What Does Quantum Computing Mean for Blockchain Security?

Blockchain developers pride themselves on the enhanced security features of blockchain technology. Yet, there is a major threat lurking at the back door that could make blockchains lew security. It’s called quantum computing.


What Is Quantum Computing?

Quantum computing is difficult to define because it involves a different way of thinking. In short, it’s a completely different paradigm in computing than current computing systems.


The assumption that quantum computing is faster than traditional computing is false. It isn’t faster, but it is more powerful. That’s because it relies on subatomic quantum mechanics. The challenge with subatomic quantum mechanics is that it takes place at the particle level, a physical state smaller than atoms. In other words, beyond the naked eye. Because quantum computing is based on quantum mechanics, it involves weird, unexplainable processes that defy logic and human intuition. The value in quantum computing lies in the ability to solve problems that we can’t currently solve using today’s best computing systems.


For instance, with cryptography, passwords and cryptographic keys are so long that modern computing systems could take forever to guess them. That’s because they are binary in nature. Information is processed as 1s and 0s, called bits. With quantum computing, information is processed in qubits.


Imagine a sphere. Draw a line from the top of the sphere, through the middle, to the bottom. The top of the sphere is ground 0 and the bottom is ground 1. Those two points are like bits. Now imagine the horizontal and vertical intersections along that sphere as measured in longitudes and latitudes. Qubits are where those longitudes and latitudes intersect along the sphere. This quantum measurement between 1 and 0 on the latitude scale coupled with the degree of longitude determines how calculations are performed in quantum computing.


That’s a bit simplified, but it’s the best we can do.


How Is Quantum Computing a Threat to Blockchain Security?


Currently, there are no quantum computers strong enough to bust through modern cryptographic security gates. But experts predict that it could happen within 10 to 15 years. Waiting until then to devise more secure cryptography will be too late. Cryptographic security engineers should start preparing now for a quantum computing world.


There are two types of threats cybersecurity experts are currently concerned about regarding quantum computing. More threats will likely emerge by the time it becomes a major issue.


  • Storage attacks – A storage attack involves breaking through vulnerable wallet addresses by knowing their public keys. The computing power needed to break security using a storage attack is estimated to be 10 million qubits. Current quantum computing systems are nowhere near that, but it could happen sooner than we expect.
  • Transit attacks – A transit attack is hijacking a blockchain transaction while in transit. This could be a bitcoin miner receiving his reward for discovering a new block or a customer sending a payment to a business on the Ethereum blockchain. The faster the transaction speed, the more difficult it will be for malicious actors to perform this kind of attack, but the threat could be a real threat in just a few years.


Cybersecurity experts are discussing how these threats should be approached. New cryptographic security measures may be necessary to prevent such attacks. New blockchain protocols that mitigate these risks may also be explored. For now, end users are largely responsible for their own security, and it bears reminding that the best security for cryptocurrency held in wallets is to store it offline in a cold wallet and only move it only when necessary. Even then, it is likely that cryptocurrency exchanges—centralized and decentralized—will become major targets when quantum computing matures enough that current cryptographic systems are too weak to defend themselves.

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