Ethereum will not hide from quantum computers behind the PoS shield

Source: Adobe / Bartek Wróblewski

Quantum Computing has long been considered the “bogeyman” of Bitcoin (BTC). The widespread fear is that quantum computers, as secure as Bitcoin and other proof-of-work cryptoassets are in relation to standard cryptography, could provide additional means to destroy them.

Another popular assumption is that cryptoassets like Cardano (ADA), Polkadot (DOT), and Tron (TRX) (and finally Ethereum (ETH)) don’t use proof-of-stake cryptoassets as they don’t use PoW, which is equally vulnerable to Quantum computer attacks such as networks like Bitcoin, Bitcoin Cash (BCH) and Litecoin (LTC). According to a large number of computer scientists and crypto experts, however, it is not the consensus mechanism of a coin that poses the greatest risk in relation to quantum computers, but the signature system.

In other words, since the vast majority of PoS cryptoassets also use (non-quantum-related) cryptographic signature systems to sign individual transactions, they are almost as susceptible to quantum hacking as their PoW competitors. However, sufficiently powerful quantum computers are still a long way off, and their emergence is likely to stimulate a widespread shift to post-quantum cryptography.

51% attacks and signature attacks

The important point when considering whether PoS is less vulnerable to quantum computing is that there are two mechanisms a quantum computer could use to breach a crypto asset:

  1. The mechanism by which the right to publish a block of transactions and achieve a distributed consensus is obtained (e.g. PoW or PoS)
  2. The mechanism for authorizing individual transactions (usually with a signature system for public / private keys)

It is the first mechanism that affects PoW more than PoS. Bitcoin and other proof-of-work coins are theoretically vulnerable to a 51% quantum computerized attack.

However, Marek Narożniak, a PhD student in physics at New York University who worked with Prof. Tim Byrne on research into the quantum computer, explains that talk of a 51% attack by quantum computers is still theoretical.

“If someone has a large enough quantum computer and wants to perform a 51% attack – which is to outperform the remaining miners and produce invalid blocks – it would have to be a really massive quantum machine. The reason for this is that Bitcoin’s proof-of-work is based on a hashing function for which no efficient quantum algorithm is known [that can reverse it]”He said to

While Bitcoin’s weakness compared to PoS cryptoassets is still pretty hypothetical, quantum computing poses another threat that affects PoS and PoW alike.

“Even if consensus does not require cryptographic ‘work’ [in the case of PoS] It is still based on cryptography, which is currently mainly based on elliptic curves that are prone to quantum algorithms. An attacker with sufficiently powerful quantum computers could break the signatures of other validators and still mess up the consensus, ”said Narożniak.

This is a concern that has been confirmed by other commentators. In an analysis published by Deloitte, Bram Bosch wrote that around four million bitcoins are stored in addresses that use p2pk and p2pkh scripts, which are susceptible to attacks via quantum computers.

“Currently around 25% of the bitcoins in circulation are susceptible to a quantum attack. Even if your own bitcoins are safe, it can still have an impact if other people fail (or cannot take) the same protective measures, ”he told

Again, vulnerable scripting can potentially affect both PoS cryptoassets and Bitcoin, even if quantum computers are nowhere near generally available. And even without older schemes like p2pk (h), Shor’s algorithm – an algorithm for quantum computers – could be used to destroy many public key cryptographic systems.

“If you have a sufficiently large and reliable quantum computer, it is possible to break the digital signature that is used to sign Bitcoin transactions. Such a person could use the modified Shor algorithm to sign transactions where other people’s coins are transferred at will, ”said Marek Narożniak.

He added that the worst part of it “is that it couldn’t even be detected” and that PoS is just as vulnerable as PoW: “It would still be possible to generate transactions by breaking cryptographic signatures and creating transactions with someone else’s expenses become. ”

Quantum Resistant Solutions

Fortunately, current cryptographic research is more than aware of the theoretical threat posed by quantum computing, so you probably shouldn’t start selling all of your crypto just yet.

Researchers at Imperial College London published a paper in 2019 describing a protocol that would enable Bitcoin users to “securely shift their funds from non-quantum-resistant spending to those who adhere to a quantum-resistant digital signature scheme”.

In September 2020, Australian computer scientists from the Monash Blockchain Technology Center and CSIROs Data61 developed the so-called “world’s most efficient blockchain protocol that is … secure against quantum computers”.

So solutions seem to be available should a functioning quantum computer emerge that could realistically be used to threaten PoW and PoS crypto assets. And for most commentators, it is more likely that existing cryptos will use post-quantum algorithms than that new post-quantum cryptoassets will take their place.

“I think the latter scenario, in which existing cryptocurrencies are switched to use post-quantum cryptography, will be far more likely,” said cryptocurrency journalist and analyst Roger Huang. “It occurs to me that it will be much more difficult to rebuild the legitimacy, network effects, and exchange / exchange volume of something like BTC from scratch than if BTC only applies post-quantum cryptography.”

For Bram Bosch, it may be some time before the Bitcoin community (or another) is forced to actually implement solutions for quantum computing risks.

“The threat of a quantum attack would have to be very obvious and serious before the Bitcoin community can reach consensus on this matter. It is difficult to predict whether such a threat would arise suddenly or gradually and, as such, whether there would be time to act at all, ”he said.

This is exactly what is interesting about the danger that quantum computers bring with them: It is an unknown, unpredictable quality. However, since this poses a risk to the signatures used by almost all cryptoassets, we know that this poses a threat to PoS and PoW cryptos.
Learn more:
Bitcoin price could hit USD 1 million sooner than a quantum computer attack
– Can Quantum Computing Kill Bitcoin?
– Cryptosecurity in 2021: More threats to DeFi and individual users
– Crypto Tech in 2021: focus on scalability, data protection and usability
– Proof of Disagreement: Bitcoin’s Work vs. Ethereum’s Planned Staking
– Here are the ways governments could attack Bitcoin – and none of them sound hot

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