Does AWS Cognito relying party support encrypted responses?

[shibboleth655 at lewenberg.com]

We have someone who wants to set up an AWS Cognito for user 
authentication with our IdP as the authentication source.

I have looked and while AWS's documentation does not explicitly say that 
Cognito acting as a relying party does not support encrypted responses, 
I can see nowhere anything about provisioning a certificate to give to 
the IdP.

Has anyone setup AWS Cognito as a relying party? If so, were they able 
to send encrypted responses?

Adam L.