public Optional<String> getSigningKey(final RegisteredService registeredService) {
        val property = getSigningKeyRegisteredServiceProperty();
        if (property.isAssignedTo(registeredService)) {
            val signingKey = property.getPropertyValue(registeredService).value();
            return Optional.of(signingKey);
        }
        return Optional.empty();
    }
Gets signing key.

@param registeredService the registered service
@return the signing key
support/cas-server-support-token-core-api/src/main/java/org/apereo/cas/token/cipher/RegisteredServiceJwtTicketCipherExecutor.java