5 Upgrades That Can Turn Zcash into Private Money at Scale

Ladder remains the holy grail of privacy channels. Fortunately for the Zcash community, its builders have a plan to increase private ZEC payments. And better yet, the first step on that path is happening this week.

In “The Complete Zcash Roadmap”, the latest episode of Bankless, the co-founder of Zcash Sean Bowe and protocol contributor Dev Ojha explained to David Hoffman how it’s possible to take Zcash from around 60 KB of throughput per second today to Ojha’s long-term goal of 50,000 transactions per second (i.e. 100 MB per second, an increase of 166,500%!).

Today’s article will introduce you to five of the upgrades that will be cornerstones of this vision.

As I noted when the NU7 timeline was locked in September, Zcash’s 9th major network upgrade will reduce block times from 75 seconds to 25 seconds. The activation height of NU7 is ready to land on the night of November 5 to 6 (UTC).

Since the block size remains the same, this change will be roughly triple channel bandwidth at ~180 KB per second, per Ojha. From there, he pointed out tricks that other chains already use, like erasure coding (i.e. splitting blocks into redundant pieces so that nodes can rebuild them without downloading everything) and more intelligent gossip between nodes.

Notably, Zcash does all of this while also sticking to proof of work. Ojha hailed this as an effort to “achieve high-throughput proof of work for the first time ever.” However, there’s a quirk to consider here: Mining is random, so at an average of 25 seconds, he said about 1% of blocks would land in about 250 milliseconds, while another about 1% would take more than 110 seconds.

Upgrade status: Faster blocks should go live with NU7 this week. The most difficult work in terms of throughput is what Ojha described as work “over the next couple of years.”

As Ojha said: “The hard problem is how do you know you’ve been paid?

With Zcash-protected addresses, no one can see who paid who, so your wallet can’t just request your balance from a server. Instead, Zcash wallets have historically downloaded each transaction to check which ones were theirs, which would collapse once the chain reached 100 MB per second.

Alas, report recovery of private information (PIR). In this paradigm, your wallet would send an encrypted request to a server holding the chain’s data, and then the server would send the response back without ever learning what you requested thanks to homomorphic encryption (i.e. calculations performed directly on encrypted data).

Interestingly, AI is one of the main reasons why this system is now practical. According to Ojha, this type of PIR boils down to giant matrix-vector multiplications, which is precisely the area where math GPUs have become cheap and fast amid the current AI boom.

In fairness, David emphasized the obvious concern that questioning a server looks like a trusted intermediary. Ojha’s response was that PIR would work like RPCs on Ethereum, where anyone can create their own provider and wallets can switch between multiple of them.

Upgrade status: Already used! Bowe says Zcash used PIR in a recent coin holder vote, which he says was a first for any crypto project.

Tachyon is Bowe’s overhaul of cryptography, and it specifically addresses two bottlenecks. The first concerns proofs, since today a full node verifies the zero-knowledge proof of each protected transaction. one by one.

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To this end, Tachyon develops recursive SNARKs (i.e. proofs that verify other proofs) to group them together. This technique would reduce the responsibility of a full node to simply checking one ZKP launched here and there instead of multiple standalone ZKPs sequentially.

Notably, this system can provide at least a 5x scaling improvement immediately as soon as it rolls out, and if that sounds familiar, that’s because it is. David compared Tachyon’s proof work to the way ZK aggregates transactions on Ethereum, which Ojha credited to Ethereum for pioneering recursive proofs in production.

Upgrade status: In development. The tachyon code is being integrated in the crypto stack behind the Zakura full node, but it has not been activated on mainnet and there is currently no public launch date.

Tachyon’s second objective targets the swelling of the state. Every time someone passes a protected ZEC, the network records a canceller (i.e. a unique marker that prevents the same funds from being spent twice), and unlike transparent chains, which can erase old data, privacy chains must maintain this ever-growing list.

Tachyon also works to compress this state. According to Ojha, full nodes would only retain about the last month of their operating state, while older history would become something you can query without trust when needed. Bowe attributes the technique to a paper he co-wrote with the cryptographer Ian Miers.

To be clear, Ojha was blunt in saying that “you can’t send 50,000 TPS to a Raspberry Pi”, but at this scale, a node could only needs a few hundred gigabytes of storage instead of something like a petabyte.

Upgrade status: Currently in development as part of Tachyon.

The latest upgrade is more about the economy, and it’s also the first of the bunch.

On Ethereum or Solana, wallet companies like MetaMask and Phantom pay for RPC servers (i.e. the infrastructure that feeds your wallet chain data), in part because they can monetize users. Zcash does not track its users, so today a handful of providers provide this data for free.

To avoid “relying on altruism,” Ojha outlined a private subscription model. You would pay upfront for, say, 1,000 requests per month, your wallet would turn that into unique tokens, and each request would burn a token using the same double-spending prevention tricks that Zcash uses for payments.

So, in this paradigm, providers would be able to verify a valid subscription without knowing it. which asks the subscriber.

Upgrade status: Conceptual for now, although Ojha presented it as a problem that can certainly be fixed.

As for why any of this matters NOWBowe’s case was that AI made it trivial to track people through transparent records.

Beyond this intrigue, the new episode of the roadmap Also discusses Zcash’s post-quantum plans, formal verification, and governance, the latter of which pairs well with my recent look at the Zcash development funds debate.