The main feature of the blockchain is that its structure guarantees that the information stored is not being tampered with by third parties, thanks to a system of keys that allows almost inviolable security.
And in all these years, particularly the main and decentralised blockchains, have proved their inviolability. But could quantum computers change all this?
This system works as long as there is no such computing power that could allow a brute force attack, which would result in the funds being at risk. Until now similar technologies have never existed, however, now the situation has changed.
Blockchain vs Quantum Computers: is it a real problem?
With the advent of the first quantum computers, the issue has become relevant in the crypto environment, because it is thought that these computers could in the future create quite a few problems to blockchains and the related cryptocurrencies.
The first requirement is to explain briefly what a quantum computer is and how it works. Unlike traditional computers, quantum computers process sequences of bits 1 and 0 and have the ability to operate at the same time 2 different pieces of information thanks to the use of quantum bits (qubits).
Basically, Qubits instead of Bits allow performing several calculations in parallel rather than sequentially.
But this, as explained also by Giacomo Zucco, would not affect mining.
In fact, bitcoin has been partially conceived as quantum resistant: a quantum computer could not retrieve the key of a bitcoin address starting from the address itself because it is a hash and thus it’s not possible to retrieve the original source.
This is the case with bitcoin. But what about other cryptocurrencies?
Most cryptocurrencies, the so-called altcoins, are derived from the bitcoin source code and with appropriate updates they can become quantum-resistant without any problems.
For example, Ethereum already in 2015 had taken this into consideration and implemented Lamport signatures; the same goes for EOS, whose CTO, Daniel Larimer, said that it would be enough to simply update the protocol to avoid problems.
Are there blockchains and cryptocurrencies that are quantum-resistant?
The answer is yes, as some use a different system of signatures and hashes.
IOTA, which is a DAG (Directed Acyclic Graph) based cryptocurrency, has a single-use signature system, Winternitz, instead of the elliptic curve signature;
Nexus (NXS) uses a 571-bit private key and 1024-bit algorithms for the hash (Skein and Keccak);
Quantum Resistant Ledger (QRL) implements Lamport-Diffie, Winternitz and XMSS (eXtended Merkle Signature Scheme).
In conclusion, quantum computers are not able at present, but most likely also in the near future, to compromise the resilience of blockchains and cryptocurrencies.
Indeed, even if Google’s supercomputer has reached 53 qubits, these values are not enough to perform such a task.