{"uid":"cap_YIKX2IdjMDcj0fmht5kEF","slug":"eip-191-ethereum-message-hash-personal-sign-digest-31a4deff","name":"EIP-191 Ethereum Message Hash (personal_sign digest)","description":"EIP-191 digest of a message (what personal_sign actually signs) — Genesis402 / UnyKorn Operator Network","url":"https://twin.unykorn.org/eth-message-hash?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"params":{"type":"object","properties":{"message":{"type":"string","maxLength":49152}}}}},"responseSchema":{"type":"json","example":{"ok":true,"type":"eth-message-hash","receipt":{"tx_hash":"0x<64hex>","amount_usd":0.001,"receipt_id":"g402-<16hex>"},"generated_at":"<iso8601>"}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.001","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","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":"$0.001/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_s7-ptwHJN1SWkqb05xsVJ","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.001","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Computes the EIP-191 prefixed hash of a message string — the exact digest that Ethereum wallets sign during personal_sign","exampleAgentPrompt":"What is the EIP-191 hash that Ethereum's personal_sign would actually sign for the message 'Please sign this to confirm your identity: nonce=abc123'?","exampleUseCases":[{"title":"Verify off-chain signature authenticity","prompt":"I need to verify that a user actually signed my login challenge message. Can you compute the EIP-191 personal_sign hash for 'Login to MyApp: nonce=7f3a9c' so I can compare it against the signature they submitted?"},{"title":"Debug Ethereum signing flow","prompt":"My dApp's signature verification is failing — what EIP-191 hash does personal_sign actually produce for the message 'Authorize withdrawal of 100 USDC on 2024-06-01'? I want to check if my backend is computing it correctly."},{"title":"Prepare message digest for smart contract","prompt":"I'm writing a smart contract that checks personal_sign signatures. Can you give me the EIP-191 prefixed hash for the string 'Transfer approved: user=0xABCD, amount=500' so I can hardcode the expected digest in my test?"}],"resultDescription":"Returns a JSON object confirming success, the type field 'eth-message-hash', and the computed EIP-191 digest (the keccak256 hash of the '\\x19Ethereum Signed Message:\\n{len}{message}' prefixed payload), along with a payment receipt including transaction hash, USD amount, and receipt ID.","failureModes":["Message exceeds 49152 character limit — request rejected","Malformed JSON body or missing message field — 400 error","Payment not received or insufficient — 402 error","Service unavailable on the UnyKorn network — 503 or timeout"],"whenToPreferThis":"Use this endpoint when you need to reproduce or verify the exact hash that an Ethereum wallet computes during a personal_sign (eth_sign) operation — without running a local Ethereum node or wallet. Ideal for off-chain signature verification, backend authentication systems, smart contract testing, and debugging signing flows where you need to confirm the prefixed keccak256 digest independently.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-01T18:55:43.787Z","isFirstParty":false,"canonicalSlug":"eip-191-ethereum-message-hash-personal-sign-digest-31a4deff"}