Update dispatcher readme

dispatcher/README.md

@@ -4,12 +4,13 @@ The dispatcher simplifies the communication between the horcruxes.
 It should be deployed on a machine that is reachable by every participating horcrux.
 The dispatcher transmits secret shares between horcruxes.
 All the messages are encrypted with the RSA public key of the recipient, so there is no way for a dispatcher to access the secret data.
+In order for the participants to interact with the dispatcher, they must provide `AUTHENTICATION_KEY`.
 
 # Local setup
 
 Run the following command from the home directory to start the dispatcher locally:
 ```shell script
-DATABASE_PATH=sqlite:///./dispatcher.db uvicorn dispatcher.main:app --reload
+AUTHENTICATION_KEY=securekey DATABASE_PATH=sqlite:///./dispatcher.db uvicorn dispatcher.main:app --reload
 ```
 
 # Remote access
@@ -19,7 +20,7 @@ to allow other horcruxes to connect to your locally running dispatcher.
 
 Run the following command in first terminal window:
 ```shell script
-DATABASE_PATH=sqlite:///./dispatcher.db uvicorn dispatcher.main:app --reload
+AUTHENTICATION_KEY=securekey DATABASE_PATH=sqlite:///./dispatcher.db uvicorn dispatcher.main:app --reload
 ```
 
 Run the following command in second terminal window: