Now we're going to see an interesting protocol that is a pretty good privacy, as the name suggests,
an excellent protocol, and the walking is very simple to understand.
If you have understood the previous cryptography and the public key encryption decryption videos, then
this lecture is going to be a wonderful lecture for you.
Now, in this lecture, I am not going to have any bullet points.
I'm just going to explain through the slides.
So in the early 1990s, Phil Zimmermann, also from M.I.T., that is Massachusetts Institute of Technology
and US, wrote most of the code for his freely available version of public key encryption designed to
encrypt data for email transmission.
PGP is mostly used for email transmission.
Make sure you remember that Zimmerman basically compared email to postcards because anyone can read
e-mail messages traversing the Internet just as they can.
Postcards traveling to the Postal Service.
Right by contrasting, he compared an encrypted message to a letter mailed inside an envelope.
And this is the figure of PGP encryption system.
So don't worry.
I'm going to explain what exactly is now in the figure or you can see on the screen.
Let me take my pen.
Yes.
So the document this is the original document.
OK, now the document is encrypted with a session key.
So let's consider this is a session key, OK, which is then encrypted with the public key of the recipient.
So let's see.
Here is the recipient and his public key is available in this key store because public is a public knowledge.
It is available to everyone.
Now with this public key.
This key is encrypted because we know that whenever you want to send a data over the Internet in order
for the recipient to decrypt the data with his private key, you must encrypt the data with the public
key and then only the public or the private can decrypted.
OK, so now this session is encrypted with the public key of the recipient and this data is also encrypted
with the session key.
And then the encrypted document, along with the encrypted session key with the help of public key is
sent over to the recipient here.
OK, I'll erase it so that you will have a clear picture of.
Oh, yes.
Now, let's see how do we explain the decryption process?
So once again, I will revise the encryption process, you have the document, you have a session with
the help of session key, you encrypt that document and then you end this session with the help of the
public and then this encrypted document, plus encrypted session key.
You sent it over to the recipient here.
Now, when the recipient receives the encrypted document along with the encrypted session key, now,
since this session key is encrypted with the public key of this recipient, it can be easily decrypted
with the help of private keys of the recipient.
So when the recipient decrypt the encrypted key with his private key, he gets the original session
key.
He gets the audience session key.
And with the help of this session key, he then decrypt this document to form the new document to get
the original document.
So in this case, what you have to remember is session key encryption is done using symmetric encryption.
That is the same key for encryption and the same key for decryption.
But in order to transfer the session key over the Internet, automatic encryption is used.
Now, automatic encryption takes a longer time than symmetric encryption.
That is why in order to just transfer the keys, asymmetric encryption is used in most of the today's
world.
But when it comes to encrypting local documents or the symmetric key, encryption is used.
So make sure you remember this is the example of pretty good privacy.
OK.
Now, since the recipient is the only person with the matching private key on the deck and decrypted
session, because there we are using asymmetric key, uh, encryption, uh, for the personal use only.
And the name implies it's really pretty good privacy.
RNC data security that is reversed.
Shamir and Adelman security and the US federal government both had a problem with Zimmermann's product.
Now, the RNC complained about patent infringement and the government actually decided to prosecute
Zimmerman for exporting munitions, great software.
But the government actually dropped the charges against Zimmerman and the licensing fee is paid to Oddisee.
So today, BGB and other public utility products are readily available.
But if you cleverly see this is the most of it actually is a good protocol for encryption and preventing
your data over the direct transfer.
I hope my lectures are very clear to you because I'm trying to explain all those things in very simple
and clear words.
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I will see you in the next lecture.