Public key encryption. What is a key?

Question

Cryptography

Hello
, I think you all know what public key encryption is, there is no point in explaining.
So what is a key?
Is it an encryption program?
Or what is it?

Answer 1

I'll just leave this here.

Answer 2

This asymmetric encryption system is called public key cryptography.
This system works like this:
A random closed (private) key is generated (recall that a key or cipher is a sequence of characters) and, according to a certain algorithm, another public (public) key is selected for it. At the same time, for any private key, there is only one version of the public key. Those. these keys (private and public) always work in pairs (bundle).
Further, the received open (public) key is sent via any open communication channels to the sender of the secret message.
Having received the public (public) key, the sender uses it to encrypt the message and sends it to the recipient who has the corresponding private (private) key.
The recipient decrypts the secret message using his private (private) key pair with the public (public) key that was used to encrypt the message.
It should be noted that an open (public) key can only encrypt a message, but it will not be possible to decrypt it with this key. For decryption, only the private (private) key from the pair is needed. This is how the asymmetric encryption algorithm works.
https://www.intuit.ru/studies/courses/28/28/lectur...
https://intsystem.org/security/asymmetric-encrypti...

Answer 3

Googling about asymmetric encryption. There just different keys are used for encoding and decoding. There and about the key will be.

Answer 4

Excellent visualization of the principle of asymmetric encryption https://www.youtube.com/watch?v=vFjq9pID4-E

Answer 5

You can only exchange data securely with someone if both of you have a common key to encrypt and decrypt it that no one else knows about. The problem is how to get both of you to have it without anyone knowing. Those. how to transfer the key over an open channel without compromising it. Asymmetric encryption is just about that.
The algorithm of this operation is as follows:
1. The server sends the public key to the client over an insecure connection.
2. Based on the public key of the server, the client creates a shared (common) key and stores it with himself.
3. The client encrypts its shared key and sends it encrypted to the server.
4. The server decrypts the encrypted shared key using its private key and receives the shared key from itself.
Asymmetric encryption completed its task - handshake took place. Further, the client and server, having a shared key, can exchange already symmetrically encrypted data.