Quantum Computing vs. Blockchain: A Threat to the Digital Ledger?

    We’ve all established that the blockchain is the new breakthrough technology eating up the whole Web3 ecosystem. These distributed peer-to-peer digital ledgers are revolutionizing how we store and exchange data. This technology has been the foundation of significant cryptocurrencies such as Bitcoin and Ethereum, and a groundbreaking basis for non-fungible tokens (NFTs). But this newfound technology might be facing a threat – Quantum Computers.  Quantum computing vs. blockchain is a real and very pressing matter that blockchains need to tackle. 

    One of the many features of the blockchain that make it gain much attraction is its immutability and top-notch security. No one can break the blockchain. Or can they? Do you think your crypto and valuable NFTs are safe from the beast of all technological advancements? Can they be safe from physics? Have you ever considered that Einstein and Bohr might be the reason why you lost all of your belongings? 

    Okay, let’s chill. For now, it’s all theoretical. However, let’s see how quantum computing can become a threat to blockchain technology. 

    What is a Quantum Computer?

    Before we freak out and announce that the world of crypto is crumbling, let’s take a moment to understand what is quantum computing and how it works. 

    Quantum computers are devices that apply the obscure phenomenon of quantum mechanics to generate huge processing power. This type of computing can solve large or complex computational problems that a regular computer fails to solve. Laws such as entanglement, interference, and superposition of encoding can make a quantum computer reach the point of supremacy, which even the most powerful supercomputer can’t fathom comprehending. 

    So it’s basically a computer that runs on physics. Since we might not all have a physics degree lying in our pockets, I’ll try to simplify how a regular computer differs from a quantum one in order to understand its effects on the blockchain. 

    Bits vs. Qubits

    Here’s an analogy explaining the difference between a regular computer’s bits and a quantum computer’s qubits. 

    Consider you a have pair of coins with regular heads and tails faces. You flip them. The possibilities of the states of the coins are Heads-Heads, Heads-Tails, Tails-Heads, and Tails-Tails. That’s how a regular computer process information and carries out computations using long strings of binary digits that are represented by 0 and 1, known as bits

    In this case, the computational possibilities of two pairs of bits are 00, 01, 10, and 11. The output can never be all possibilities at once. That’s where quantum computing comes in with its own version of “bits”. 

    Now you have two coins with both faces are heads. You flip them.  How much time do you need to come up with all possible solutions? That’s right, no time at all. You already calculated the possibility of the result always being Heads-Heads. That’s how a quantum computer processes pieces of information, using quantum mechanics phenomenons, it uses qubits which are subatomic particles such as electrons or photons. 

    Qubits have quantum properties that make them have a larger processing power than the same power of regular binary bits. How? Well using the quantum mechanics’ concept of superposition, qubits can represent all possible combinations of 1 and 0 at the same time. Remember Schrödinger’s cat? The dead/alive cat at the same time? It’s something like that. Therefore, a quantum computer can always predetermine all possibilities beforehand, just like you did with the head-faced coins. 

    Qubits vs. Bits

    If you think about a computer that can generate all possibilities within seconds and demonstrate them at the same time is scary. Don’t make me even talk about the qubits’ entanglement or decoherence. The actual quantum computer looks like coming out of a Steampunk movie!

    Quantum Computing: A Blockchain Threat?

    So why is a quantum computer that uses these superimposed qubits a threat to the immutable blockchain? Well, let’s take a look at how the blockchain actually functions. 

    In order to secure transitions, the blockchain utilizes SHA-256 hashing cryptography. This cryptography protocol is based on encrypting wallets’ private keys using hashing functions. The SHA-256 hash is a long string of code that masks what’s behind it creating some sort of firewall that no one can break. 

    Consider it as a password for certain data. However, no one can break through this encryption. The hash is a one-way function, meaning it’s nearly impossible to reverse engineer it. You can easily create a hash from certain data but hard to retrieve the data from the hash. 

    Private Public Key Blockchain

     In the case of crypto transactions, the hash function is used in two cases. 

    • Encrypting Blocks:  Hash functions generate a long string of digits to encrypt a block of transactions. If someone somehow was able to break through the hash, they can alter the transactions. 
    • Encrypting Wallet Keys: Hash functions generate public keys from your private keys. Since the hash is a one-way function, there is no way to derive the private key from the public key. 

    In order to break the hash encryption, massive computational power is required to go over all possibilities, which a regular computer using the binary system cannot achieve. Quantum computers’ superimposed qubits can crack public keys and block encryptions. Although, it is still theoretical. Some debate that the SHA-256 hashing function is actually quantum-proof. Still, there are scientists who claim that quantum computers bend the logic of some encryptions.

    What Does it Mean to Investors?

