Zero knowledge UTXO set inclusion proof, that's very promising! 

Proof time 6 min, 
Proof size 1.4 MB, 
Verification time 300 ms

https://github.com/halseth/utxozkp

https://delvingbitcoin.org/t/proving-utxo-set-inclusion-in-zero-knowledge/1142 

 very nice