Does COST / USDG 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

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Dollar\")","result_hash":"e34c795a5a7df6a2269bde7247321204357731d7742ef5974b04eb6899db8b11","slot":null},{"block":null,"method":"eth_call","params":["0x5fc5360D0400a0Fd4f2af552ADD042D716F1d168","decimals()"],"raw_result":"Some(6)","result_hash":"c68fe6989b1835302197d0af5be845dfab10ed9f9632205eb4ab5b949b9e1a6a","slot":null},{"block":null,"method":"eth_call","params":["0x5fc5360D0400a0Fd4f2af552ADD042D716F1d168","totalSupply()"],"raw_result":"Some(\"696496200347174\")","result_hash":"c89de63b57cbd2df29547c452103566aa72dd3f4abac92a6142add18e0bbbedd","slot":null},{"block":null,"method":"eth_call","params":["0x4EA005168D7F09a7A0Ba9D1DEf21a479950E44C2","symbol()"],"raw_result":"Some(\"COST\")","result_hash":"866c851612ec17e501644f2fb18b29f624346d0d90fda37e71b74b497fdfb534","slot":null},{"block":null,"method":"eth_call","params":["0x4EA005168D7F09a7A0Ba9D1DEf21a479950E44C2","name()"],"raw_result":"Some(\"Costco • Robinhood Token\")","result_hash":"3306e3c590cae7c2a7afba84f8a6337483c2399bb2828ca3e34a19cae89832cd","slot":null},{"block":null,"method":"eth_call","params":["0x4EA005168D7F09a7A0Ba9D1DEf21a479950E44C2","decimals()"],"raw_result":"Some(18)","result_hash":"c14f173ff30df32f36fac2ea29d9a20482082428fd32b58be5433d310884f764","slot":null},{"block":null,"method":"eth_call","params":["0x4EA005168D7F09a7A0Ba9D1DEf21a479950E44C2","totalSupply()"],"raw_result":"Some(\"787342804810000000000\")","result_hash":"523ee7f5b525d397522509d7e3b64886d9d2a588648418378da0236174830acd","slot":null},{"block":null,"method":"eth_call","params":["0x4EA005168D7F09a7A0Ba9D1DEf21a479950E44C2","uiMultiplier()"],"raw_result":"1000612040296259656","result_hash":"8e61b2cd50da99c2ae832fa44c79dc1736a4e9d00f5b8a7af4fde5a82a06cad5","slot":null},{"block":null,"method":"eth_getCode","params":["0x4EA005168D7F09a7A0Ba9D1DEf21a479950E44C2","latest"],"result_hash":"e023f4a2e14683cf62969bf3dc7d7821b1e293e30ebe17f3bc5fd0b223173f25","slot":null},{"block":null,"method":"eth_getCode","params":["0x4EA005168D7F09a7A0Ba9D1DEf21a479950E44C2","latest"],"result_hash":"e023f4a2e14683cf62969bf3dc7d7821b1e293e30ebe17f3bc5fd0b223173f25","slot":null}],"registry_entry":{"chain":"robinhood","contract":"0x4EA005168D7F09a7A0Ba9D1DEf21a479950E44C2","decimals":18,"issuer":"Robinhood","last_checked":"2026-10-18T18:54:09Z","name":"Costco","official_deployments":[{"address":"0x4EA005168D7F09a7A0Ba9D1DEf21a479950E44C2","network":"Robinhood Chain"}],"source":"robinhood-registry","source_url":"https://api.robinhood.com/rhj/assets","ticker":"COST"},"registry_hash":"e40a8f7ec2f1a2c1d6467a45e0976602299513549c0406d646df02a3ecb928c8","signer":"GJWKkiUd3zj1pJGfeE7JitiPiwDJC6XmNFvpJWJuvvpn","slot":null,"subject":"0x0a2121A50A09eD0796ae81F9c53fF9398355a398","ticker":"COST","verdict":{"Verified":{"issuer":"Robinhood","ticker":"COST"}},"version":1}

Signature

NVthxTYLcZ1JvwsmMaBlhXm+hNS1ji1F8nYUYuHF7DjmFUyh6mR346XJuRePgZIwuEJ6fXB/rRkT8NvwlJ7MDQ==

API call

GET /api/attest/c8ae8b0981c67e4ff359642947df95da544ffd1f3b47face8ce27bd7700b9774

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.