SSL/TLS

SSL (Secure Sockets Layer) and its successor, TLS (Transport Layer Security), are cryptographic protocols designed to provide secure communication over a computer network. They are the backbone of HTTPS, the secure version of the web protocol. When you see a padlock icon in your browser's address bar, it means an SSL/TLS connection is active. The primary goal of SSL/TLS is to ensure the confidentiality and integrity of data exchanged between a user's browser and a website's server, as well as to authenticate the server. This is accomplished through a process called the TLS handshake. The handshake brings together all the cryptographic concepts we've discussed. Here’s a simplified overview: 1. The client (your browser) connects to the server and requests a secure session. 2. The server responds with its SSL certificate. This certificate contains the server's public key and is digitally signed by a trusted Certificate Authority (CA), which verifies the server's identity. 3. The client verifies the server's certificate with the CA. This step uses the CA's public key to verify the signature, ensuring the certificate is legitimate (asymmetric cryptography and digital signatures). 4. The client generates a new symmetric key (called a session key) for this specific session. It then encrypts this session key using the server's public key (asymmetric encryption). 5. The server decrypts the session key using its private key. Now, both the client and the server have the same secret session key. 6. All subsequent communication for the rest of the session is encrypted and decrypted using this fast, symmetric session key. This hybrid approach leverages the best of both worlds: the security of asymmetric cryptography for key exchange and the speed of symmetric cryptography for bulk data encryption.