All right, let us talk about the metric encryption, although I have told you about symmetric encryption
in one of the previous lectures, but it was just awful.
So what is the symmetric encryption?
Well, from this name, symmetric asymmetric encryption uses the same key to encrypt and decrypt the
message.
So the key that you use to basically generate the plain text to generally decipher text from plain text,
the same key you use to generate the plain text from ciphertext.
So first you generate ciphertext from plaintext, and while decrypting you generate the plain text from
ciphertext.
So basically, symmetric encryption uses a mathematical algorithm, as I said, cryptography is all
about mathematics, it's all about prime numbers, modular arithmetic than a pseudo random numbers,
it's all about mathematics.
So it uses a mathematical algorithm to encrypt and then decrypt the data using a single key.
So what you have to remember when you are asked about symmetric encryption is you have to remember a
single key.
It's a two logarithm, because first you encrypt and then you decrypt.
So first you encrypt, then you decrypt.
That is why it's known as a Dovi algorithm.
It is also referred to as private key encryption or secure key encryption.
Now, why?
It is referred to as private key encryption.
The simple answer here is you have only one key, right?
You have only one key here.
And that key is supposed to be kept private.
As I said, if if you're communicating with the person, that person should also has should also have
the same key.
Because if you're going to unlock a message or unlock a box with one key and if you are using symmetric
encryption, then that person should also have a copy of the same exact same key.
So in that case, if you are traveling or as I as I gave the example of a house and your wife, so those
I give the example in the context of asymmetric encryption because I just wanted you to let me tell
you that if you're unlocking with one key and then you can lock with another key.
But actually that example was off symmetric encryption.
Only the context was different because why?
It is a symmetric encryption.
If you're locking your house with one key, then your wife should also or your wife, your husband should
also have the same copy to unlock the lock.
Right.
So the context, the context was asymmetric encryption.
Now I'm using the same example for asymmetric encryption.
So why does private key?
Because we have seen asymmetric encryption has two types of keys.
Zimet public and private private keys.
The key that you keep to yourself and which you use to encrypt or decrypt the messages and public key
can be of public knowledge.
Anyone can know it.
So do you want the key of your house with everyone?
Do you want everyone to have access to your house?
Well, no.
That is why this key is supposed to be kept private between the communicating parties and hence it is
known as a private key encryption.
Well, again, private and secure are synonymous.
It's also known as a secure key encryption.
So if anyone asks you, hey, please explain me about security encryption, you shouldn't confuse the
security, security, security.
Right.
Symmetric encryption.
So let us have a look at the examples of asymmetric encryption blobfish algorithm to fish algorithm.
Advanced encryption standard data encryption standard reversed Saiful four, five and six versions are
a few examples of symmetric encryption.
Well, one of the drawbacks of asymmetric encryption is a secure sharing of keys.
How are you going to exactly share those keys?
Because even you have to share a key over email.
You have to keep that key confidential.
So again, you have to encrypt that key.
But if you're using asymmetric encryption again and again and again, again, the keys need to be shared.
So secure sharing of keys is a tough problem, but nothing is tough for people who are curious.
So there were two people, Diffie and Helmond together.
They solve this problem and they proposed a new solution to this, which was difficult Hellman key exchange
algorithm in which this key is shared securely without using or without using some other factors.
Well, what is the advantage of symmetric encryption?
You must ask if there are two keys and if that is more secure, why have symmetric encryption in place?
Well, the most fundamental advantage of symmetric encryption is speed.
Symmetric key encryption is much.
Faster than asymmetric encryption, it's it's much faster, although you think that the asymmetric is
much secure, it's not used that much because of its extreme consumption of power, symmetric encryption,
since it uses the same key.
It has a predefined process to do.
That is why the task of encryption and decryption requires, you know, it's a speedy task.
Less time is required in order to carry out the entire process.
So drawback is secure sharing of keys.
But again, there were two brilliant people out there, Diffie and Helman, who proposed the development
algorithm.
So to sum up what you have to remember when it comes to symmetric encryption is the same keys used.
OK, I'll just mark it again.
So same keys used, mathematical algorithm, single key to be private, key encryption.
And these are a few examples.
And again, you have to remember, as for speed, as for symmetric encryption, the only drawback is,
again, as that is secure sharing of keys.
In the next lecture, we'll talk about a few examples of asymmetric encryption will see different algorithms,
the key size.
What is the key size for those algorithms?
What is the input and what is the exact output?
OK, I have I have got this question a couple of times, what is the input?
Well, you cannot give a word document at random, right?
That is fixed input size for each of different algorithms and inline that algorithms.
The data is encrypted.
You cannot give 2000 characters to encrypt, uh, as a single block.
So there are different various block sizes in case of symmetric encryption, which we will be seeing
in the next lecture.
All right.
Keep the momentum going.
You're doing a great job.
If you have any questions, do let us know and I'll be happy to solve them for you.