# Introduction to Quantum Cryptography – Everything You Need to Know

## The Need for Quantum Cryptography

To explain what I mean by Quantum Cryptography, I would first have to dive into what Quantum Computing actually is. I could say what “Expert” websites say, that Quantum computers use the fundamentals of quantum mechanics to speed up the process of solving complex computations, they can process massive and complex datasets more efficiently than classical computers. But that just sounds like a whole lot of gibberish and no-talk.

So, let’s take a bold step and try to breakdown what all that gibberish means.

## What is Quantum Computing?

Quantum computers could spur the development of breakthroughs in science, medications to save lives, machine learning methods to diagnose illnesses sooner, materials to make more efficient devices and structures, financial strategies to live well in retirement, and algorithms to quickly direct resources such as ambulances. Quantum computing is poised to upend entire industries from telecommunications and cybersecurity to advanced manufacturing, finance, medicine, and beyond.

In the simplest sense, a Quantum Computer is a computational device that uses the fundamental laws of Quantum mechanics. Unlike “classical” computers that are built ground up based on the classical laws of physics, a Quantum Computer is built using the principles of Quantum Mechanics which, in theory, allow computation to be exponentially faster than what could be achieved by computers today.

One of the easy ways to understand immense complexity and potential of Quantum Computing was put forward by IBM, the spearhead of the Quantum Revolution. IBM put forward a blog post by their writer Jan Lillelund, who simplified the concept in a manner by which even kids can try to understand what Quantum Computing means.

*Jan explains, “[Quantum Computing] will for sure solve complex problems in the future that even classical super-computers will never be able to. In life sciences, supply chain management, chemistry research, and much more ………… even our kids (need to) get familiar with quantum computing.” He adds later, “If more people get excited about the fascinating opportunities the technology offers, it will hopefully help to push the development of quantum computing to new heights in the future.”*

## Reliance on Modern Cryptography

Cryptography is the process of encrypting data or converting plain text into scrambled text so that only someone who has the right “key” can read it. Since millennia, cryptographic practices have been used to code and decode communication, thus ensuring privacy and secrecy. As the old cryptographic methods are broken, new ones take their place, being harder to solve and intercept.

With the advent of the Internet and the exponential increase in computing capacity, cryptographic algorithms which use encryption much more computationally intensive than any single computer can handle have been developed.

Today, Cryptography is an indispensable tool used to protect the information in computing systems. It is used everywhere and by billions of people worldwide daily. It is used to protect data at rest and data in motion. Every piece of hardware or software you use today is using some form of modern encryption that is unbreakable.

Unbreakable only until there comes an exponentially better infrastructure for computing, as we know it today.

## Will Quantum Computing Break Security as We Know It?

All around the world, Cybersecurity researchers, experts, and analysts are rightly worried that a new type of computing infrastructure – Quantum Computing, could break most modern cryptography, the backbone of all financial, economic, corporate and public data.

Think how efficient it would be if your phone is 10 times faster tomorrow than it is today. You would be able to build, design, and play much faster. What if your mining rig, that is of the highest configuration, is 20 times faster in finding hashes? You would easily find blocks and get the rewards while others are just waiting around. With Quantum Computing, this is ten to a whole new level.

If we design a Quantum computer to perform a particular task and that task only, it is estimated that we could see a computing reduction time from 10,000 years to a mere 3 minutes. If put to the task, it would break any algorithm or encryption that is feasible enough to break in minutes.

This existential problem poses a huge threat to the world of blockchain and cryptocurrency as well. All blockchains are built of hashing algorithms and public-private key encryption. These encryptions could be broken if Quantum Computers are scalable and put to everyday use. If quantum computers become real then someone may be able to reverse blockchain encryption in the future

## Introducing Quantum Cryptography

Quantum cryptography is the science of exploiting quantum mechanical properties to perform cryptographic tasks. Quantum cryptography, by extension, simply uses the principles of quantum mechanics to encrypt data and transmit it in a way that cannot be hacked. The best-known example of quantum cryptography is quantum key distribution which offers an information-theoretically secure solution to the key exchange problem.

Quantum cryptography, also called quantum encryption, applies principles of quantum mechanics to encrypt messages in a way that is never read by anyone outside of the intended recipient. It takes advantage of quantum’s multiple states, coupled with its “no change theory”. In simple words, the “No change theory” means that any encrypted communication cannot be unknowingly interrupted. This removes the drawbacks of classical encryption mechanisms that mainly depend on the probability of breaking a particular encryption.

It is to be noted that quantum computing does not pose a threat to all flavors of cryptographic algorithms. Some algorithm families like asymmetric cryptography (AES, 3DES) are unlikely to be broken. But others like the SHA series, RSA, etc can be easily cracked open.

