Humans and the Cheela work out a pact so the Cheela work as a computer for the humans.
Got a problem? Send it to the Cheela. They'll design your home, work out a complex math problem or tackle any mundane thinking job. Even if no one really wants to work on your problem, in the space of a human day generations of Cheela come and go and someone will pick it up and have a go in their spare time. They'll post it to their internet and some Cheela geek with nothing better to do will give it a shot.- Of course if your original request gets misplaced by the time you ask about it a week later, millennia will have passed by...
Humanity is handed the encryption codes before long.
It was just a bunch of Cheela in power who decided to force the humans to work for stuff. Give the Cheela two hours and the political clime will change or some radical-human-loving fringe group will send it to us. Humans will not wait to discover faster-than-light travel.
The key the cheela sent them to encrypt the instructions on how to travel faster than light was placed in orbit around Epsilon Eridani, a star that is only about 10 light-years away. Considering that the humans were already willing to send a manned mission well past the orbit of Neptune in order to reach Dragon’s Egg in the first place, their propulsion technology is better than what we have now, and there are already plans
in Real Life to make ships that can go a significant fraction of lightspeed, it wouldn’t be too crazy to imagine that humans would just build a slower-than-light ship to reach the star without having knowledge of superluminal travel already. In real life, these plans aren’t being seriously pursued because of the cost and the travel time, but if people knew that they only had to travel 10 light-years before the secret to Casual Interstellar Travel was revealed, I’d think they would try it. They only have to pull it off once, and even if they only make it to 0.5c the round-trip journey could be accomplished in one generation.