did:cow, a proposal for an ID resolution method with most of the convenience of did:plc/did:web and the robustness of a public blockchain
A bit of extra validation
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web/static/index.html
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web/static/index.html
···
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An ID can be created for free without a blockchain transaction. You only need to send a blockchain transaction if you want to point it at a different did:web or did:plc ID, or change the blockchain address that controls it.
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<br />
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<br />
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<a style="float:right" href="/#!/did:cow:B6aaa1DAd9D09d689dc6111dcc6EA2A0d641b406:plc:pyzlzqt6b2nyrha7smfry6rv">Example</a>
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<a href="https://tangled.org/goat.navy/did-cow">Specification</a>
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<a href="/#!/did:cow:B6aaa1DAd9D09d689dc6111dcc6EA2A0d641b406:plc:pyzlzqt6b2nyrha7smfry6rv">Example</a>
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<a href="https://api.cow.watch/did:cow:B6aaa1DAd9D09d689dc6111dcc6EA2A0d641b406:plc:pyzlzqt6b2nyrha7smfry6rv">API</a>
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···
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const CONTRACT_ABI = [
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"function updateController(address _controller, string _wrappedDID, address _newController)",
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"function updateWrappedDID(address _controller, string _wrappedDID, string _newWrappedDID)",
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"error NotController()",
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"error NotInitialized()",
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"error AlreadyDeactivated()",
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"error EmptyWrappedDID()",
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];
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const CONTRACT_ERROR_MESSAGES = {
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"0x23019e67": "The connected wallet is not the current controller of this DID.",
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"0x87138d5c": "This DID has not been registered on-chain yet.",
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"0x5deafd90": "This DID has been permanently deactivated.",
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"0x8a98f156": "Wrapped DID cannot be empty.",
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};
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let contractConfig = null;
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···
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// Pre-fill controller with checksummed address (strip 0x for did:cow format)
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const controllerInput = document.getElementById("create-controller");
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if (!controllerInput.value) {
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controllerInput.value = toChecksumAddress(connectedAddress).slice(2);
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controllerInput.value = ethers.getAddress(connectedAddress).slice(2);
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}
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document.getElementById("controller-hint").style.display = "inline";
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// Enable edit fields if a DID has already been resolved
···
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}
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};
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// EIP-55 checksum — minimal implementation
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function toChecksumAddress(address) {
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const addr = address.toLowerCase().replace("0x", "");
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// Use the browser's SubtleCrypto to keccak would require a library;
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// ethers is loaded below for this — call after ethers loads.
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return address; // placeholder; replaced once ethers is available
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}
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// ── Resolve ─────────────────────────────────────────────────────────────────
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let resolvedDid = null; // the DID last successfully resolved, for contract calls
···
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document.getElementById("edit-wrapped-btn").disabled = !enabled;
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}
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function extractDid(input) {
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// Strip a full cow.watch URL if pasted, e.g. https://cow.watch/#!/did:cow:...
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input = input.trim().replace(/^https?:\/\/[^/]+\/#!\//, "");
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// Also handle bare hash e.g. #!/did:cow:...
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input = input.replace(/^#!\//, "");
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return input;
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}
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window.resolveDid = async () => {
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const did = document.getElementById("resolve-did").value.trim();
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const did = extractDid(document.getElementById("resolve-did").value);
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if (!did) {
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const statusEl = document.getElementById("resolve-status");
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statusEl.style.display = "block";
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statusEl.className = "result error";
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statusEl.textContent = "Please enter a did:cow DID.";
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return;
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}
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document.getElementById("resolve-did").value = did; // normalise the field
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window.location.hash = "!/" + did;
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const statusEl = document.getElementById("resolve-status");
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const resultEl = document.getElementById("resolve-result");
···
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controller = controller.slice(2);
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}
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// Strip leading did: if present
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if (wrapped.startsWith("did:")) {
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wrapped = wrapped.slice(4);
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}
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wrapped = stripDidPrefix(wrapped);
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if (!controller) {
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showCreateError("Controller address is required.");
···
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requestAnimationFrame(frame);
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}
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function stripDidPrefix(s) {
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// Remove one or more leading "did:" repetitions
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while (s.startsWith("did:")) s = s.slice(4);
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return s;
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}
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// ── Edit ────────────────────────────────────────────────────────────────────
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function parseCowDid(did) {
···
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let tx;
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if (updateType === "controller") {
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const raw = document.getElementById("edit-controller").value.trim().replace(/^0x/i, "");
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if (!/^[0-9a-fA-F]{40}$/.test(raw)) throw new Error("Invalid controller address");
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if (!raw) throw new Error("Controller address is required.");
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if (!/^[0-9a-fA-F]{40}$/.test(raw)) throw new Error("Invalid controller address — expected a 40-character hex Ethereum address.");
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tx = await contract.updateController(controller, wrapped, "0x" + raw);
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} else {
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let newWrapped = document.getElementById("edit-wrapped").value.trim();
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if (newWrapped.startsWith("did:")) newWrapped = newWrapped.slice(4);
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if (!newWrapped.includes(":")) throw new Error("Invalid wrapped DID");
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let newWrapped = stripDidPrefix(document.getElementById("edit-wrapped").value.trim());
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if (!newWrapped) throw new Error("Wrapped DID is required.");
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if (!newWrapped.includes(":")) throw new Error("Wrapped DID must include a method, e.g. plc:xxx or web:example.com");
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tx = await contract.updateWrappedDID(controller, wrapped, newWrapped);
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}
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···
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statusEl.textContent = `Confirmed in block ${receipt.blockNumber}\nTx: ${tx.hash}`;
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} catch (e) {
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statusEl.className = "result error";
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statusEl.textContent = e.reason ?? e.message ?? String(e);
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if (e.code === "CALL_EXCEPTION") {
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const selector = typeof e.data === "string" ? e.data.slice(0, 10) : null;
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statusEl.textContent = CONTRACT_ERROR_MESSAGES[selector] ?? `Contract reverted${selector ? ` (${selector})` : ""}`;
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} else if (e.code === "UNKNOWN_ERROR" || e.message?.includes("coalesce")) {
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// MetaMask sometimes returns a malformed RPC response after broadcasting
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// even though the tx went through.
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statusEl.className = "result success";
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statusEl.textContent = "Transaction sent — check your wallet for confirmation status.";
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} else {
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statusEl.textContent = e.reason ?? e.message ?? String(e);
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}
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}
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};
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