This is all from a twitter thread: https://twitter.com/secparam/status/1380352749859135489
Mobilecoin is in Signal. What would it have taken to put Zcash there instead? Signal wanted 1) fast payments (< 5 seconds) 2) capacity/scale. “Snarks are slow” you heard. So clearly Zcash needs new crypto break throughs and it’s out in the cold until there’s new science? Nope.
Zcash in Signal needed fast payments and scale. So you need a blockchain with fast (say sub 5 second) confirmations. You won’t get that from traditional PoW. Maybe DAG protocols. And BFT or PoS works. Thankfully, Zcash’s tech is consensus agnostic, we just need a blockchain.
So switch to PoS or a DAG. Done. But now you need scale to handle all those users. That probably requires years of new R&D right? Well, no. Once you’ve swapped consensus algorithms, you can easily handle more than enough zkSNARK transactions today. So no problem there.
Finally, for fast payments you need zkSNARK proof generation to be fast. It’s 2 seconds on mobile now. Not fast enough for you? I disagree, but theres at least 2 to 3x speedups in simple optimizations in the circuit and/or proving code. Couple of weeks of work to mock up.
So, to put Zcash or its tech in Signal, you’d need to move to a faster consensus algorithm like DAG/BFT/PoS and optimize your proving code/circuit. That’s it. You’d get fast < 5 second private payments that can handle thousands of payments per second.
There are two ways to look at this. 1) is we missed the boat. I don’t think thats it. Instead we are much better positioned for the next one. But this requires doing a number of things differently post halo.