# Will quantum computing break down all DLTs?

A recent study proved that quantum computing will challenge today’s strongest encryption algorithms, much sooner than expected. This is quite a breaking news and should worry any organization looking forward relying or cryptography to secure data over +25 years. This is a serious threat for today’s rapidly growing distributed ledger technologies.

Source: BQ Intel

# Basic facts about quantum computing

Every day, we produce 2.5 exabytes of data. That’s 1 billion gigabytes, roughly equivalent to the content on 5 million modern laptops. There are more and more need to process them in the big data era where data is the new oil.

However, processing power and speed is a bottleneck for organizations. As Microsoft’s CEO Satya Nadella said, the world is running out of computing capacity as Moore’s law is kind of running out of steam. Practical mastery of quantum computing, the Graal of computer scientists, is expected to make it possible to easily process all that data with huge benefits for businesses and society at large.

While conventional computers leverage electronic circuits processing binary digits called “bits” (0 or 1) as the very basic element of information, a quantum computer uses quantum bits, called as “qubits”.

Qubits can basically exist in both 0 and 1 states simultaneously. Thus, they exhibit properties of quantum entanglement. Simply put, it’s a phenomenon where groups of particles cannot be measured independently.

It comes with exponentially faster computing power provided you know how to build quantum algorithms. An example of such ai Shor’s algorithm. Theoretically, there are also interesting applications for the nonrepudiation, the integrity and the confidentiality of data.

# State of art of quantum computing

David Deutsch, a physicist at Oxford University, claimed that a quantum computer of 300 qubits would be able to perform calculations faster than a digital computer bigger than the observable universe itself. Fairly mind blowing if true, yet we are very far from there.

IBM presented the first commercial quantum computer, IBQ System One featuring 20 qubits, at CES 2019 in Las Vegas.

In May 2019, Microsoft released an e-learning program aimed at building quantum algorithms using Microsoft’s Q# language.

# Impact for DLTs

Current encryption systems are not strictly tamper proof. Scientists simply rely on the enormous amount of time and energy that would be necessary for a digital computer to break down encryption keys. In other words, encryption systems such as those used in DLTs are designed such that breaking them is too time and energy consuming that they can be called tamper proof.

Up to now, cybersecurity experts estimated that it would take few decades for a quantum computer to break a 2048-bit RSA encryption. However researches from Google’s Craig Gidney and Martin Ekera from KTH Royal Institute of Technology show that by optimizing the most difficult operation of Shor’s algorithm, and using “only” 20 million qubits, 8 hours would be enough.

Consensus algorithms in DLTs dot not use RSA encryption, but one-way hashing functions. Some examples are SHA-256 in Bitcoin’s PoW, Ethash’s KECCAK-256 in Ethereum’s PoW, or Equihash in Zcash’s PoW. Yet the time efficiency of quantum computers fromo latest research indicates that it would be exponentially easier for miners to forge blockchains.

One implication is that the first to apply quantum power in PoW will have more hashpower than any other miners altogether, allowing him to consistently run 51% attacks successfully. Considering the tremendous expected increase in network’s difficulty, it would allow him to mine all new blocks alone and decide deciding which transactions are added or not. It will be the end of effective decentralization.

Even worse, a quantum miner would eventually steal all crypto-assets ever created by quickly forging bigger blockchains with hacked transactions from scratch. As soon as his own chain will become bigger, all other nodes will align on it per design.

Thankfully, it seems that cybersecurity experts have design encryption standards that even a quantum computer would not be able to break down.

**Check the full version of **__Blockchain Quarterly__** (Q1 2019) report for more Insights.**