Quantum computers are the next generation of computers humanity is currently developing. They promise fast computing, better and more precise simulations of quantum and macro physics and much more. But having this kind of “godly” power comes with its own price. We are going to focus on the threat posed by quantum computers for general, everyday internet and IT security.

**First of all, what is a quantum computer??**

Quantum computer is a computer which uses quantum physics and phenomenon to perform computation.

A traditional computer uses a regular transistor which is 14 nano meters big. For context, the red blood cell in our body is 500 times bigger than a transistor. As transistors are shrinking day by day to the size of few atoms, quantum physics comes into play.

Unlike traditional computers which use bits – a single state such as “on, off” or “0, 1” to perform calculations, quantum computers use qubits. A qubit can be any two level quantum system such as the spin of an electron or a single photon. 0 and 1 are the system’s possible states. While traditional computers assign one of the two states (0 or 1) to a bit, a quantum computer assigns both the values to a qubit (both 0 and 1). Thus the qubit is in a quantum state called superposition which roughly means, that the qubit can be either 0 or 1 at the same time and when we test the qubit for its value, it collapses into either one of them. Hence, we can’t predict the exact value of a qubit until it is tested.

Calculations using qubits are much faster than bits. A bit can be one of two possible values – 0 or 1. But a qubit can be both the values at the same time. When we increase the number of bits, say for example to 4, we can have 1 of 24 possible values at that instant. But when we are working with qubits we can have all of the 24 possible values at that instant itself. This quality of quantum computers increases their computing capacity exponentially for each qubits added.

These qubits are then connected by a phenomenon named quantum entanglement. Simply put, quantum entanglement connects two quantum objects through some common link such as their respective spins. Due to this, we can know the value of one of the linked object just by knowing the value of the other and not by testing it. For example, we know the two electrons present in a Helium atom have opposite spins. If we separate them from the atom, they would still be linked by the fact that they both have opposite spins and with that we can know the value of one electron just by knowing the value of the other irrespective of the distance between them.

Careful and smart exploitation of quantum entanglement and superposition can result in a computer which is much more powerful than our traditional ones.

### **Wait how is this a threat for our digital security?**

Saying that cybersecurity uses cryptography is an understatement. We encrypt our data with complex mathematical concepts and exchange the keys to decrypt these data or vice versa. But quantum computing has the power to break this whole system. To know why, we should first know what cryptography is.

**Cryptography**

Cryptography has been with us since the days of Julius Caesar (Caesar Cipher). It was a simple yet effective means of secure transportation of information if the third party didn’t know how to decrypt it. But we have come a long way since then. Today’s computers can decrypt old encryption methods like Caesar Cipher within minutes, if not within seconds. To account for this, we have come up with more sophisticated methods to encrypt our data. We use complex mathematics like prime factorization and other concepts to encrypt the data. To decrypt these encrypted data, one has to have the “key” to the encryption. Otherwise, they have to brute force it by trying every possible answer/key. Brute forcing an encryption which has a sufficiently strong key/password (long, uses numbers, alphabets and symbols) is a very computationally expensive process. Due to the limitations of traditional computers in terms of computing power, cracking a strong key/password might take years if not centuries. Its not impossible to crack these keys, but the time required to do that is so big that it is not worth the try.

This is the backbone of modern cryptography. Create an encryption method which is virtually impossible (meaning, it take a very long time) to crack without the key.
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**How quantum computers come into this??**

The main idea behind modern cryptography as said earlier is to create an encryption which takes very long to crack with our traditional computers. But when we include quantum computers into the scene, it changes everything. Quantum computers are exponentially powerful and faster than our traditional computer. This means that they can break cryptographic keys by quickly calculating the secret keys.

A task which was previously considered infeasible and took years to finish is now easy and is done within considerably very less time. This means that if someone has a quantum computer, they basically can see everything, everyone sends. Banking details, user information for websites and some sketchy websites you visit when no one is at home. This is a serious breach of privacy and even more, the world’s banking details, credit and debit card credentials and everything related to e-banking are at stake.

**But it’s not quite there, yet. **

The dangers posed by the arrival of quantum computers is huge. But the technology is not quite there yet. Yes, we have quantum computers right now, but their computing capacity very less and do not pose a threat to anyone.

The quantum computers we
have now are really like the old computers made in post WWII. They have
many limitations. They are big, expensive and are not that powerful. You
can buy one right now at D-Wave for $10 Million, but it would be highly
impractical unless you are Google or IBM or some other big agency or
government. Current quantum computers use superconducting flux loop
technology which requires temperatures near 0 Kelvin which is not
possible for the average consumer.

In the next decade or two, it is expected that most big companies and governments will have these quantum computers. So the threat is still there but we have enough time to tackle it.
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**Defense against quantum computers**

For long, we have based the concept of cryptography on the computational power of our computers. With the rise of quantum computers, we can’t do that and we need to fundamentally rethink how we see cryptography.

Cryptographers and cybersecurity experts have already started to work towards that problem. Post-Quantum cryptographic methods like Lattice-based algorithms and Quantum-key distribution are some promising solutions but they are far from being perfect.
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**Final thoughts**

The development of quantum computers is inevitable. I see them as the next big thing for humanity. Quantum computers provide us with many benefits. They give more computational power which can be used in all sorts of fields from quantum simulations to spaceships. But they also pose a threat to our digital security. So we should develop a fool-proof solution to this threat before it even arises.

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