Does MCDx / USDC match its issuer's published contract?

QED signs a canonical JSON payload. Fetch the public key from /.well-known/qed.json, then check the signature against this payload.

Canonical JSON

{"block":26220562,"chain":"ethereum","checked_at":"2026-10-18T16:12:07Z","dev":false,"expires_at":"2026-10-19T16:12:07Z","issuer":"Backed xStocks","pool":{"base":{"address":"0x80A77a372c1e12AcCdA84299492f404902E2DA67","balance":"196862062938344386","decimals":18,"symbol":"MCDx"},"chain":"ethereum","dex":"uniswap-v4","pool":"0x3440ba3895d6a0f96860579e73778275b9b2bb4adba353015cd57ba8a9814694","quote":{"address":"0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48","balance":"63774156","decimals":6,"symbol":"USDC"}},"quote_share_of_supply":5.9258939181342095e-6,"reads":[{"block":null,"method":"eth_call","params":["0xbd216513d74c8cf14cf4747e6aaa6420ff64ee9e","poolKeys","0x3440ba3895d6a0f96860579e73778275b9b2bb4adba353015c"],"raw_result":"Object {\"currency0\": String(\"0x80a77a372c1e12accda84299492f404902e2da67\"), \"currency1\": String(\"0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48\"), \"fee\": String(\"880000\"), \"hooks\": String(\"0x0000000000000000000000000000000000000000\"), \"tickSpacing\": String(\"17600\")}","result_hash":"d851892a1d2841db5415bda81b48eb6e14446c57e22c7d4b5064bfa39cd06561","slot":null},{"block":null,"method":"eth_call","params":["0x7ffe42c4a5deea5b0fec41c94c136cf115597227","getSlot0","0x3440ba3895d6a0f96860579e73778275b9b2bb4adba353015cd57ba8a9814694"],"raw_result":"true","result_hash":"18d10c7d2b4b04aaf04254d1ae5d655a5dc0407cbcdd5a8c3986e985370f36ee","slot":null},{"block":null,"method":"eth_call","params":["0x7ffe42c4a5deea5b0fec41c94c136cf115597227","getLiquidity","0x3440ba3895d6a0f96860579e73778275b9b2bb4adba353015cd57ba8a9814694"],"raw_result":"3543262918437","result_hash":"4876b86df2119432f8706260cc3f025b18c850105d4c9b91c6d7bb261c3a404a","slot":null},{"block":null,"method":"eth_call","params":["0x80A77a372c1e12AcCdA84299492f404902E2DA67","symbol()"],"raw_result":"Some(\"MCDx\")","result_hash":"e7d5fe82bd500ad41c17edd3dc09824b578e31804fbbe175cc0b450d4396a0e7","slot":null},{"block":null,"method":"eth_call","params":["0x80A77a372c1e12AcCdA84299492f404902E2DA67","decimals()"],"raw_result":"Some(18)","result_hash":"c14f173ff30df32f36fac2ea29d9a20482082428fd32b58be5433d310884f764","slot":null},{"block":null,"method":"eth_call","params":["0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48","symbol()"],"raw_result":"Some(\"USDC\")","result_hash":"a3c9e246b0832b52e41efce041d8614251f5e288cdd4b192e85bfd3dfcb748ff","slot":null},{"block":null,"method":"eth_call","params":["0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48","decimals()"],"raw_result":"Some(6)","result_hash":"c68fe6989b1835302197d0af5be845dfab10ed9f9632205eb4ab5b949b9e1a6a","slot":null},{"block":26220562,"method":"eth_blockNumber","params":[],"result_hash":"72d59e9977a0f1dd8c072346a7196dc334ab7b279039aacbb1ea2b3c86a43726","slot":null},{"block":null,"method":"eth_call","params":["0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48","symbol()"],"raw_result":"Some(\"USDC\")","result_hash":"a3c9e246b0832b52e41efce041d8614251f5e288cdd4b192e85bfd3dfcb748ff","slot":null},{"block":null,"method":"eth_call","params":["0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48","name()"],"raw_result":"Some(\"USD Coin\")","result_hash":"fe94af15dc887a2c9df1fb0d6d276e6c586ca9d430ffeac0d05e4baee0637fd1","slot":null},{"block":null,"method":"eth_call","params":["0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48","decimals()"],"raw_result":"Some(6)","result_hash":"c68fe6989b1835302197d0af5be845dfab10ed9f9632205eb4ab5b949b9e1a6a","slot":null},{"block":null,"method":"eth_call","params":["0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48","totalSupply()"],"raw_result":"Some(\"48241909609038877\")","result_hash":"93117fc71be3bd673639b228c25516bd34e15fba5c8b174b92c22b3ab15da48a","slot":null},{"block":null,"method":"eth_call","params":["0x80A77a372c1e12AcCdA84299492f404902E2DA67","symbol()"],"raw_result":"Some(\"MCDx\")","result_hash":"e7d5fe82bd500ad41c17edd3dc09824b578e31804fbbe175cc0b450d4396a0e7","slot":null},{"block":null,"method":"eth_call","params":["0x80A77a372c1e12AcCdA84299492f404902E2DA67","name()"],"raw_result":"Some(\"McDonald's