Using the Optimistic Oracle V3 to allow for verification of insurance claims.

This section covers the Insurance contract, which is available in the Optimistic Oracle V3 quick-start repo. This tutorial shows an example of how insurance claims can be resolved and settled through the Optimistic Oracle V3 (OOV3) contract.

Insurance Contract

This smart contract allows insurers to issue insurance policies by depositing the insured amount, designating the insured beneficiary, and describing the insured event.

Anyone can request payout to the insured beneficiary at any time. The Insurance contract resolves the claim through the Optimistic Oracle V3 by asserting that the insured event has occurred as of request time using the default identifier ASSERT_TRUTH specified in UMIP-170.

If the claim is confirmed and settled through the Optimistic Oracle V3, this contract automatically pays out insurance coverage to the beneficiary. If the claim is rejected, the policy continues to be active and ready for subsequent claim attempts.

There is no limit to the number of payout requests that can be made of the same policy, however, only the first truthfully resolved request will settle the insurance payment, whereas the Optimistic Oracle V3 will settle bonds for all requests.

Development environment

This project uses forge as the Ethereum testing framework. You will also need to install Foundry, refer to Foundry installation documentation if you don’t have it already.

You will also need git for cloning the repository, as well as bash shell and jq tool in order to parse transaction outputs when interacting with deployed contracts.

Clone the UMA Optimistic Oracle V3 quick-start repository and install the dependencies:

git clone
cd dev-quickstart-oov3
forge install

Contract implementation

The contract discussed in this tutorial can be found at dev-quickstart-oov3/src/Insurance.sol (here) within the repo.

Contract creation and initialization

To initialize the state variables of the contract, the constructor takes two parameters:

  1. _defaultCurrency identifies the token used for settlement of insurance claims, as well as the bond currency for assertions and disputes. This token should be approved as whitelisted UMA collateral. Please check Approved Collateral Types for production networks or call getWhitelist() on the Address Whitelist contract for any of the test networks. Note that the deployed Optimistic Oracle V3 instance already has its defaultCurrency added to the whitelist, so it can also be used by the Insurance contract. Alternatively, you can approve a new token address with addToWhitelist method in the Address Whitelist contract if working in a sandboxed UMA environment.

  2. _optimisticOracleV3 is used to locate the address of UMA Optimistic Oracle V3. Address of OptimisticOracleV3 contact can be fetched from the relevant networks file, if you are on a live network, or you can provide your own contract instance if deploying UMA Oracle contracts in your own sandboxed testing environment.

    constructor(address _defaultCurrency, address _optimisticOracleV3) {
        defaultCurrency = IERC20(_defaultCurrency);
        oo = OptimisticOracleV3Interface(_optimisticOracleV3);
        defaultIdentifier = oo.defaultIdentifier();

Issuing insurance

issueInsurance method allows any insurer to deposit insuranceAmount of defaultCurrency tokens by designating an insurance beneficiary (payoutAddress) and defining the insured event (insuredEvent). Before calling this method, the insurer should have approved this contract to spend the required amount of defaultCurrency tokens.

    function issueInsurance(
        uint256 insuranceAmount,
        address payoutAddress,
        bytes memory insuredEvent
    ) public returns (bytes32 policyId) { ... }

Internally, the issued policy is stored in the policies mapping using the calculated policyId key that is generated by hashing the insured event and beneficiary address.

After pulling insuranceAmount from the caller in the issueInsurance method, the contract emits a InsuranceIssued event including the policyId parameter that should be used when claiming insurance.

