Lightning Network: Not Helplessly Broken, Quantum Threats Overhyped?

by

The Lightning Network isn’t ‘helplessly broken’Opinion

A recent post by Udi Wertheimer gained a lot of attention in the crypto world, claiming the Lightning Network would be fundamentally unusable if quantum computers become a reality, and that there’s no way to fix it. This news quickly spread, and for companies currently using or considering Lightning for payments, it raised serious concerns.

It deserves a measured response.

Ethan Wertheimer is a well-known Bitcoin developer, and he’s right to be concerned: powerful quantum computers could eventually threaten the security of Bitcoin and the Lightning Network. This is a valid concern that Bitcoin developers are actively addressing. However, claiming Lightning will be “completely broken” by this is an oversimplification. Businesses planning for the future deserve a more accurate understanding of the risks.

What Wertheimer got right

Lightning payment channels need users to exchange public keys when setting up a connection. If powerful quantum computers become available, someone could potentially use those keys and a technique called Shor’s algorithm to figure out the private keys, and then steal the funds.

This is a real structural property of how Lightning works. What the headline leaves out

The danger isn’t just a general risk of losing funds; it only happens under certain specific circumstances, unlike simply saying someone could lose their Lightning balance.

Lightning channels are secured in a few key ways. While a channel is active, it’s protected by a cryptographic hash. Funding transactions use a special type of transaction (P2WSH) that hides the public keys used to control the funds on the blockchain. Payments within the network also use hashes and time-locked contracts, meaning the underlying keys aren’t visible. This design ensures that even if someone were secretly watching the blockchain, they wouldn’t be able to see the keys needed to steal funds, even with a powerful quantum computer.

The time frame for a successful attack is very limited and happens right after a channel is closed. Once the closing transaction is public on the blockchain, the details of the channel, including a standard public key, become visible. However, the person who closed the channel can’t instantly get their money back. A built-in delay, usually around 24 hours (144 blocks), needs to pass first.

If quantum computers become a reality, someone monitoring the Bitcoin transaction pool could identify a confirmed commitment transaction and use it to reveal the associated public key. They could then use Shor’s algorithm to calculate the private key and try to spend the funds before a time limit runs out. Specifically, outputs created when forcibly closing a Hash Time Locked Contract (HTLC) can create brief opportunities for attack – sometimes lasting only around 40 blocks, or about six to seven hours.

This is a genuine security flaw, but it’s difficult to exploit. An attacker would need to quickly solve a very complex mathematical problem for each piece of data they want to steal. It doesn’t involve a widespread, automatic drain of funds from all Lightning wallets at the same time.

The quantum hardware reality check

You won’t see it reported often, but powerful quantum computers capable of breaking today’s encryption don’t exist yet, and building them is a huge challenge – we’re a long way off.

As an analyst, I’ve been following the quantum threat to Bitcoin closely. To actually break Bitcoin’s security, someone would need to solve an incredibly complex mathematical problem – specifically, the discrete logarithm of a 256-bit key. This is like factoring a massive 78-digit number, and it would require a quantum computer with millions of stable qubits running for a considerable time. While there’s been progress – we’ve factored the number 21 and, more recently, a 90-bit RSA number using a combination of quantum and traditional computers – these achievements are still a tiny fraction of what’s needed to threaten Bitcoin. We’re talking about a difference of roughly 2 to the power of 83 – a truly enormous gap.

Google is making genuine progress in quantum computing, and it’s a field to keep an eye on. Experts predict we could see practical quantum computers as early as the late 2020s, though some think it will take until the 2030s or even longer. Regardless, this isn’t an immediate threat like a security breach.

The development community is not sitting still

Honestly, I think it’s a bit off to say Lightning developers are ‘helpless,’ like Wertheimer suggests. Just since December, the Bitcoin community has been really active on the post-quantum front. We’ve seen some serious proposals come out, including SHRINCS – which is incredibly small – and SHRIMPS, which is designed to work across multiple devices and is much smaller than current standards. Plus, there’s BIP-360, Blockstream’s work on hash-based signatures, and proposals to integrate OP_SPHINCS, OP_XMSS, and even STARK-based opcodes into Tapscript. It’s clear a lot of progress is being made.

It’s not that Lightning Network is flawed or beyond repair. The real issue is that, similar to Bitcoin and much of the internet’s security systems, it needs fundamental updates to protect against the future threat of quantum computers. Fortunately, those updates are already being developed.

What this means for businesses building on Lightning today

Lightning Network is currently processing substantial payments for established businesses – including online gaming platforms, cryptocurrency exchanges, new digital banks, and payment processors – enabling them to move money around the world quickly and at very low cost. Instead of worrying about potential future risks, businesses should focus on whether the teams developing the Lightning Network are proactively addressing upcoming challenges and preparing for the future.

Considering the amount and strength of research into post-quantum cryptography within the Bitcoin development community, the answer is yes.

The Lightning Network isn’t failing. Like all digital financial systems, it has potential long-term security challenges, but a dedicated team of developers is actively working on solutions. This is a more accurate picture than some recent reports have suggested.

Read More

2026-04-18 19:37