Bitcoin developers are debating how best to combat the rise of quantum computers with the power to break the cryptography that underpins the $2.2 trillion network.
In May, Tadge Dryja, a co-inventor of the Bitcoin Lightning Network, proposed adding a feature that will protect Bitcoin held in users’ wallets if a quantum computer-armed actor attempts to break their cryptography.
“It would be nice to have a way to not deal with this issue until after [quantum computing] shows up,” Dryja said in a post to the Bitcoin developer mailing list.
“My hope is that this scheme would give some peace of mind to people holding Bitcoin, that in the face of a sudden [quantum computing], even with minimal preparation, their coins can be safe at rest and safely moved.”
Reignited debate
Developers have long disagreed on if and when quantum computers will threaten Bitcoin’s cryptography. But recent developments in the field have reignited debate.
In December, Google unveiled a new quantum computing chip called Willow, which boasts a 56% improvement over the tech giant’s previous chip.
Then in February, Microsoft announced its own chip that it says solves the scaling issues that have persistently plagued the field.
Others, like Strategy Chair Michael Saylor, are unconvinced about the threat.
“I don’t worry about it,” Saylor told Bloomberg News this week. “Microsoft and Google market their quantum projects, but they would never sell a quantum computer that cracked cryptography as it would destroy their own companies.”
What is the issue?
Still, a growing number of voices warn that quantum computers may eventually threaten all cryptography and encryption.
In the immediate future, older Bitcoin wallets that use an outdated form of cryptography will be the easiest for quantum computers to crack.
This is a problem because such wallets hold millions of Bitcoin, including Bitcoin creator Satoshi Nakamoto’s $120 billion stash.
When an older wallet sends a transaction it reveals a vulnerable public key. A quantum computer could use that key to break the wallet’s encryption and steal the Bitcoin inside it.
Dryja’s solution is to require such wallets to make a so-called commitment transaction followed by a reveal transaction in order to move funds.
This should protect the wallets from attack, and only requires a relatively unobtrusive network update called a soft fork to implement.
Dryja isn’t the first to propose such a feature. Tim Ruffing, a cryptographer and blockchain researcher laid out an early version of such a system in 2018.
The situation is part of a broader debate among developers and stakeholders over whether the Bitcoin in older wallets should be shielded from attack — even if that means violating owner’s property rights — or left to eventually be stolen by those controlling quantum computers.
“I don’t see why old coins should be confiscated,” Hunter Beast, a Bitcoin developer said. “The better option is to let those with quantum computers free up old coins. While this might have an inflationary impact on Bitcoin’s price, to use a turn of phrase, the inflation is transitory.”
Yet others assert letting such a situation play out would have a dire impact.
“I cannot see how the currency can maintain any value at all in such a setting,” Pieter Wuille, a Bitcoin Core developer and the co-founder of Blockstream, said.
To be sure, many Bitcoin users have already moved their funds into newer wallets with stronger encryption. It’s a relatively simple process.
But Bitcoin wallets whose owners have passed away, lost the password-like keys that control access to the wallets, or have simply lost interest in Bitcoin, will always remain a target for cryptography-cracking quantum computers.
