Authentication in cassandra binary protocol v2

[Mathieu D'Amours]

Hello,

I stumbled upon this description in the binary protocol specs [4.2.7. 
AUTH_CHALLENGE]:

> The body of this message is a single [bytes] token. The details of what this
> token contains (and when it can be null/empty, if ever) depends on the actual
> authenticator used.


I looked in C* builtin authenticator classes, `AllAllowAuthenticator` and 
`PasswordAuthenticator`, but couldn't find this sort of 
information. Could someone point me in the right direction? 

Thanks in advance,

Mathieu