3D render of weak link of a broken blockchain exploding
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Blockchain is just the latest technology that will change the way we work and live, but there is a new technology that is starting to emerge and, according to researchers, it looks set to disrupt the disruptor. That technology is quantum computing. Recently, a paper by computer scientists published in Nature magazine even goes so far as to suggest that blockchain could be made obsolete by quantum computing.

The scientists argue that, within a decade, quantum computers will be able to break a blockchain's cryptographic codes. Keeping in mind that by 2025, up to 10 percent of global gross domestic product is likely to be stored on blockchains, the size of the problem becomes clear.

What Blockchains Do

Blockchain is a structure for storing data in which groups of valid transactions, called blocks, form a chronological chain, with each block cryptographically linked to the previous one. While it has been widely associated with bitcoin and cryptocurrency, it also is increasingly used to store enterprise data.

Blockchain is first and foremost a public (or sometimes private or hybrid) database that is open and decentralized. Open means anyone can read it unconditionally, and anyone can write into it after meeting certain conditions. There is no governing body that can arbitrarily modify the data, nor is there a single point of failure from where the database could be hacked or destroyed.

Data in the blockchain can either be open or encrypted and readable only by those for whom it is intended. Quantum computing, however, could change everything.

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What Quantum Computing Will Do

Quantum computing poses a threat to blockchain technology because it upends the basic security assumption of elliptic curve cryptography, namely, that computers cannot factor large numbers effectively, said Adam Koltun, lead strategist for the cryptocurrency Quantum Resistant Ledger.

In today’s traditional and legacy blockchains, the most common form of public key/private key pairing is one based on the Elliptic Curve Digital Signature Algorithm (ECDSA). ECDSA works on the the security assumption that computers, even very powerful ones, cannot break down very large numbers in human amounts of time and break blockchain keys. Most legacy blockchains rely on ECDSA.

In ECDSA public-key cryptography systems, anyone can send transactions or messages to a public key, but only the holder of the paired private key can access what has been sent to the public key/address. It's like a mailbox — anyone can stick letters in through the front slot, but one needs the (private) key to open up the back and take anything out of it. “The security of a blockchain is guaranteed by its cryptographic functions, and the most common one in the industry is at risk in the face of quantum computing. Additionally, unlike centralized systems, decentralized systems need the active consent and participation of all users to achieve something like total address type migration, which is what would be necessary to achieve quantum resistance,” he said.

Related Article: 7 Trends Driving Blockchain Forward

Quantum Computing Limits

Alexander Leo-Hansen, founder and CEO of Coinbox.dk, a digital bitcoin/Ethereum seller, said that while quantum computing does pose a threat, it is not the only technology that is at risk. Banks, companies and countries using blockchain will be targeted if it develops to the point where quantum computers can unravel blockchain codes. But, he said, it won’t go that far. There are two reasons:

1. Enhanced encryption: Quantum Computing will soon be a reality. It can, and will be used to crack the current standard which is RSA. However, if quantum computing is applied to encryption, the encryption gets tighter and it becomes harder to break the blockchain codes.

2. Blockchain companies: IBM, Google and a number of other technology giants are the current movers in developing quantum computing. It is likely that they will not enable users of quantum computing to crack bank-encryption or blockchain. “To do so is illegal and would destroy those companies. I believe in the future every encryption [system] will be improved by quantum computing. Blockchain is improving day by day,” he said.

Theoretical Threat Goes Beyond Blockchain

In practice, quantum computing poses only a marginal threat, said Gabriel Bianconi, founder of Scalar Research and quantum computing researcher. Public-key cryptography is a common technique used for encryption and authentication. Internet connections (HTTPS), blockchains, and many other applications use this technique. In most cases, their security relies on hard mathematical problems such as integer factorization, which can't be cracked easily by a traditional computer.

In theory, a sufficiently powerful quantum computer would, however, be able to solve these problems efficiently. If that happens, he said, then the problem is much larger than just bitcoin — people would be able to crack most forms of cryptography used nowadays.  However, there are two reasons why this is not an immediate concern:

1. Quantum computing maturity -  This computing is still in its infancy. A sufficiently powerful quantum computer won't necessarily be available by 2025.

2. Quantum-safe algorithms - There are other cryptographic algorithms called quantum-safe or post-quantum algorithms that cannot be cracked by quantum computers. There are cryptocurrencies that are already experimenting with these technologies (e.g. QTUM). If quantum computing become a risk, bitcoin would likely transition to a similar algorithm.

Quantum Computing’s Long-Term Threat

Predicting the future is hard. Building a quantum computer is extremely challenging, but the potential to solve important problems that classical computers cannot solve is motivating large companies to spend a lot of time and resources to be the first to succeed at building one, and progress is being made quickly.

Tim Hollebeek, industry and standards technical strategist at DigiCert points out that unlike classical computers, quantum computers are best at solving certain very specialized problems. However, for those problems, they are far better than classical computers ever will be. Examples include simulating other quantum mechanical processes, solving complex interconnected equations for weather prediction or artificial intelligence, and factoring very large numbers.

It is likely that quantum computers that can solve interesting problems will emerge within the next few years. Ones that can threaten modern cryptographic algorithms are farther off, but could arrive as soon as seven to 10 years.

The most important danger is that both of the asymmetric cryptographic algorithms (RSA and ECC) that are the basis for all of the world's modern cryptography, are weak defenses against quantum computers. Now that effective quantum computers are becoming a reality, cryptographic systems will have to transition to new cryptographic algorithms that are designed to be strong against quantum computers."It is difficult to overemphasize the magnitude of this transition. Virtually all of our cryptographic software and hardware will need to be rebuilt and replaced over the next decade or two," he said. "It will be a long and complex process, and industry experts are working hard to prepare for this important transition."