Encryption is the process of taking a message

and scrambling it’s contents so that only

certain people can look at your message.

There are two types of encryption: symmetric

and asymmetric encryption.

Let’s first take a look at symmetric encryption

to understand why asymmetric encryption was

created.

To do that, let me introduce you to Alice

and Bob.

Alice has a sensitive document that she wants

to share with Bob.

She uses an encryption program to protect

her document with a password or passphrase

that she chooses.

She then sends the encrypted document to Bob.

However, Bob cannot open this message because

he doesn’t know the passphrase that Alice

used to encrypt the document.

In other words: he doesn’t have the key to

open the lock.

Now comes a real problem: how does Alice share

this passphrase securely with Bob?

Sending it through email is risky because

others might find the passphrase and use it

to decrypt any messages between Alice and

Bob.

This is exactly the kind of problem that asymmetric

encryption intends to solve.

It’s compareable to a mailbox on the street.

The mailbox is exposed to anyone who knows

its location.

We can say that the location of the mailbox

is completely public.

Anyone who knows the address can go to the

mailbox and drop in a letter.

However, only the owner of the mailbox has

a key to open it up and read the messages.

Let’s go back to technical details.

When using asymmetric encryption, both Alice

and Bob have to generate a keypair on their

computers.

A popular and secure way for doing this is

by using the RSA algorithm.

This algorithm will generate a public and

private key that are mathematically linked

to each other.

Public keys can be used to encrypt data and

only the matching private key can be used

to decrypt it.

Even though the keys are linked together they

cannot be derrived from each other.

In other words: if you know someone’s public

key, you cannot derrive his private key.

If we retake our mailbox example then the

mailbox’s address would be the public key

something that everyone is allowed to know.

The owner of the mailbox is the only one who

has the private key and that is needed to

open up the mailbox.

Let’s now take a look at how Alice and Bob

can use asymmetric encryption to communicate

securely with each other.

They start by exchanging their public keys.

Bob gives his public key to Alice and Alice

gives her public key to Bob.

Now Alice can send her sensitive document

again.

She takes the document and encrypts it with

Bob’s public key.

She then sends the file to Bob, who uses his

private key to unlock the document and read

it.

Because they use asymmetric encryption, only

Bob is able to decrypt the message.

Not even Alice can decrypt it because she

doesn’t have Bob’s private key.

The strength and security of the asymmetric

encryption now relies on Alice and Bob to

keep their private keys well protected.

If an attacker steals Alice’s private key,

it can be used to decrypt all messages that

are intended for Alice.

However, the attacker cannot decrypt messages

that where sent by Alice because that requires

Bob’s private key.

Asymmetric encryption is used in a lot of

places where security really matters.

You might not be aware of it, but everytime

you visit a secure website via HTTPS, you’re

actually using asymmetric encryption.

It’s also being used to securily send emails

with the PGP protocol.

And one last example: Bitcoin also uses asymmetric

encryption to make sure that only the owner

of a money wallet can withdraw or transfer

money from it.

So now you know how asymmetric encryption

works and what the differences are between

asymmetric and symetric encryption.

If you liked this video, consider supporting

me by sharing it and subscribing to my YouTube

channel and as always: thank you very much

for watching!

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