"Applications of Asymmetric Public Key
Cryptography"
This video requires concept from the "Cryptography" video uploaded earlier. Click on the card or link in the
description to watch the video on "Cryptography" first.
Basically, public key cryptography is used to authenticate or encrypt.
Starting with authentication, which is used in digital signatures.
Alice is the CEO and she wants to exchange information with employees of the company.
She will generate a private-public key pair.
This is a one-time process and the new key pairs are only generated if the private key is lost or leaked.
She will keep her private key secret and share the public key with all the employees say Bob1, Bob2, Bob3 & so on
Alice will use her private key to encrypt the message and send it to all the employees.
The employees will use Alice's public key to decrypt the message.
The fact that Alice's public key is able to decrypt the message implies that
the message must have been encrypted using Alice's private key.
As only Alice has access to her private key means the message is definitely sent by Alice.
Therefore, it provides authenticity of the source of the message but the messages are visible to
everyone who has the public key. Every
message can be read by all the employees
and there is no way to send a message to
just one employee.
Another use of public key cryptography
is to use encryption.
To communicate securely, every employee of the company will have to generate their own
private-public key pair and exchange their
public keys.
Alice wants to send a message to an
employee named Bob. She uses Bob's public
key to encrypt the message. The message
encrypted by the public key can only be
decrypted by the corresponding private
key which is with Bob.
Similarly, Bob can reply using Alice's
public key to encrypt the message which
can be retrieved only by Alice's private key.
Thus, both sides can have encrypted communication
but the authenticity of the source of
the message is missing. There is no way
to be sure who sent the message.
As everyone has access to each other's
public key.
For most of the applications, both authentication and encryption is required at the same time which is
implemented using more complicated
algorithms.
Don't forget to go back and finish watching the cryptography video.
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Thanks for watching