xStock\")","result_hash":"d3e1675b3c54a529a2b91ef66fafa6f9e8f58ecf9256ff601e438c45ea0cf3ec","slot":null},{"block":null,"method":"eth_call","params":["0x80A77a372c1e12AcCdA84299492f404902E2DA67","decimals()"],"raw_result":"Some(18)","result_hash":"c14f173ff30df32f36fac2ea29d9a20482082428fd32b58be5433d310884f764","slot":null},{"block":null,"method":"eth_call","params":["0x80A77a372c1e12AcCdA84299492f404902E2DA67","totalSupply()"],"raw_result":"Some(\"33220652556049662648414\")","result_hash":"f47e8ef94e7fc7a7acbc4b84fd016148b3e5ad6a252f50a0fa10db90aeb5503f","slot":null},{"block":null,"method":"eth_getCode","params":["0x80A77a372c1e12AcCdA84299492f404902E2DA67","latest"],"result_hash":"71ee049d0c0cab5d785d7aef2e6b591e511475fb8ef465f4d8f5335bfd412bfd","slot":null},{"block":null,"method":"eth_getCode","params":["0x80A77a372c1e12AcCdA84299492f404902E2DA67","latest"],"result_hash":"71ee049d0c0cab5d785d7aef2e6b591e511475fb8ef465f4d8f5335bfd412bfd","slot":null}],"registry_entry":{"chain":"ethereum","contract":"0x80A77a372c1e12AcCdA84299492f404902E2DA67","decimals":null,"issuer":"Backed xStocks","last_checked":"2026-10-18T15:47:32Z","name":"McDonald's","official_deployments":[{"address":"0x80a77a372c1e12accda84299492f404902e2da67","network":"Ethereum","wrapper_address":"0x1717d8be2bcb27f4e8f36c817088fa6a2c0b3b30","wrapper_address_v2":"0xc6639026a3a862cd4fcbae3f67cb2d25a2959d37"},{"address":"0x80a77a372c1e12accda84299492f404902e2da67","network":"BinanceSmartChain","wrapper_address":"0x1717d8be2bcb27f4e8f36c817088fa6a2c0b3b30","wrapper_address_v2":"0xc6639026a3a862cd4fcbae3f67cb2d25a2959d37"},{"address":"0x80a77a372c1e12accda84299492f404902e2da67","network":"Arbitrum","wrapper_address":"0x1717d8be2bcb27f4e8f36c817088fa6a2c0b3b30","wrapper_address_v2":"0xc6639026a3a862cd4fcbae3f67cb2d25a2959d37"},{"address":"XsqE9cRRpzxcGKDXj1BJ7Xmg4GRhZoyY1KpmGSxAWT2","network":"Solana"},{"address":"TCVJcRqEEpkbs2iSJtMumoTqPxrKPwCLaW","network":"Tron"},{"address":"EQBUtLkOu9vzKu3PW58c50WX7w89BtzwYYZlZGmvOr_Aq66U","network":"Ton"},{"address":"0x80a77a372c1e12accda84299492f404902e2da67","network":"Mantle","wrapper_address":"0x1717d8be2bcb27f4e8f36c817088fa6a2c0b3b30","wrapper_address_v2":"0xc6639026a3a862cd4fcbae3f67cb2d25a2959d37"},{"address":"0x80a77a372c1e12accda84299492f404902e2da67","network":"HyperEVM","wrapper_address_v2":"0xc6639026a3a862cd4fcbae3f67cb2d25a2959d37"},{"address":"0x80a77a372c1e12accda84299492f404902e2da67","network":"Ink","wrapper_address_v2":"0xc6639026a3a862cd4fcbae3f67cb2d25a2959d37"},{"address":"0x80a77a372c1e12accda84299492f404902e2da67","network":"XLayer","wrapper_address_v2":"0xc6639026a3a862cd4fcbae3f67cb2d25a2959d37"},{"address":"0x80a77a372c1e12accda84299492f404902e2da67","network":"Optimism","wrapper_address_v2":"0xc6639026a3a862cd4fcbae3f67cb2d25a2959d37"},{"address":"0x80a77a372c1e12accda84299492f404902e2da67","network":"Monad","wrapper_address_v2":"0xc6639026a3a862cd4fcbae3f67cb2d25a2959d37"}],"source":"xstocks-api","source_url":"https://api.xstocks.fi/api/v2/public/assets","ticker":"MCD"},"registry_hash":"2bf13ff4020924ba1c74d8e732c3dd1609679a3b9a6dc8a796250beb0ae1b589","signer":"GJWKkiUd3zj1pJGfeE7JitiPiwDJC6XmNFvpJWJuvvpn","slot":null,"subject":"0x3440ba3895d6a0f96860579e73778275b9b2bb4adba353015cd57ba8a9814694","ticker":"MCD","verdict":{"Verified":{"issuer":"Backed xStocks","ticker":"MCD"}},"version":1}

Signature

mys6RrzsGlRGNVMCAs0YQuyHTAjZQtghVh4syTiv8//kLVHiE6qvZJu2qwClUtK01WmiICtuyNxQ42pPsRhvAg==

API call

GET /api/attest/efeb346b965979884aa95d781e514d8d75a9b7416749a6cd58bd059622cd6acb

1. Fetch the public key and attestation JSON, then verify the signature with the published key.
2. Canonicalize the payload with sorted object keys and no whitespace, then verify its SHA-256 attestation id.
3. Run the API call above and compare the returned payload, serial, signer, and signature with this certificate.