14.5 Block ciphers in TLS 1.3
In TLS, block ciphers are used for protecting the confidentiality and integrity of data transmitted over the TLS Record layer. More precisely, a block cipher is used for encrypting TLSInnerPlaintext, the plaintext transmitted by Alice and Bob, into encrypted˙record in TLSCiphertext structure that is, in turn, transmitted over the wire:
Figure 14.15: Encryption at the TLS Record layer
The encryption process is illustrated in Figure 14.15. The fragment field in the TLSPlaintext structure contains the actual payload data. The type field in TLSPlaintext contains the subprotocol type, that is, a numeric value encoding the TLS subprotocol type this data has. The enumeration of valid TLS subprotocol types is shown in Listing 14.1.
The subprotocol type and the actual payload are combined into the TLSInnerPlaintext data structure shown in Listing 14.1. This data is then encrypted using a block cipher into the encrypted˙record field...
