How is it possible that people observing an HTTPS conne...
Câu trả lời How is it possible that people observing an HTTPS conne...
When an HTTPS connection is established, the encryption mechanisms in place ensure that even if someone is observing the connection, they cannot decrypt the data being transmitted. This security is achieved through a combination of asymmetric and symmetric encryption, facilitated by the Transport Layer Security (TLS) protocol. Here’s a detailed explanation of how this works:
1. TLS Handshake and Asymmetric Encryption
The process begins with the TLS handshake, which involves the following steps:
Client Hello: The client (e.g., a web browser) sends a "Client Hello" message to the server. This message includes information about the supported encryption algorithms (cipher suites) and the latest TLS version the client can support[3][4][8].
Server Hello: The server responds with a "Server Hello" message, selecting the encryption algorithm and TLS version to be used. The server also sends its SSL/TLS certificate, which contains its public key[3][4][8].
Certificate Verification: The client verifies the server’s certificate against a trusted Certificate Authority (CA). This step ensures that the client is communicating with the legitimate server and not an imposter[3][4][8].
Key Exchange: The client generates a session key (a symmetric key) and encrypts it using the server’s public key. This encrypted session key is then sent to the server[3][4][8].
Session Key Decryption: The server decrypts the session key using its private key. Now, both the client and the server have the same session key, which will be used for symmetric encryption of the data transmitted during the session[3][4][8].
2. Symmetric Encryption for Data Transmission
Once the session key is established, all subsequent data transmitted between the client and the server is encrypted using symmetric encryption. Symmetric encryption is chosen for data transmission because it is faster and more efficient than asymmetric encryption[3][4][8].
3. Why Observers Cannot Decrypt the Data
Several factors ensure that observers cannot decrypt the data:
Asymmetric Encryption Security: The initial key exchange uses asymmetric encryption, where the public key is used to encrypt the session key, and only the corresponding private key can decrypt it. Observers do not have access to the server’s private key, so they cannot decrypt the session key[3][4][8].
Symmetric Encryption Security: Once the session key is established, symmetric encryption is used for...
