{"uid":"cap_qfoSSZUPrfuA91tG0Hna3","slug":"attestpage-sha-256-timestamping-service-3c71a46a","name":"AttestPage SHA-256 Timestamping Service","description":"Signs a timestamped receipt for a file's sha256, proving it existed unchanged then. US$0.002 per call; POST the hash.","url":"https://s2h6qt73jtzlgbgnnfacln2poq.srv.us/v1/attest?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"note":{"type":"string","maxLength":280,"description":"Optional note; only its SHA-256 goes in the receipt."},"sha256":{"type":"string","pattern":"^[0-9a-fA-F]{64}$","description":"SHA-256 (hex) of the thing being attested."},"idempotency_key":{"type":"string","maxLength":128,"description":"Optional, x402 payments only (keys are scoped to the paying address; trial and L402 calls get 400). Retries with the same key and sha256 get the same attestation (the receipt names that call own payment tx); a different sha256 gets 409."}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.002","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"registry","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.002/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.002","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.002","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_PGWF8vOh9qcz6m2NMrFR8","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.002","costPer":"request","priority":0,"asset":"0x036CbD53842c5426634e7929541eC2318f3dCF7e","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Creates a signed, timestamped cryptographic receipt for a SHA-256 hash, proving a file or record existed unchanged at a specific point in time","exampleAgentPrompt":"Attest this SHA-256 hash for me — e4d909c290d0fb1ca068ffaddf22cbd0d3e9a7b4b7e5c3c7f4f3c5b7a1d2e3f4 — and include the note 'Q2 financial report final version' so I have a signed timestamped receipt proving it existed right now.","exampleUseCases":[{"title":"Audit trail for AI-generated answers","prompt":"I need a tamper-proof timestamped receipt for this AI response before I send it to the client — here's the SHA-256: a3f1c2d4e5b6789012345678abcdef0123456789abcdef0123456789abcdef01. Add the note 'AI legal memo draft v1 sent to Acme Corp'."},{"title":"Prove software build integrity","prompt":"We're shipping version 2.4.1 of our firmware today — can you create an attestation receipt for this build hash b94d27b9934d3e08a52e52d7da7dabfac484efe04f8c8b4b5c1c4c3d2e1f0a9b with the note 'firmware-v2.4.1 release build'?"},{"title":"Legal document existence proof","prompt":"I need to prove this signed contract existed before the deadline — please timestamp the SHA-256 hash 0f1e2d3c4b5a6978abcdef0123456789abcdef0123456789abcdef0123456789 with the note 'NDA signed by both parties prior to merger announcement'."}],"resultDescription":"A signed, timestamped cryptographic receipt confirming that the submitted SHA-256 hash was attested at a specific moment in time. The receipt is verifiable: any future version of the file that produces a different hash will not match, proving tampering or alteration. With an idempotency key, retrying the same hash returns the identical original receipt rather than creating a new record.","failureModes":["Invalid SHA-256 format (not 64 hex characters) returns a 400 error","Idempotency key used with a different sha256 than the original returns 409 Conflict","Idempotency key used outside of x402 payment context returns 400","Payment not completed or insufficient funds prevents attestation","Note exceeds 280 character limit returns validation error","Network timeout or service unavailability returns 5xx error"],"whenToPreferThis":"Use this endpoint when you need cryptographic, verifiable proof that a specific file, record, or piece of data existed unchanged at a given point in time — without revealing the content itself (only the hash is submitted). Prefer this over simple database logging when the proof needs to be independently verifiable and tamper-evident. Use /v1/fetch instead when you need to attest what a live web page said at a given time, as that endpoint captures and hashes the page contents itself.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-17T12:30:12.898Z","isFirstParty":false,"canonicalSlug":"attestpage-sha-256-timestamping-service-3c71a46a"}