This treasury proposal aims to retro-actively cover the first 28 person days of completed work on implementing privacy sidechains for any substrate based chain. This benefits Polkadot and Kusama relaychains but also all their parachains and even solochains - without the need to change a single thing in their runtimes!
Detailed Proposal and Discussion Thread
Blog post about why privacy matters and our longer term vision
brenzi's presentation at Polkadot Now India 2023 [video, 12min]