Verify EVM signatures offline: EIP-191 personal messages, EIP-712 typed data, and x402/EIP

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0x15459498e1191d8787c83177809bd54022fA18c4",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "2000",
    "maxTimeoutSeconds": 300
  }
]

{
  "bazaar": {
    "info": {
      "input": {
        "body": {
          "address": "0x7E5F4552091A69125d5DfCb7b8C2659029395Bdf",
          "message": "Busker x402 verify-sig example",
          "signature": "0x8f83ce1348bb56eb6d7ede8f6c6787adc3897839e686a0b305fb87e7cd248d5555c7405f0e776b995be1971d6ed71a95541d19635e354f807d94c9326c22a1cb1c"
        },
        "bodyType": "json",
        "method": "POST",
        "type": "http"
      },
      "output": {
        "body": {
          "amount": "object — { usdc } for known USDC contracts",
          "authorization": "object (authorization modes) — from, to, value, validAfter, validBefore, nonce",
          "checks": "object (x402-header) — payToMatches, amountMatches, network, scheme",
          "matches": "boolean (when address given) / matchesFrom (authorization modes)",
          "messageHash": "string (eip191) / digest (typed modes)",
          "mode": "string (eip191|eip712|eip3009|x402-header)",
          "signer": "string|null — recovered EOA",
          "valid": "boolean — signature recovered to an address",
          "window": "object — { validAfter, validBefore, validNow }"
        },
        "bodyType": "json",
        "example": {
          "address": "0x7E5F4552091A69125d5DfCb7b8C2659029395Bdf",
          "matches": true,
          "messageHash": "0x0c9b1f4d5f2b6e7a4d3c2b1a0f9e8d7c6b5a4f3e2d1c0b9a8f7e6d5c4b3a2f1e",
          "mode": "eip191",
          "signer": "0x7E5F4552091A69125d5DfCb7b8C2659029395Bdf",
          "valid": true
        }
      }
    },
    "routeTemplate": "/verify-sig",
    "schema": {
      "properties": {
        "input": {
          "additionalProperties": false,
          "properties": {
            "body": {
              "additionalProperties": false,
              "description": "Exactly one of: message (EIP-191), typedData (EIP-712), authorization (EIP-3009 / x402 exact-EVM), paymentHeader (raw base64 Payment-Signature or X-Payment header). signature is required except with paymentHeader.",
              "properties": {
                "address": {
                  "description": "Expected signer; when given the response carries a matches boolean.",
                  "type": "string"
                },
                "authorization": {
                  "description": "EIP-3009 TransferWithAuthorization fields { from, to, value, validAfter, validBefore, nonce } (the x402 payload.authorization object).",
                  "type": "object"
                },
                "domain": {
                  "description": "Explicit EIP-712 domain { name, version, chainId, verifyingContract } for a non-USDC token.",
                  "type": "object"
                },
                "message": {
                  "description": "Plain message that was signed with personal_sign (EIP-191).",
                  "type": "string"
                },
                "network": {
                  "description": "CAIP-2 network for authorization mode (default eip155:8453 = USDC on Base).",
                  "type": "string"
                },
                "paymentHeader": {
                  "description": "Raw base64 value of an x402 Payment-Signature / X-Payment header; decoded and verified in one step.",
                  "type": "string"
                },
                "signature": {
                  "description": "0x-prefixed 65-byte signature.",
                  "type": "string"
                },
                "typedData": {
                  "description": "EIP-712 payload { domain, types, primaryType, message } exactly as signed.",
                  "type": "object"
                }
              },
              "type": "object"
            },
            "bodyType": {
              "enum": [
                "json"
              ],
              "type": "string"
            },
            "method": {
              "enum": [
                "POST"
              ],
              "type": "string"
            },
            "type": {
              "const": "http",
              "type": "string"
            }
          },
          "required": [
            "type",
            "method",
            "bodyType",
            "body"
          ],
          "type": "object"
        }
      }
    }
  }
}

curl "https://workbot1.oddsys.org/verify-sig"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

const res = await fetch("https://workbot1.oddsys.org/verify-sig");
if (res.status === 402) {
  const { accepts } = await res.json();
  // pay one of accepts[] via an x402 client, then retry with the payment header
}

import httpx
res = httpx.get("https://workbot1.oddsys.org/verify-sig")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header