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Quantum for Blockchain: threat or opportunity?



Author: Daniel Travaglia


Quantum computing seems to take a step closer to the reality every single day. For those who are not aware of this term, “quantum computing” is an alternative way for computers to represent computational memory and so to perform calculations. In traditional models, the information stored in the memory is represented through a sequence of bits that can take clearly defined values: either 0 or 1. The “bit” represents the unit of memory and it is used to measure its size in terms of how many bits are necessary to represent the current state of the memory itself (sequence of 0 and 1). Quantum computers instead use “quobit” (quantum bit) to represent the state of the memory. One of the properties of the quobits is called “superposition”, for which such bit can take both values 0 and 1 at the same time. This property allows the number of possible states bits can take to grow exponentially, so to scale up the space of solutions for a specific problem that is undertaken by a machine with such architecture.

One might ask what such computing milestone has to do in the realm of blockchain?

In order to answer such question, we need to recall the fundamental of this technology. One of the key characteristic of the blockchain is the immutability of the data stored in the ledger. This is granted by cryptographic algorithms that have been proven to be efficient for classical machines, but have failed in recent quantum-resistant test. The main reason for such failure is that, while with classical architectures brute-force attacks require an unfeasible amount of time to decrypt the key and overpass the system, with quantum computers this is not the case. The larger amount of computations that such architecture can perform with respect to traditional computers exposes the previously mentioned algorithms to a series of threats that cannot be underestimated when you want to set up an infrastructure involving some kind of encryption/decryption processes, such as blockchain. 

To give a more realistic representation of the problem, in recent times Google quantum research team has been able to perform a test computation that would have taken thousands of years by the most performing supercomputer available today in just 200 seconds. However, the same team has collaborated with some of the most prestigious private and public institutions to come up with quantum-resistant cryptographic algorithms that would almost certainly replace the current used ones when a post-quantum era will become a reality

On the other side, blockchain is known to be extremely slow when it comes to process transactions. Those mainly consists in validating and then storing the information on the distributed ledger while maintaining integrity in the system. Usage of quantum computers as node validators could represent an enormous opportunity to speed up the whole process while simultaneously give the opportunity to many other businesses that were reluctant of using blockchain due to its slowness in processing transactions to exploit its potential for their own businesses. This could potentially lead to new applications and use cases for which blockchain was not particularly suitable before (e.g: financial transactions)

Overall,such development represents an impressive leapfrog in the scientific and technology space, but at the same time raises some concerns, especially for security matters. The latters cannot be disregarded when it comes to build a blockchain infrastructure, and this would be probably one of the many reasons for further research and ulterior developments  in the quantum field.

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