# Quantum Cryptography

Let’s begin by playing two truths and a lie...

**Number 1:-** Remember Christopher, the Enigma codebreaking machine from ‘The imitation game’? What if I were
to tell you that we are not that farfetched from such technology that can
literally crack ANY code?

 The current encryption, on a laymen level, can be understood as a
naïve lock and key setup that we use. Let's suppose you're the pizza guy:
angels in uniforms, one reason - one word - pizza. Let's suppose I want
to make a secret special pizza order to you (the reader). I can’t simply
send it to you as there’s this one friend of mine who is crazy for pizza
and can easily see or manipulate the message by adding his weird
toppings. And so, I need to send it to you in some scrambled form. And
here comes the role of the lock. The special lock that we have can
scramble the information into some unreadable form and the reader i.e.
you must have the key to unscramble that message and hence read it.

 Analogous to the real-life scenario the key intended for a particular
lock can only unlock its respective lock. The communication between you and me can be thought of as us standing apart at the end of a tunnel
and the eavesdropper lies somewhere in the middle, spying in the dark. I
cannot directly send you the key as the eavesdropper can also have the
same copy of the key and hence, he then will also be able to unscramble
all of the messages. So what we tend to do is make a PUBLIC lock that
is distributed to everyone (and so DOES the eavesdropper) The sole
task of the public lock is to encode messages, (and it cannot decode any
of the messages) only the receiver i.e., you should have the Super-Secret
key to this public lock and hence will be used to unlock the messages to
be communicated.

**Case 1:** If I want to send you a message:

Easy, I’ll use my Public lock and scramble the message and send it to
you through the channel as assuming only you are the one in the whole
world with the key hence only you will be able to unscramble the
message.

Even if the eavesdropper gets a copy of your scrambled message, he can
do nothing as

1). The obvious one he does not have the key.

2). Second the public lock that was publicly distributed can be used
ONLY to scramble and not unscramble the messages.

**Case 2:** What if you want to send me a message?

Currently, even if sender sends you messages, you won’t be able to
unscramble any messages as you just have the public lock.... that can
unscramble information

So, I now need to come up with something...

So, I make my own little shiny private key that I will use to scramble
and unscramble messages and I make sure to scramble the copy of this key by using the Public lock before sending it to you. Once you have
my scrambled key, you can use your Super-Secret key to unscramble it
and guess what? We’ve established a secure connection!

**Case 3:** What if the
eavesdropper cracks i.e
guesses the key to the
public lock?
Problem: As we are
freely distributing the
public lock over the
channel, hence, the
eavesdropper can easily
get a copy of the key to
this public lock.
Practically it would take
him a lot of time to go
through all the possible
sets of public key
combinations. But it’s
possible; I’d say
‘Beware’ if you feel
you’re astronomically
unlucky

**Solution:** We will keep
on changing the keys that I
sent you (in the second
case), so even if he finds
out the key, he won’t be
able to access anything
later on. It’s too late already.... that the message has been well received. The pizza box would
already be empty and ‘my precious’, I meant ‘my pizza’ would be all
mine by the time he finds it (which he really won’t).


MISSION ACCOMPLISHED.


![WhatsApp Image 2021-03-21 at 7.53.32 PM.jpeg](https://cdn.hashnode.com/res/hashnode/image/upload/v1616337903208/yvt-zmjHr.jpeg)
Figure i - It isn’t some crazy rich
chandelier in a crazy rich palace, this is
the very quantum computer we are
talking about. The qubits are stored at
very low temperatures as in -460 degrees
Fahrenheit and hence arises the need of
huge cooling structures.

 Don’t be shy you can surely give yourself a good pat for this because
you know the basics of the working of the keys and locks are nothing
but functions that convert the given message into an encoded or
encrypted form that is not readable without changing it back to the
original message.

 These keys are basically nothing but large sequences of 1’s and 0’s
made up of 32 bits or characters. Hence, if the eavesdropper wants to
guess the key value then he has to go through 232 (around 4294967296)
combinations until he finds the key. It clearly is a very tedious task and
hence makes it safer and safer unless you are astronomically unlucky
but......Quantum Computers! With the help of the Quantum Computer,
this process of going through all the 4294967296 combinations can be
done in polynomial time and hence your key can easily be guessed by
the eavesdropper! But don’t worry the advent of the quantum computing
is a double-edged sword, we can use quantum to fight back quantum!
 To summarize I have a personal lock and a personal key pair and
also a public lock that has been distributed to everyone. The main trick
is that I first use my personal lock to scramble and transmit all the
messages, but in order to unscramble the messages the receiver must
have my personal key, so now I make use of the public lock and
scramble my public key itself and send it as the part of the information
that is to be sent.

