**Encryption** is simply taking some information that makes sense and scrambling it into some mess, so that no one can open it without a specified key. In reality, many websites on the internet contain some of our secret and sensitive information( like credit card info and even messages), to protect these we use Encryption.

So, how do they manage to protect our information?

Well.. The information is first turned into some other sequence or into bits, then we use something called KEY, to protect our information.

This key is like, multiplying every bit of the code with a certain prime number or something else. This makes it difficult to crack. Because, its easy to know the multiplication of two prime numbers. But, its pretty tough to tell the two prime numbers with which the number or the output bit is obtained.

And for encryption, we don’t use small primes, we actually use bigger prime numbers. It may take years to find the factors for that number by a human. But the machine(computer) created by the human is super fast and can find the key faster than you expect, of course that damn tough to do so.

**Now, let’s see what “Quantum Cryptography” is?**

Encryption is done purely based on mathematics. When it comes to highest level of protection, **“Quantum Cryptography”** comes into picture. Unlike encryption, Quantum Cryptography uses physics. In Quantum Cryptography, the information is hidden in Photons(light particles).

The key here is a stream of photons travelling in one direction, with each of these photon particles representing a single bit of data (either a 0 or 1). All of these photons are oscillating (vibrating) in any 360-degree range across any conceivable axis, let the oscillations be grouped into 4 particular states: UP/DOWN, LEFT/RIGHT, UPLEFT/RIGHTDOWN and UPRIGHT/LEFTDOWN.UPRIGHT/LEFTDOWN. The angle of this vibration is known as the polarization of the photon.

A polarizer is that which simplifies a filter that permits certain photons to pass through it with the same oscillation as before and lets others pass through in a changed state of oscillation.

Now, let’s see how a key is made. Let “A” sends oscillating photos may be UP/DOWN, LEFT/RIGHT, UPLEFT/RIGHTDOWN and UPRIGHT/LEFTDOWN. The receiver “B” uses two types of polarizers ( Diagonal and Horizontal/vertical) for each photon, to polarize and ends up with an information waiting for a confirmation by the sender “A” about the polarizer “B” used, that is, Diagonal or Horizontal/vertical polarizer.

Because, a Diagonal polarizer won’t polarize a Horizontally polarized photon, that is, there is a 50% chance of 1 and 50% chance of 0. Finally once the sender “A” confirms the polarizer used for each bit, the wrongly guessed combinations are thrown out and the correct key is obtained.

Using Quantum Cryptography as of now is very tough. This was practically practised in IBM lab.

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