Returns a function that resolves to a key object downloaded from a remote endpoint returning a JSON Web Key Set, that is, for example, an OAuth 2.0 or OIDC jwks_uri. The JSON Web Key Set is fetched when no key matches the selection process but only as frequently as the cooldownDuration option allows to prevent abuse.

It uses the "alg" (JWS Algorithm) Header Parameter to determine the right JWK "kty" (Key Type), then proceeds to match the JWK "kid" (Key ID) with one found in the JWS Header Parameters (if there is one) while also respecting the JWK "use" (Public Key Use) and JWK "key_ops" (Key Operations) Parameters (if they are present on the JWK).

Only a single public key must match the selection process. As shown in the example below when multiple keys get matched it is possible to opt-in to iterate over the matched keys and attempt verification in an iterative manner.