 So that the sender also has the personal key and he and only he will
be able to unscramble the messages.

**Number 2:-** The era will now be where we will see people saying
“Distance is just a number”. The term teleportation is no longer just a
vague idea that remains a figment of imagination in the mind of a seven year-old or something that the creators of the Star Trek series were not
aware of back then.

 The concept of entanglement prevails in the quantum realm where
two bits (quantum bits) are made to point to the same state and change
in either one of the qubits Imagine two qubits, one in India and one in
Canada. Let the Canadian qubit stand for ‘C’, and the Indian qubit ‘I’.
When qubit ‘C’ is measured as being a ‘1’, then qubit “C” in Canada
instantaneously collapses in correspondence with how the qubits were
put into entanglement i.e. you can predict its behavior I.e. a ‘1’ or a ‘0’.


![WhatsApp Image 2021-03-21 at 7.53.32 PM (1).jpeg](https://cdn.hashnode.com/res/hashnode/image/upload/v1616337862543/7FgUfpTQQ.jpeg)

 This is true no matter how far away the qubits are. This is literal
teleportation of the bits; you may argue that in the present state too can
be instant communication, but the current instant communication is the
result of the high and efficient underlying computer network
architecture, without this, there cannot be any sort of communication.

 To be honest this is sad teleportation because literal teleportation
involves sending you to some other place (Starbucks from home huh?), which is a better way of saying that firstly all your particles are
destroyed at one end, which is a sugar-coated way of saying “You die”
and those particles are then used to create the new you at the other end
(The Resurrection stone?) that just thinks “It’s you again”. Sounds
fancy isn’t it!
 
This is kind of obvious because you cannot have two of ‘yous’ in the
same world. That’d be so cool but yeah not possible! But when we look
closely quantum teleportation does teleport or rather send the
information about the state of the qubits with ease. And that’s all we
need...you are made up of matter, matter has atoms, atoms have
electrons and if somehow, we can teleport all this information of ‘you’
being ‘you’ at
the atomic
level, we can
recreate a new
‘you’. That's
just a way of
bringing in a
picture of
what it
actually is.
 You must
be thinking
what about the
clone left on
the other end?
 

![WhatsApp Image 2021-03-21 at 7.53.32 PM (2).jpeg](https://cdn.hashnode.com/res/hashnode/image/upload/v1616337848532/OCBMYOYV7.jpeg)

***Quantum
mechanics to
the rescue:*** Quantum mechanics has this theorem known as the nocloning theorem which states that” It is impossible to create an identical
copy of an arbitrary unknown quantum state.”(In this example the
information of atoms of ‘you’)

Number 3:- Your Spicy Italian sub fell down the road, crushed by a
car! Not a problem (reviving sounds of the time machine turning on...)
give me a sec and I'll be back in no time with your sub...

.

.

BUMMER ALERT

.

.


![WhatsApp Image 2021-03-21 at 7.53.32 PM (3).jpeg](https://cdn.hashnode.com/res/hashnode/image/upload/v1616337829191/D9VzmD7WXJ.jpeg)

In the end, I would just say thoughts and prayers for that sub…
Don’t tell me you believed the time machine thing! You should be sure
that we can never build a time machine. Let's assume we build a time
machine in the future. The very first thing that I can come up with to do
with the time machine is to go back to the past and give the time
machine to myself so that I never have to actually make it!

Hence, we all collectively conclude that the Number 3 is a lie and the
other two are truths.


![WhatsApp Image 2021-03-21 at 7.53.32 PM (4).jpeg](https://cdn.hashnode.com/res/hashnode/image/upload/v1616337818700/X-bo-Ese4.jpeg)

Quantum
computing’s
purpose is to aid
and extend the
abilities of classical
computing.
Quantum computers
will perform certain
tasks much more
efficiently than
classical computers,
opening for a wide
area of application,
providing us with a
new tool for
specific applications.
This isn't some revolt
but is surely an uprising. Quantum computers will not replace their
classical counterparts. In fact, quantum computers require classical
computers to support their specialized abilities. But we have a lot of
waiting to do before we see quantum computers in our laps and labs.