What Is Quantum Cryptography, Explained In Simple Terms

Standard encryption won’t survive the quantum age. We need a more secure form of encryption to stand up against the challenge of quantum computers. Thankfully, we have brilliant minds all over the world that are working on the solution. And that solution is Quantum cryptography.

What Is Cryptography?

Here’s an easy way to remember what Cryptography means: “crypt” means hidden, and “-graph” represents writing. Therefore cryptography is hidden (or secure) writing.

If cryptography (or cryptology) is a method of protecting information and securing communications using codes and algorithms, then what is quantum cryptography?

Quantum cryptography is a new, safer means of encryption that uses quantum mechanical properties to carry out cryptographic tasks so information cannot be hacked or intercepted.

The Different Types Of Cryptography

Understanding quantum cryptography is easier when you have knowledge of the different kinds of cryptography that exist. There are three types:

1. Traditional Cryptography
2. Single-key or symmetric-key encryption
3. Public-key or asymmetric-key encryption
4. Quantum Cryptography
5. Traditional Cryptography

This is the form of cryptography that is most commonly used today. By which data encryption is achieved using private and public keys to securely transmit encrypted data.

Single-key or symmetric-key encryption uses a single key to encrypt (or encipher) the data when sent and decrypt (or decipher) the data when received.

Public-key or asymmetric-key encryption uses a pair of keys. A public key is associated with the sender and recipient individually, and a private key is used to decrypt the message.

Let’s look at an example of Public-key encryption:

Alice sends an encrypted message to Bob by looking up his public key in a directory. Bob then uses his private key to decrypt and read the message that he receives from Alice.

The data is encrypted using algorithmic computations that involve the sender’s and the recipient’s private- and public keys, the message itself, and a digital signature that the computation creates.

Quantum Cryptography

Unlike traditional encryption, which involves complex mathematical computation, quantum cryptography utilizes the principles of quantum mechanics to encrypt messages. This makes quantum cryptography much, much more secure, perhaps even unhackable.

Quantum Cryptography Explained

So what is Quantum Cryptography?

Simply put, it is a way to detect an eavesdropper by way of physics. The mathematical complexities allow for confidentiality and authentication of the transmission and ensure that another party cannot intercept the digital data. 

And what is Quantum Encryption?

Essentially this is just another name for quantum cryptography or quantum key distribution. Security systems will need this scientific discipline as quantum computers become more functional. For this very reason, researchers are being encouraged to look ahead to a quantum future. 

How Does Quantum Cryptography Work?

To break down how quantum encryption works, we will provide an example below.

When digital data is sent, photons are transmitted through a filter (or polarizer) which gives the photons one of four possible polarizations and bit designations: 

For example:

The vertical polarization could represent one bit

The horizontal polarization could be a zero bit

45-degree right polarization another one bit

And the 45-degree left polarization also representing a zero bit

Photons will then move to a receiver. There, two beam splitters (horizontal/vertical and diagonal) will read each photon’s polarization. The receiver determines which beam splitter to use for each photon.

Upon sending the stream of photons, the receiver notifies the sender of which beam splitter it used on each photon in the sequence. The sender compares the information with the sequence of polarizations and discards photons read with the wrong splitter. The remaining bit sequence becomes the key.

When a photon is read or copied in any way by an eavesdropper, the state of the photon changes. The endpoints then detect this change. Ultimately the encryption does not allow a photon to be read or copied in any way without detection. 

Why We Need Quantum Cryptography

With quantum key distribution, attacks will be less likely from quantum computers. From financial transactions to confidential communication, the risk of broken encryption is high, and the risks are growing with each day that passes. Companies with critical infrastructures need to secure themselves against quantum computers by implementing quantum cryptographic solutions.

Quantum computing will change the IT landscape in ways that we can’t even imagine.

In past quantum cryptography research, several algorithms are used to solve a variety of problems. This research shows that unauthorized parties can break the existing cryptosystems such as RSA, (EC)DSA, and (EC)DH. 

“This means that quantum computers have the potential to eventually break most secure communications on the planet,” says cryptographer Rafael Misoczki. 

We hope you now know what quantum cryptography is and better understand this fairly complex topic. QC is a very important scientific and security discipline that will shape the future of information technology. 

With quantum cryptography explained, you can get a sense of its impact and why it will be necessary, especially as advances in quantum computing progress.

There will always be a need for confidentiality, integrity, and authenticity in data transmission, and for that, there will always be a need for cryptography.

Quantum cryptography: Public key distribution and coin tossing

When elementary quantum systems, such as polarized photons, are used to transmit digital information, the uncertainty principle gives rise to novel cryptographic phenomena unachievable with traditional transmission media, e.g. a communications channel on which it is impossible in principle to eavesdrop without a high probability of disturbing the transmission in such a way as to be detected. Such a quantum channel can be used in conjunction with ordinary insecure classical channels to distribute random key information between two users with the assurance that it remains unknown to anyone else, even when the users share no secret information initially. We also present a protocol for coin-tossing by exchange of quantum messages, which is secure against traditional kinds of cheating, even by an opponent with unlimited computing power, but ironically can be subverted by use of a still subtler quantum phenomenon, the Einstein-Podolsky-Rosen paradox.