Stellar’s Silent Upgrade Unlocks Zero-Knowledge Proofs for Soroban Smart Contracts

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Stellar’s Quietest Upgrade Just Changed Everything

On January 22nd, Stellar was updated to Protocol 25, nicknamed ‘X-Ray.’ This upgrade allows developers to add zero-knowledge (ZK) proofs directly into Soroban smart contracts by incorporating the BN254 elliptic curve and Poseidon hash function.

On January 22nd, the validators who keep the Stellar network running voted to upgrade to a new version, nicknamed X-Ray (Protocol 25). The upgrade happened seamlessly, and regular users didn’t even notice a change. The network continued to operate perfectly.

Stellar typically launches updates quietly, and this one is no exception. However, the recent X-Ray upgrade is quite significant. According to @BuildOnStellar on X, it adds the BN254 elliptic curve and initial support for the Poseidon hash function directly into the Soroban smart contract platform.

These two advancements are significant. BN254 and Poseidon are fundamental to many current zero-knowledge proof systems, and adding native support for them on the blockchain is a major upgrade, not just a small fix.

The Cryptography Nobody Is Talking About Yet

Zero-knowledge proofs allow you to demonstrate knowledge of a secret without actually sharing the secret itself. This technology is built on complex math using elliptic curve cryptography, and BN254 is a specific system that enables this.

Poseidon is a type of hash function designed for use in zero-knowledge circuits. It’s more efficient to calculate within a proof compared to older methods.

By working together, they’re enabling advanced proving systems – like Groth16, PLONK, and Ultrahonk – to function on Stellar. These systems are crucial for technologies such as rollups, secure voting, and digital identity verification. A recent post by BuildOnStellar on X highlighted that BN254 is also being integrated into several Ethereum standards, specifically EIP-196 and EIP-197.

The Soroban SDK documentation actually warns that certain functions are like “hazardous materials.” This immediately signals that they are basic, powerful tools – not simple things to play around with.

A Sudoku Game That Proves More Than You Think

PamphileRoy, a guest writer from the AHCO, recently created a complete demo of zero-knowledge (ZK) technology on the Stellar network, as discussed in a thread on X (formerly Twitter). The demo is a Sudoku game where players prove they’ve solved the puzzle without actually revealing their solution on the blockchain.

This circuit is built using Noir, a relatively new programming language for zero-knowledge proofs that’s gaining popularity. It relies on Barretenberg, Noir’s core engine, which utilizes the Ultrahonk proving system. Finally, a smart contract interacts with a pre-existing Ultrahonk verifier contract that’s already live on the Stellar network.

One line does the verification. Just one cross-contract call. That simplicity is the whole point.

Why This Is Bigger Than One Demo

The Sudoku example demonstrates how Stellar can be used for learning purposes, but the technology powering it is robust enough for real-world applications. Now, any program needing to verify calculations without sharing its data can operate on the Stellar network.

This enables private identity verification and allows complex computations done outside the main network to be securely recorded on-chain. Ultimately, it makes Layer 2 rollup technology feasible on a network that’s already fast and affordable.

BuildOnStellar recently announced on X that their platform, Scaffold Stellar, now allows developers to quickly turn smart contracts into complete decentralized applications (dApps) – in just minutes. They already had the necessary command-line tools, a local node setup, and basic scaffolding, and they’ve just added zero-knowledge (ZK) technology. This completes the full development stack they’ve been building.

The Tools Are Ready, but Caution Applies

The recent post from BuildOnStellar emphasizes that security shouldn’t be compromised when working with Zero-Knowledge (ZK) technology. They stress the importance of having ZK specialists formally audit the circuits, as even a small error could completely ruin user privacy.

The Stellar Community Fund has a dedicated fund to pay for security audits. This is especially helpful for independent developers who don’t have the resources to afford them on their own.

PamphileRoy noted on X that suggestions for improving the demo are welcome. They mentioned features like support for multiple puzzles, a timed winner selection process, and the ability for administrators to control the puzzles – all of which are now technically feasible with the current network setup.

The developers of the Ultrahonk verifier on Stellar were also recognized, as were the teams from Noir and Stellar Development Foundation (SDF) who integrated BN254 and Poseidon into the core Stellar protocol.

The recent X-Ray upgrade from Stellar didn’t generate much initial buzz, which is typical for their releases. However, it’s a significant step forward, bringing zero knowledge proofs directly into a platform already handling real-world payments on a global scale.

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2026-03-31 19:19