Submitting insurance claim

Anyone can submit an insurance claim on the issued policy by calling the requestPayout method with the relevant policyId parameter. This method will make an assertion with the Optimistic Oracle V3. An assertion bond is required, hence the caller should have approved this contract to spend the required minimum amount of defaultCurrency tokens for the proposal bond (call getMinimumBond method on the Optimistic Oracle V3).

    function requestPayout(bytes32 policyId) public returns (bytes32 assertionId) { ... }

After checking that the policyId represents a valid insurance policy, the contract gets the current timestamp and composes claim that the insured event has occurred as of request time, that is passed to the Optimistic Oracle V3 when making the assertion with the assertTruth method:

        assertionId = oo.assertTruth(
                "Insurance contract is claiming that insurance event ",
                " had occurred as of ",
            msg.sender, // asserter
            address(this), // callbackRecipient (the contract)
            address(0), // No sovereign security.
            bytes32(0) // No domain.
        assertedPolicies[assertionId] = policyId;

Optimistic Oracle V3 pulls the required bond and returns assertionId that is used as a key when storing the linked policyId in the assertedPolicies mapping. This information will be required when receiving a callback from the Optimistic Oracle V3.

Disputing insurance claim

For the sake of simplicity this contract does not implement a dispute method, but the disputer can dispute the submitted claim directly through Optimistic Oracle V3 before the liveness passes by calling its disputeAssertion method:

    function disputeAssertion(bytes32 assertionId, address disputer) external nonReentrant { ... }

The disputer should pass the assertionId from the request above, as well as the address for receiving back bond and rewards if the disputer was right.

If the claim is disputed, the request is escalated to the UMA DVM and it can be settled only after UMA voters have resolved it. To learn more about the DVM, see the docs section on the DVM: how does UMA's Oracle work.

Settling insurance claim

Similar to disputes, claim settlement should be initiated through the Optimistic Oracle V3 contract by calling its settleAssertion method with the same assertionId parameter:

    function settleAssertion(bytes32 assertionId) public nonReentrant { ... }

In case the liveness has expired or a dispute has been resolved by the UMA DVM, this call would initiate a assertionResolvedCallback callback in the Insurance contract:

    function assertionResolvedCallback(bytes32 assertionId, bool assertedTruthfully) public { ... }

Importantly, all callbacks should be restricted to accept calls only from the Optimistic Oracle V3 to avoid someone spoofing a resolved answer:

        require(msg.sender == address(oo));

Depending on the resolved answer received in the assertedTruthfully callback parameter, this contract would either pay out the insured beneficiary if this was the first successful claim (in case of true representing that insurance claim was valid) or reject the payout:

        if (assertedTruthfully) _settlePayout(assertionId);
    function _settlePayout(bytes32 assertionId) internal {
        bytes32 policyId = assertedPolicies[assertionId];
        Policy storage policy = policies[policyId];
        if (policy.settled) return;
        policy.settled = true;
        defaultCurrency.safeTransfer(policy.payoutAddress, policy.insuranceAmount);
        emit InsurancePayoutSettled(policyId, assertionId);

Tests and deployment

All the unit tests covering the functionality described above are available here. To execute all of them, run:

forge test --match-path *Insurance*


Before deploying and interacting with the contracts export the required environment variables:

  • ETHERSCAN_API_KEY: your secret API key used for contract verification on Etherscan if deploying on a public network

  • ETH_RPC_URL: your RPC node used to interact with the selected network

  • MNEMONIC: your passphrase used to derive private keys of deployer (index 0) and any other addresses interacting with the contracts

  • FINDER_ADDRESS: address of the Finder contract used to locate other UMA ecosystem contracts (in order to resolve disputes you would need to use the one from a sandboxed environment). For Goerli, you can use:

    export FINDER_ADDRESS=0xE60dBa66B85E10E7Fd18a67a6859E241A243950e
  • DEFAULT_CURRENCY_ADDRESS: address of the token used for insurance claim settlement. This is also used as oracle bonding currency, thus, needs to be added to whitelist either by UMA governance (production networks) or testnet administrator. On Goerli you can use 0xe9448D94C9b033Ff50d3B14089043bD976fC1394 that is already whitelisted and can be minted by anyone using its allocateTo method

Use cast command from Foundry to locate the address of Optimistic Oracle V3:

export OOV3_ADDRESS=$(cast call $FINDER_ADDRESS "getImplementationAddress(bytes32)(address)" \
	$(cast --format-bytes32-string "OptimisticOracleV3"))

To deploy the Insurance contract, run forge create command.

export INSURANCE_ADDRESS=$(forge create --json src/Insurance.sol:Insurance \
	--mnemonic "$MNEMONIC" \
	| jq -r .deployedTo)

Finally, we can verify the deployed (if deployed to a public network) contract with forge verify-contract:

forge verify-contract \
	--chain-id $(cast chain-id) \
	--constructor-args $(cast abi-encode "constructor(address,address)" \

Interacting with deployed contract

The following section provides instructions on how to interact with the deployed contract from the foundry cast tool, though one can also use it for guidance for interacting through another interface (e.g. Remix or Etherscan).