    Does that mean that the crypto world is doomed in the never-ending cycle of technological advancement? Well, for now, there’s nothing to worry about. Before you go and withdraw your funds and sell your NFTs in mass hysteria, quantum computers are still in development. Meaning, the threat that quantum computers might be able to break through your wallet and steal your assets won’t happen overnight. In fact, it might take several years. 

    However, crypto and NFT investors should keep an eye out for this technological advancement, or any technology that might render the blockchain obsolete. Let’s not forget that the progress of quantum computing is simultaneously followed by the advancement of the blockchain. 

    Some programmers and projects are already working on post-quantum cryptography and other secure alternative methods. Therefore, investors might move their assets to a more secure type of storage and exchange platform that defies the abilities of quantum computing. 

    Quantum Attacks Against the Blockchain

    To discuss how the blockchain can mitigate quantum computing threats, let’s understand the two different types of attacks a quantum computer can target toward the digital ledger. 

    Storage Attack

    In a storage attack, a quantum computer can target vulnerable public wallet addresses that reside on the blockchain and reverse engineer the hashing function to access the private keys. In this case, funds can be stolen by a quantum computer with sufficient resources. 

    Storage Attack

    How many resources? Well, it’s estimated that these attacks would require almost 10 million qubits, far more than what quantum computers can operate today. However, scientists believe that 10 million qubits can be easily reachable in about 10 to 15 years. So you can relax for the next 10 years knowing that your crypto is safe and sound. However, in this span, many other technological advancements can emerge, so always keep an eye out. 

    Transit Attack

    Transit attacks are less likely to happen in the near future. In order to perform a transit attack, a quantum computer would have to hijack a blockchain transaction in transit and redirect the funds to another address. Meaning, that there’s a small frame of time where a quantum computer can perform this attack since it has to be before the validation or processing of transactions. 

    Transit Attack

    Why is this less likely to happen? Because it requires large-scale quantum computing that needs billions of qubits! Even mitigating such an attack is hard since it requires a whole different encryption system or algorithm. 

    Quantum-proofing Cryptography

    Knowing that quantum computers would take years to actually become a threat to the blockchain poses an urgent question. Should the blockchain change some of its protocols for storing public addresses that would mitigate the storage attack? This way it would somewhat fix the threat of quantum computers. However, it will not offer a solution in the long run, seeing as the transit attack can happen sooner than we expect. 

    Or should the blockchain change the whole cryptography protocol and start developing a new post-quantum cryptography system? This solution can not only be a quantum-proof fix but a superior upgrade of security against any technological unknowns coming to render the blockchain obsolete. However, easier said than done.

    The decentralization of the blockchain makes approving a certain change protocol of this magnitude is quite hard since it requires consensus from all nodes. Moreover, since there is no central authority to update all private and public keys to a post-quantum algorithm, the responsibility will fall upon wallet holders to do the upgrades themselves. 

    The Bitcoin platform has addressed the issue of quantum storage attacks. They stated that mitigating such an attack is easy as long as the public key is not exposed. “However, the challenge is, how do you actually spend the funds?”

    Quantum-Proofing Signatures

    Both the Ethereum blockchain and the Bitcoin blockchain are experimenting with quantum-proof signatures. The problem of quantum computers performing a storage attack lies in how you digitally sign your transactions. You sign transactions by kinda saying that this transaction was made by the public key generated from a private key. Thus, exposing your public key to quantum computing attacks. Which is a big no no in the quantum world. 

    In this case, both blockchains are trying to implement the Lamport Signatures. This kind of signature kind of solves the problem without the need for the traditional public-key cryptographic system. I won’t go into the nitty-gritty of how these signatures work. But let’s just say that one public key will have 320 hashes instead of one elliptic curve point. However, this solution will only work if you use your public key once or twice. The third time you use it, the security of the Lamport signature will drop. 

    Other Solutions for Post-Quantum Blockchains

    Some projects are rising as quantum-proof blockchains or alternatives to blockchains from the get-go. Some projects are trying to create a quantum-proof technology that would act as an added layer of security to the blockchain. For example, Nillion, a web3 initiative is building a technology that doesn’t even use regular encryption. Instead of encrypting data behind hashing functions, Nillion divides data into unrecognizable particles that don’t reveal the underlying information. Thus, rendering traditional encryption obsolete in the future. 

    Nillion vs Encryption

    Quantum Computing vs. Blockchain

    Before you start a mass quantum freak out and start quantum-proofing your house like a mad conspiracy theorist, saying that the government is out to get us by using physics against us. It’s a long way to go before quantum computers actually get to 10 million qubits. Google’s ‘Sycamore processor’ quantum computer has only 53 qubits. However, it’s good to be always on the lookout for major technological advancements that might affect your digital assets. The quantum computing vs. blockchain debate is still a work in progress. In a sense, you could be Schrödinger’s cat. Both freaking out and not freaking out at the same time. 


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