+* -tls_key/-tls_cert: enable TLS and specify key and certificate file
+* -passwords: enable client authentication and specify path to
+ passwords file
+* -verbose: increase log messages verbosity
+
+AUTHENTICATION
+
+You can turn on optional client authentication by preparing passwords
+file and using the -passwords argument. Format of passwords file is:
+
+ login1:password1\n
+ login2:password2\n
+ …
+
+You can force rereading of passwords file without server interruption by
+sending HUP signal to him.