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

@@ -202,7 +202,7 @@ Similarly, deviations from the generic model described in this document can be i
 In order to ensure appropriate conveyance of Evidence, the following requirements MUST be fulfilled:
 
 Integrity:
-: Information provided by an Attester MUST NOT have been altered since it was created. This may be achieved through by symmetric signature, e.g., PSA TF-M profile, or asymmetric, like ECDSA.
+: Information provided by an Attester MUST NOT have been altered since it was created. This may be achieved via symmetric cryptography, e.g., using COSE Mac0 as in PSA TF-M profile ({{Section 5.2 of I-D.tschofenig-rats-psa-token}}), or asymmetric, like ECDSA.
 
 Authentication:
 : The information provided by the Attester MUST be authentic. To do this, the Attester should authenticate itself to the Verifier. This can be done through implicit authentication using a digital signature over the Attestation Evidence, which does not require additional protocol steps, or by using a secure channel including authentication.