[darrenf]

Sounds to me like you're describing GridCoin[0], which operates on top of BOINC[1] which itself was spawned from Seti@Home.

[0] https://gridcoin.us/ [1] https://en.wikipedia.org/wiki/Berkeley_Open_Infrastructure_f...

Edited to add footnote: no affiliation or familiarity with GridCoin! Just that the concept described rang a bell, and I was able to find the link.