A team of developers created their own CA and started signing certificates for all of their IoT devices. Which action will make the browser accept these certificates?

Setting the private key length to 1024-bit RSA does not affect browser trust decisions and is actually counterproductive, as 1024-bit keys are considered cryptographically weak and may themselves trigger security warnings.

Web browsers maintain a trust store containing root CA certificates from recognized authorities; any certificate signed by a CA in that store is automatically trusted. By preloading the developer-created CA certificate into the browser's or operating system's trusted CA list, all IoT device certificates signed by that CA will pass chain-of-trust validation without triggering browser security warnings.

Enabling HTTPS or port 443 is a transport-layer configuration that does not influence whether the browser trusts the certificate's signing authority; the certificate would still be untrusted without the CA in the trust store.

Switching from SSL to TLS on the IoT devices improves protocol security but does not change how the browser evaluates the certificate's chain of trust; the custom CA must still be in the trusted store for the certificate to be accepted.