[lacker]

Even now we've adopted encryption, which appears sufficiently random.

When you pick up an encrypted signal, it's still obvious there's a signal there. Radio telescopes will pick up cell phone signals, for example; that's why there is a radio quiet zone near the Green Bank telescope. You just can't decode the message itself without the encryption keys and algorithm.

[CamperBob2]

As long as it's over the thermal floor within its own bandwidth, yes, it will be obvious that there's still a signal there.

When it comes to interplanetary reception, though, any intelligently-constructed signals will likely be below the noise floor unless deliberately broadcast for our benefit. No coherent carrier or sidebands? No spreading sequence? No chance of detection, whether encrypted or not.