01
Once
Each credit is retired once.
Retirements are recorded as serial ranges in standard lots. The contract refuses any range that overlaps an earlier retirement, and anyone can check a serial.
OnceSealed · carbon credit retirements
Prove a credit was retired once, without publishing who retired it.
OnceSealed records each retirement on-chain as a serial range and a commitment hash. The buyer’s identity stays encrypted for an accredited auditor, and every project-quality finding cites the paragraph of the source document it came from.
Three principles
02
Sealed
Buyer identity is encrypted; the auditor can verify it.
Only a commitment hash goes on-chain. The buyer’s LEI is encrypted to the auditor, who checks it and attests the result on-chain once. Not zero-knowledge: a hash commitment plus encryption.
03
Evidence-backed
Every AI finding cites the source PDF.
Each “found” check points to a paragraph of the project’s public Verra documents, shown with its page. A “found” without a cited paragraph is not counted, and a second model’s disagreement is marked for review.
Explore the prototype
PublicProject qualityMethodology status and five principle findings for 11 real Verra projects.Registry operatorRetire creditsRetire whole lots of simulated serials for a fictional buyer and issue a private receipt.AnyoneVerify a retirementLook up a retirement or serial and check a receipt against the chain.AuditorAudit queueOpen the sealed identity, review the checks and attest once.AssessorAssess a projectAdd a registry document, run the checks, compare the draft and anchor a new report version.