Update draft-ietf-rats-reference-interaction-models.md

Co-authored-by: Thomas Fossati <thomas.fossati@linaro.org>

Author: henkbirkholz

draft-ietf-rats-reference-interaction-models.md

@@ -229,7 +229,7 @@ In order to ensure Evidence is appropriately conveyed through the interaction mo
 
 Authentication Secret:
 
-: An Authentication Secret MUST be established before any RATS interaction takes place and be exclusively available to an Attesting Environment of the Attester.
+: An Authentication Secret MUST be established before any RATS interaction takes place, and it must be made available exclusively to an Attesting Environment of the Attester.
 
 : The Attester MUST protect Claims with this Authentication Secret to prove the authenticity of the Claims included in Evidence.
 The Authentication Secret MUST be established before RATS take place.