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What is
Tracker (Anti-Double-Spend Registry)?
A mutable UTxO on Ergo that maintains a set of redeemed Note IDs — preventing the same Note from being redeemed twice in the agent economy stack.
In Ergo's Note+Reserve+Tracker payment stack, the Tracker is a UTxO box that acts as an on-chain registry of spent Note IDs. When a Note is redeemed, the redemption transaction must include the Tracker box as an input, the Tracker script verifies the Note ID is not already in the spent set, and the transaction outputs a new Tracker containing the updated spent set. This prevents double-redemption without requiring a centralized authority. The Tracker pattern is the eUTXO solution to the double-spend problem for bearer instruments — each UTxO can only be spent once, so the Tracker state is always consistent.
Key Points
- Mutable UTxO tracking spent Note IDs — updated on each redemption
- Redemption transaction must reference Tracker — script verifies no double-spend
- Outputs new Tracker with updated spent set after each redemption
- eUTXO property: Tracker UTxO can only be spent once per transaction
- Stateful but consistent: the chain itself is the source of truth
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This is not financial advice. Ergo has strong fundamentals: fair launch (no VC dump risk), innovative technology (eUTXO, Sigma Protocols, NiPoPoWs), active development, and a cypherpunk ethos. It's a smaller market cap project with higher risk/reward than established chains. Research thoroughly, understand the technology, and never invest more than you can afford to lose.
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