Gas Killer is a new approach to scaling computation on Ethereum. Instead of executing expensive calculations and storage reads on-chain, Gas Killer uses EigenCloud to simulate transactions off-chain and write back only the essential storage updates. The key innovation is replacing complex on-chain operations with simple aggregate signature verification. Gas Killer is able to save gas specifically on all internal reads, some external reads and computation. So any storage writes needed will still need to be paid for through gas fees and the aggregate signature verification will also incur a cost every time Gas Killer is used. The aggregate signature verification cost is the Turetzky Upper Gas Limit (TUGL) which we have estimated currently to be at around 250k gas.

Learn more about how Gas Killer works here.

This means that no matter how computationally intensive a smart contract function is, Gas Killer can theoretically reduce its gas consumption to just the cost of verifying a signature (250k gas) and updating state. For privacy protocols, which rely on heavy cryptographic operations, this represents a fundamental shift in economics where privacy can be more affordable for everyone.

In this case study, we'll break down how we calculated Gas Killer to be able to cut gas costs in half for Railgun, one of the most popular privacy protocols on Ethereum. We specifically analyzed their Relay contract and its two main methods, shield and transact.

Railgun is a privacy protocol that allows users to conduct shielded transactions on Ethereum while maintaining compatibility with some DeFi protocols. Railgun enables you to hide transaction details (sender, recipient, amount) by converting public funds into "shielded" funds, which are then kept private until withdrawal. To do this they use zero-knowledge cryptography, specifically zero-knowledge Succinct Non-Interactive Arguments of Knowledge (zk-SNARKs), to prove transaction validity without revealing the underlying data.

However, privacy on Ethereum comes at a steep cost. Railgun enables users to shield their transactions and protect their financial privacy, but the complex zero-knowledge proofs and cryptographic operations required mean users can pay a hefty fee for a single private transfer. While Railgun has recently experienced an increase in usage and interest with the Kohaku wallet announcement from the Ethereum Foundation, this cost barrier has prevented privacy from becoming accessible to everyday users, limiting adoption to only those who can afford the premium, making decreasing the costs paramount to adoption of privacy preserving protocols.

One of Railgun’s main smart contracts is its Relay contract which has two main methods:

Shield: Converts public tokens into private shielded tokens by depositing them into the privacy pool using zero-knowledge proofs. This creates a commitment that hides the depositor's identity while proving they own the funds.

Shield method calls tend to hover around 720k to 750k gas.

Transact: Performs private transfers, withdrawals, or interactions with DeFi protocols. This function processes the zero-knowledge proofs that verify the transaction is valid without exposing the sender, receiver, or amount.

Transact method calls can range from 450k to 1.15M gas.

Both operations involve computationally expensive cryptographic verification that consume substantial amounts of gas. There are more complexities to the system but we focused on these two methods for this analysis.

To help us with understanding the savings that Gas Killer can potentially yield, we created the Gas Analyzer, a tool that simulates historical transactions as if they were routed through Gas Killer to identify the savings possible. By feeding actual Railgun transactions through the tool, we can pinpoint approximately how much gas savings Gas Killer could achieve for Railgun and its users in its current state.

The analyzer examines the execution trace of historical transactions, categorizing gas consumption by operation type and calculating potential savings. Gas Killer is able to abstract away all operations that are internal reads and computation as well as some external reads.

For this analysis we took 100 shield and 300 transaction method calls that were performed successfully during the month of October 2025 and calculated the potential Gas Killer gas savings using the Gas Analyzer tool. We created a dataset for each method that included the gas used for the original method call as well as savings output when run through the Gas Analyzer.

For shield method calls our results showed that Gas Killer could save 40.9% in gas savings on average and for transact method calls we found a 53.9% gas savings on average. Our analysis showed that an integration with Gas Killer could cut total gas costs nearly in half for users of Railgun!

These savings are expected in large part because zero-knowledge proofs are still computationally expensive on Ethereum. If you’re interested in seeing whether Gas Killer can get your app or protocol some gas savings then reach out at contact@bread.coop or press the button below.

At the moment we’re still hard at work on getting to mainnet but it shouldn’t be too much longer. But let’s say Gas Killer was already deployed on mainnet, what would be the next steps for Railgun to integrate Gas Killer and pass on savings in gas to users?

First it would require potentially one of the easiest contract upgrades possible. Railgun developers would need to add one line of code per method which would point them to the Gas Killer network to be computed. Once that is done, then all shield and transact method calls would be sent to the network which would return the output onchain with BLS signature aggregation. And that’s really about it.

But what happens if there’s something wrong with the network?

Gas Killer is designed so that no operator of the network is able to return an incorrect or fallacious output. If they do, it is rejected via the protocol and the operator risks getting slashed. If there is a situation where the network is down or something similar where a transaction cannot be pushed through Gas Killer, the transaction defaults to run onchain, the old school way. Therefore, integrating Gas Killer introduces very few new risks for protocols and applications. Gas Killer avoids being a bottleneck while providing gas savings for users.

Privacy should not be a luxury reserved for those who can afford expensive gas fees. Cutting Railgun gas costs in half would make privacy within reach for more users and in turn make its privacy pool stronger. This democratization of privacy is essential for adoption.

With the Ethereum Foundation’s renewed focus on cypherpunk values and the proliferation of zero-knowledge proof implementations, Gas Killer is important infrastructure for scaling privacy.