The world we live in these days is defined by how fast can technologies evolve, and how well can we adapt to their evolution. From storage units to processing power, we are, to a certain point, obligated to make the best out of the latest iterations in order to keep this progress going.
But, at this moment, some of us are at a crossroads. Given that the current state of blockchain is entirely based on the processing limitations of hardware to properly encrypt the data that’s stored in the blocks, a big step forward like quantum computing poses a threat to this system. What are our options? Is the future of blockchain as grim as it seems?
Taken from phys.org
A Quick Rundown
To visualize the threat posed by quantum computing, we must first understand clearly how blockchain relies on today’s limitations in processing.
Taken from hackermoon.com
Current cryptographic systems are based on how long it takes for a computer to find a solution to a quite complex mathematical problem, and the strength of a certain system is measured in said time. The longer it takes to a certain computer to find the solution to the problem, the safer the encryption system is. The current system used in blockchain is a mix of RSA (Rivest-Shamir-Adleman, a mathematical problem where the computer must find two primes that are factors of a given large number) and ECC (Elliptic Curve Cryptography, a mathematical system that allows for smaller encryption keys than RSA, but also leaves less room for error).
On top of these two systems we have built most of the current blockchain systems. For example: Bitcoin addresses are 160-bit hashes of an ECDSA (Elliptic Curve Digital Signature Algorithm), and each one of these is linked to a signature used to confirm transactions from and to it. ECC is also used by many blockchains due to the ability to reach considerably high security levels with short keys.
Now, these mechanisms only work due to how long it takes for our current hardware to solve the mathematical problem associated with the encryption. When a new technology comes forward that allows for increasingly faster processing times, these algorithms will shortly become obsolete, and quantum computing seems to be that new technology.
A Brief History of Quantum Computing
Computers as we know them now work on binary bits, the smallest unit of data, which can take values of 0 and 1. With bits as building blocks, every computational system we know today was able to be built, and that is the way it has been since the dawn of computation. But, as time goes on, more and more complex problems arise that will eventually require computing capabilities beyond those achievable with traditional bits.
Quantum computers fix this issue by taking advantage of three principles of quantum physics: superposition (a simultaneous combination of two states of a particle at the same time), entanglement (a phenomenon where two particles behave together as a particle even when they are physically apart from each other) and interference (similar to wave interference, the states can add up when their phases are synchronized).
Taken from towardsdatascience.com
Based on these principles, quantum computers can quickly find solutions to problems that require multiple iterations across different states of certain variables. A good example is to calculate the bond length that results in the lowest energy state within a molecule, a problem that requires to iterate across a huge variety of lengths and calculate their energies.
Quantum bits (qubits) are perfectly fit for this task given their property of superposition of states. The aspects of the state of each qubit is then measured and traced back to a degree of energy of the molecule. Iterating multiple times on this basis will eventually lead to the desired bond length, which represents the most stable state of the molecule.
The Weak Spot
We can build a similar example for cryptographic keys. If a quantum computer can create a “quantum key” that holds several states simultaneously, then iterate over little variations of said states to reverse-engineer the key, thus completely breaking the encryption mechanism and making the whole system obsolete. Thus, there is a looming fear of these systems becoming available enough for potential attackers to use them against the blockchain-based decentralized networks we have come to build.
But the future does not look as dark as it seems. The National Institute of Standards and Technology (NIST) is already reviewing potential solutions for post-quantum cryptography to set them as standards for future projects and have already identified 26 possible candidates. However, most of these potential solutions come with issues that may hinder their adoption, like scalability due to the use of large keys and non-reusability of keys resulting in eventually running out of possibilities.
At this point, it is impossible to know which of these candidates, if any, will be the most widely adopted, or whether its adoption will be enough to counter the potential of quantum computers and their increased abilities in simultaneous processing. The NIST has a very important task in their hands, but each one of us should be prepared for when we enter the quantum era, and to support the process of adaption if we intend to keep implementing blockchain as we know it.