## What the Future Holds

Quantum Cryptography is the nerd’s answer to the threats posed by the advent of Quantum Computing. We discussed in length in the previous article about how Quantum Computers are the next step towards technological maturity. When compared to “Classical” techniques of computing, Quantum Computers are several orders of magnitude more efficient at specific tasks.

Since Quantum Computing is not generalized, and can only perform tasks efficiently if they are specific, they pose a huge threat to modern security. The Cryptographic encryption practices we know today are highly secure and have been in use for several decades, guarding the gates. But with Quantum Computers, traditional encryptions such as the SHA series, RSA, etc. that have been used for decades could be broken quite trivially.

The World of Blockchain is no less in danger, as all processes that ensure the smooth functioning of a blockchain involve some of the other forms of security.

## Blockchain and its Resistance to Quantum Computing

Blockchains, including the one that bitcoin runs on, make use of extremely advanced encryption which results in permanent, immutable records. The encryption is so strong that there is simply no way anyone using a classical computer can break it.

One such case is the public-private key encryption that most cryptocurrencies use. It’s the private key that would be the primary attack point for any future quantum computer. A Private key is usually a set of alphanumeric code that holds funds for users and permit them to spend. If that is cracked, it becomes easy to get ahold of those funds. The private key performs a function akin to that of password: Every time you use a Bitcoin wallet or send funds from a Bitcoin address.

To save the blockchain from getting attacked by anyone who has a Quantum Computer, one has to develop ways that, firstly do not allow for detection and secondly, are Quantum resistant in the first place.

It is quite evident that bitcoin and other cryptocurrencies and their native blockchains will have to adopt more advanced encryption. “Quantum-proof” blockchains in the future will be a necessity, once Quantum Computers become scalable and cheaper. While the quantum computing threat should not be keeping crypto enthusiasts up at night, it is something worth keeping an eye on in the medium to long term.

## Plan B is ready

Post-quantum cryptography refers to cryptographic algorithms (usually public-key algorithms) that are thought to be secure against an attack by a quantum computer. The need for unbreakable, quantum-resistant encryption is staring us in the face. With the development of quantum computers looming on the horizon, the integrity of encrypted data is at risk now. Fortunately, quantum cryptography, through QKD, offers the solution we need to safeguard our information well into the future – all based on the complex principles of quantum mechanics.

The advancement of quantum computing means that encryption, in general, will have to evolve, and that includes all technologies that make use of encryption, like blockchains. Several projects such as “Quantum Resistant Ledger” (QRL) are being designed by teams working on preemptive solutions to quantum attacks.

*“Quantum computers are unlikely to crack symmetric methods (AES, 3DES, etc.) but are likely to crack public methods, such as ECC and RSA,”* says Bill Buchanan. Bill is a Quantum Clouting expert and a professor in the School of Computing at Edinburgh Napier University in Scotland.

Quantum cryptography is the only known method for transmitting a secret key over a distance that is secure in principle and based on the laws of physics. Current methods for communicating secret keys are all based on unproven mathematical assumptions. These same methods also are at risk of becoming cracked in the future, compromising today’s encrypted transmissions retroactively. This matters very much if you care about long-term security.

## Some Methods of Quantum Resistance

### Longer Encryption Keys

Today’s encryption practices are built on keys that would take classical computers thousands of years to break. This makes attacks extremely improbable. But with a Quantum Computer, they could be easily broken as we saw previously. One of the ways of ensuring resistance could be to make encryption keys longer, into a length that even Quantum computers would not be able to crack. This has several repercussions, such as bigger storage size and need for better processing, but that would be a problem we have to solve if we need to stay safe.

### Avoiding Public Key Detection

A private key gives access to a wallet and allows it to securely store and spend funds. To crack a private key of any particular wallet, once would have to get a hold of the public key and reverse engineer it to get the private key. If we could come out with ways that avoid the detection of public keys and use alternative methods of transferring funds, we cut the problem at its core.

### Symmetric rather than Asymmetric

With symmetric encryption, messages are encrypted and decrypted using the same key. That makes symmetric encryption less suitable for public communication, but significantly harder to break. Symmetric Encryption uses photons of light to verify communication between two parties. This makes them incredibly precise and unfalsifiable, but at the same time expensive and currently non-scalable. This is a hurdle we have to cross, a place to innovate if we need a truly resistant encryption process.

### A Quantum Resistant Hard Fork

A Quantum Resistant Hard Fork is when a blockchain community, having realized that scalable Quantum Computers are on the horizon, collectively decide to hard fork the blockchain. The Hard fork will change the default encryption on the blockchain with newer quantum-resistant ones. These mechanisms will have longer encryption keys, make sure the public keys are hard to detect and cement all the loopholes of the previous system.

Given the advancing of Quantum Computers, we could expect such a wave of Quantum Resistant Hard forks to follow in the coming decade.