The protocol being used for the exchange.
Will be %NULL if no protocol was specified when creating this object, and either [methodSecretExchange.begin] or [methodSecretExchange.receive] have not been called successfully.
SecretExchange
The protocol being used for the exchange.
Will be %NULL if no protocol was specified when creating this object, and either [method
SecretExchange
.begin] or [methodSecretExchange
.receive] have not been called successfully.