Scaling Zcash: How Project Tachyon and Valar Aim to Push Shielded Transactions to Visa-Level Speeds

The quest to scale privacy-centric blockchains has long been one of the most formidable challenges in the digital asset industry. While transparent networks like Bitcoin and Ethereum have made strides with layer-2 scaling solutions, networks that prioritize absolute user privacy face unique cryptographic hurdles. For Zcash, a pioneer in shielded transactions, the throughput of private transactions has historically been limited by the sheer computational weight of its underlying technology.

To achieve mainstream adoption, a blockchain must compete with traditional payment giants. Mastercard and Visa process more than 50,000 transactions per second, a benchmark that the Zcash development team calls ‘“its floor, not its target.”’ However, achieving this scale under Zcash’s current cryptography presents a massive data bottleneck. If the network were to process transactions at that speed today, a node would need to take in and verify more than 500 megabytes of data every second to keep up. This is because every private transaction carries a proof, and proofs are large.

To put that into perspective, 500 megabytes per second is roughly a full DVD of data arriving every ten seconds, continuously. Currently, no current Zcash software runs anywhere near that capacity, as requiring intense cryptographic computations on such a massive scale quickly overwhelms standard node infrastructure. The math behind zero-knowledge proofs is highly secure, but the sheer volume of data generated at high throughput remains a major barrier.

Fortunately, developers are actively working on architectural overhauls to bypass these physical limits. Cryptographer Sean Bowe’s Project Tachyon is tackling this by working on recursive proofs, in which one proof attests to the validity of thousands of others, dramatically reducing the amount of data that must be checked at consensus.

Under Tachyon, a node verifies a single proof instead of the thousands. The team says this breakthrough reduces the requirement for consensus data from 100 megabytes per second to 500 megabytes, a level they claim is technically achievable with careful engineering. By compressing the verification pipeline, the network can maintain its robust security and privacy guarantees without demanding impossible bandwidth from its node operators.

However, solving the network’s consensus throughput is only half the battle. Wallets have a different problem. In a transparent blockchain, a wallet can simply query a public server to find transactions associated with its public address. Because Zcash hides who a transaction is for, a wallet cannot ask a server which transactions belong to it without giving itself away and exposing its financial privacy.

To maintain confidentiality, a Zcash wallet must download the entire block history and decrypt every transaction locally to see if it is the intended recipient. It pulls down everything and tests each one, which is why wallet software tops out at about one transaction per second. This scanning lag has long been a pain point for everyday users of shielded assets.

To resolve this user-side bottleneck, developers are introducing Valar’s PIR solution. Valar leverages a cryptographic technique known as Private Information Retrieval to solve the wallet scanning dilemma. Private Information Retrieval allows a client to query a database and retrieve specific information without the database server learning what was queried. By implementing this technology, Zcash wallets will be able to privately fetch only their relevant transactions from a server, removing the need to download and scan the entire blockchain locally. Together, Project Tachyon and Valar represent a dual-pronged approach to scaling, clearing the path for private digital cash to operate at global commercial scale.