I am looking into TLS 1.3 implementations and am a little confused about what is being referenced in the HKDF functions. Specifically the last argument in the Dervice_Secret
wrapper function. From RFC 8446:
PSK -> = Early Secret
|
+-----> Derive-Secret(., "ext binder" | "res binder", "")
| = binder_key
|
+-----> Derive-Secret(., "c e traffic", ClientHello)
| = client_early_traffic_secret
|
+-----> Derive-Secret(., "e exp master", ClientHello)
| = early_exporter_master_secret
v
In this example ClientHello
is the argument; however, it is unclear what specifics bytes that refers to:
- It is the whole client hello message?
- Is it just a field or extension in the hello message? like ClientHello.random?