According to Alexander Leishman, CEO of bitcoin financial services company River, it is not true that quantum computing would break all computer systems, including the global banking system. Leishman says that while this debate is fair, it is important to understand that not all systems are equally exposed and meet the same conditions. 

Leishman explains that Bitcoin is a unique system because access to a private key is equivalent to access to money. Quantum computing would allow access to such private keys by solving the “discrete algorithm problem,” a mechanism of elliptic curve digital signature encryption (ECDSA). 

In short, this means that “there is no layer of protection for any address with a revealed public key,” according to Leishman, who also comments that this is “by far the highest ROI+ attack you can perform if you have access to quantum computing.” 

Leishman goes on to say that the banking system couldn't work more differently than Bitcoin. While they don't have the quality of decentralization, a highly desirable characteristic of Bitcoin, they do have several additional layers of security around their computer systems.  

While quantum computing could break HTTPS, an attacker would still need to intercept traffic and perform DNS hijacking to get started. In many ways, quantum computing would take us back to the pre-HTTPS era of the Internet, which didn't completely collapse. The reality is that the connection between your computer and your bank is reasonably secure, even if it's not encrypted. 

Alexander Leishman, CEO of River

Leishman notes that banks would be more protected in a quantum scenario because, one, they use layers of security beyond public-key cryptography , and two, these layers can be combined and added on top of each other. For example, they use IP whitelisting and symmetric password authentication.  

Symmetric key cryptography is said to be less vulnerable than public key cryptography. However, more recent studies have shown that quantum computing does pose a considerable threat to symmetric cryptography, according to researchers at Tsinghua University. 

KYC controls, but ensures 

Leishman then emphasizes that compliance rules would ensure an extra layer of security by recording the identity of all users of the banking network, something that bitcoin, which is pseudo-public and privacy-first, does not do: 

Even if an attacker were to manage to breach a bank, they would need to move the money somewhere. Everything is tightly controlled with Know Your Customer (KYC) procedures and manual checks around large movements of funds. Good luck moving millions or billions without a human catching you. 

Alexander Leishman, CEO of River

River’s CEO closes the discussion by commenting that “a quantum computer won’t magically give you access to all the money at Goldman Sachs, but it could give you access to many billions of dollars worth of Bitcoin.  

While Leishman does not believe this threat is viable in the short term, he does feel it is important to discuss the issue honestly. 

Is Microsoft accelerating the quantum threat? 

Microsoft's new quantum chip, Majorana 1, has been a significant advance in the race for quantum computing, according to some experts.  

One of them is Fabrizio Micucci, who exclusively told a media outlet that with Microsoft’s announcement of the Majorana 1 quantum chip, “the timeline for large-scale quantum computing has been greatly shortened, which could spell trouble for the security of cryptocurrencies.”

Majorana 1 produces more stable qubits than traditional ones. Source: Microsoft

The Majorana 1 chip is powered by the world’s first “topological core architecture,” Microsoft says. The technology company hopes the chip, which uses a type of material called a topoconductor, will “make quantum computers capable of solving meaningful problems at an industrial scale a reality in years, not decades.”  

The Majorana topological core would allow the creation of more stable and less error-prone qubits (information units called topological qubits) than

Satoshi Nakamoto, the creator of Bitcoin, had already foreseen the possibility of quantum computing threatening the world's most important digital currency protocol.

In the event that the SHA-256 algorithm is compromised, the community could agree to build a new hash function or an improved version of it that is quantum-resistant. 

In some remote and unlikely case, Bitcoin could also move to symmetric key cryptography, although this is not compatible with its philosophy that exalts and allows pure custody, which is only possible through exclusive, individual and asymmetric possession of the keys.