- Hash-based signatures are a compelling way to make Bitcoin resistant to quantum computers, researchers say.
- How developers could implement them is subject to ongoing debate.
- Quantum computers are among the biggest threats to blockchain technology.
A cryptographic technique known as hash-based signatures could be the key to protecting the Bitcoin blockchain from the looming threat of cryptography-cracking quantum computers.
Quantum computers exploit quantum mechanical phenomena to solve complex problems exponentially faster than classical computers.
They are seen as one of the biggest threats to blockchain technology because their superior computing power could be used to crack the cryptography that keeps blockchains like Bitcoin secure.
In a revised paper published on December 5, Blockstream researchers Mikhail Kudinov and Jonas Nick examined several ways the $1.8 trillion Bitcoin blockchain could be upgraded to make it quantum proof.
The pair argue that hash-based signatures are a compelling post-quantum solution because their security relies solely on hash function assumptions similar to those already underpinning Bitcoin’s design.
“These schemes have undergone extensive cryptanalysis during the NIST post-quantum standardisation process, adding confidence in their robustness,” Kudinov said in an email to the Bitcoin developer mailing list, presenting his and Nick’s work.
NIST is the National Institute of Standards and Technology, a US government agency best known for its widely adopted cybersecurity frameworks.
Researchers have long disagreed on if and when quantum computers will threaten Bitcoin’s cryptography. But recent developments in the field have reignited debate.
In February, Microsoft announced a new quantum computing chip that it says solves the scaling issues that have persistently plagued the field.
Then in October, Google released new research which it claims brings quantum computing much closer to being used in real-world applications such as medicine and materials science — or swiping Bitcoin from holders’ wallets.
At the current rate of development, quantum computers could start threatening Bitcoin within five to 10 years, Pierre-Luc Dallaire-Demers, a scientist-in-residence at the University of Calgary, previously told DL News.
Vitalik Buterin, co-founder of the second-biggest blockchain Ethereum, sees the technology progressing even quicker. He warned last month that quantum computers could break Ethereum’s underlying security model before the next US presidential election in 2028.
What are hash-based signatures?
Hash-based signatures rely on hash functions, mathematical algorithms that are considered to be quantum-resistant because they aren’t easily cracked by quantum algorithms, unlike the public-key cryptography used for Bitcoin.
Hash functions can counter the brute-force searches made possible by quantum computers by simply increasing their output size, making the search space too large and keeping them secure for applications like digital signatures.
How exactly developers could implement hash-based signatures, however, is subject to ongoing debate.
Considerations such as keeping validation costs low, whether to standardise multiple hash-based signature implementations, and whether or not the entire network’s history should be necessary to validate transactions all need deciding.
The recent quantum proofing discussions follow a May proposal from Tadge Dryja, a co-inventor of the Bitcoin Lightning Network, to add a feature that will protect Bitcoin held in users’ wallets if a quantum computer-armed actor attempts to break their cryptography.
Older Pay-To-Public-Key Bitcoin wallets created before 2012 that rely on less secure cryptography will be the first to fall to quantum computers.
These vulnerable wallets, which include Bitcoin creator Satoshi Nakamoto’s $98 billion stash, contain approximately $600 billion worth of Bitcoin, per an estimate from Project Eleven, a startup aiming to secure Bitcoin against quantum computers.
“It would be nice to have a way to not deal with this issue until after [quantum computing] shows up,” Dryja said at the time.
Tim Craig is DL News’ Edinburgh-based DeFi Correspondent. Reach out with tips at tim@dlnews.com.
