Symmetric Encryption and Data Transfer

With session keys established, the handshake concludes with both parties sending a "finished" message, encrypted with the newly established session keys. This serves as a final verification that the handshake completed successfully and both parties have the correct keys. From this point forward, all application data is encrypted using symmetric encryption algorithms like AES (Advanced Encryption Standard).

Symmetric encryption operates on blocks or streams of data, transforming plaintext into ciphertext using the session key. Modern cipher suites typically use AES with 128-bit or 256-bit keys, providing security that would take centuries to break with current computing technology. The encryption process includes not just scrambling the data but also adding message authentication codes (MACs) or using authenticated encryption modes that ensure data integrity.

Each encrypted record includes mechanisms to prevent replay attacks, where an attacker might capture and retransmit encrypted data. Sequence numbers, included in the MAC calculation but not transmitted, ensure that records arrive in the correct order and haven't been duplicated or removed. This attention to detail in the protocol design addresses various attack vectors that might otherwise compromise secure communications.