Blockchain Privacy — Zama Developer Program
Zama | Protecting Onchain Financial Strategies
A Bleu project that protects the budget and individual offers during a token buyback, with the total purchased disclosed afterward.
On public blockchains, anyone can track transactions. This makes operations easy to observe, but it can also expose financial decisions before they are completed. Privacy layers can help protect this information and the strategy behind an operation.
Bleu explored this challenge through a token buyback. Protocols that issue their own tokens often use revenue to buy those tokens back. The aim is to support the token's price and reward investors. However, when a buy order is visible, other participants can anticipate demand, buy before the protocol does, and sell afterward at a higher price. The protocol may end up paying more per token and buying fewer tokens with the same budget.
What we built: a buyback with confidential offers
Confidential Buybacks is a proof of concept created for the Zama Developer Program Builder Track. In the demo, an organization sets a budget, and token holders submit sell offers specifying a token amount and a minimum price. Unlike a public order, the token amounts and price limits are encrypted.
These values are processed without being revealed during the operation. The project uses fully homomorphic encryption (FHE), a technology that allows calculations on encrypted data without decrypting it during processing. Zama's documentation explains how this approach applies to smart contracts.
When a round ends, participants can check whether their sell orders were successful and claim their tokens.
Demonstrating the solution
Bleu built a working demo on the Sepolia testnet. The flow includes confidential offers, calculations that stay within the budget, payment or token refunds, and disclosure of the round's total afterward.
The project still uses demo tokens and a simulated reference price. It remains a proof of concept, with no audit or production use.
The impact on blockchain financial operations
Confidential Buybacks explores a way to protect the budget and individual offers while a buyback is underway, then publish the total purchased afterward. The idea addresses a broader challenge in decentralized finance: how to keep operations verifiable without revealing information in advance that could influence the market. Protecting amounts during execution can help limit the exposure of financial strategies; disclosing an aggregate result afterward provides a way to report what happened without publishing each individual offer.
The same challenge can arise in payments, scheduled token distributions, and treasury management. This proof of concept demonstrates an approach to buybacks; it does not yet validate those other applications.