day the computing power is sufficient?
For mining, the impact is relatively limited. Because the Grover algorithm is only accelerated, it does not reverse the hash law, and it still requires a lot of calculations to find the hash value required for mining.
It can be simply understood that there is a new powerful mining machine on the market.
For address signatures
Some addresses do need to be careful! These include the oldest P2PK and the latest P2TR based on public keys.
P2PKH, P2SH, P2WPKH, P2WSH are all in the form of hash, so they are relatively safe.
But be aware that reusing these addresses will also expose your public key, leading to risks.
Of course! Bitcoin is constantly evolving, and in the future, we can introduce, for example, hash-based Lamport signatures. There have been many discussions in the community, such as https://blog.blockstream.com/script-state-from-lamport-signatures/ (although it is used in state applications)
It is also possible to introduce quantum-resistant lattice-based passwords.
And these can be activated through soft forks.
In addition to developers, good usage habits can also effectively defend against quantum threats.
For example, change the receiving address each time (one-time one-password) instead of reusing the address (every time I talk about this, I want to complain about many of the current "Bitcoin ecosystem" wallets).
For example, before quantum computers can pose a sufficient threat, assets can be transferred to a relatively safer isolated witness address, etc.
Other networks, such as Ethereum, have also discussed post-quantum cryptography. These designs can also be introduced through hard forks.
But in the final analysis, the emergence of quantum computers can obviously affect more than just Bitcoin or other cryptocurrencies. Many important areas such as traditional financial systems, national defense systems, and confidential channels will be affected.
So in short: In the short term, we don’t have to worry about the threat of quantum computers to Bitcoin and other networks
- But it is strongly recommended to develop good usage habits and keep an eye on quantum progress.