Initial setup

Export required user addresses and their derivation indices:

export INSURER_ID=1
export INSURED_ID=2
export INSURER_ADDRESS=$(cast wallet address --mnemonic "$MNEMONIC" --mnemonic-index $INSURER_ID)
export INSURED_ADDRESS=$(cast wallet address --mnemonic "$MNEMONIC" --mnemonic-index $INSURED_ID)

Make sure the user addresses above have sufficient funding for the gas to execute the transactions.

Issue insurance

Make sure to have some amount of DEFAULT_CURRENCY_ADDRESS tokens to back potential insurance claim. If 0xe9448D94C9b033Ff50d3B14089043bD976fC1394 was used on Goerli you can mint 10,000 DBT tokens to insurance issuer account:

export INSURANCE_AMOUNT=$(cast --to-wei 10000)
cast send --mnemonic "$MNEMONIC" --mnemonic-index $INSURER_ID \

Approve DEFAULT_CURRENCY_ADDRESS to be pulled by the Insurance contract:

cast send --mnemonic "$MNEMONIC" --mnemonic-index $INSURER_ID \

Issue the insurance policy and grab the resulting policyId from the emitted InsuranceIssued event (it should be the last emitted event in the transaction and indexed policyId is at topic index 1):

export ISSUE_TX=$(cast send --json \
	--mnemonic "$MNEMONIC" --mnemonic-index $INSURER_ID \
	"issueInsurance(uint256,address,bytes)" \
	$INSURANCE_AMOUNT $INSURED_ADDRESS $(cast --from-utf8 "Bad things have happened") \
	| jq -r .transactionHash)
export POLICY_ID=$(cast receipt --json $ISSUE_TX | jq -r .logs[-1].topics[1])

If in doubt on the parsing of transaction receipt you can manually view full logs from tracing:

cast run $ISSUE_TX

Submit insurance claim

Get the expected oracle bond:

export BOND_AMOUNT=$(cast call $OOV3_ADDRESS \
	"getMinimumBond(address)(uint256)" $DEFAULT_CURRENCY_ADDRESS)

This should be zero for 0xe9448D94C9b033Ff50d3B14089043bD976fC1394 on Goerli, but in case of other currencies make sure to have this amount of DEFAULT_CURRENCY_ADDRESS both on the insured account (for submitting the claim) and on the insurer's account (for disputing the claim). If bond amount is non-zero, also make sure to add approval:

cast send --mnemonic "$MNEMONIC" --mnemonic-index $INSURED_ID \

Now initiate the insurance claim and grab the resulting assertionId from the emitted InsurancePayoutRequested event (it should be the last emitted event and indexed assertionId is at topic index 2):

export ASSERTION_TX=$(cast send --json \
	--mnemonic "$MNEMONIC" --mnemonic-index $INSURED_ID \
	"requestPayout(bytes32)" $POLICY_ID | jq -r .transactionHash)
export ASSERTION_ID=$(cast receipt --json $ASSERTION_TX | jq -r .logs[-1].topics[2])

If in doubt on the parsing of transaction receipt you can manually view full logs from tracing:

cast run $ASSERTION_TX

Dispute insurance claim

Before liveness passes, anyone (e.g. insurer) can dispute the claim through the Optimistic Oracle V3. In case of non-zero bond amount, they must add approval for Optimistic Oracle V3 to pull the bond:

cast send --mnemonic "$MNEMONIC" --mnemonic-index $INSURER_ID \

Now initiate the dispute and export related transaction hash that we will need to collect additional request parameters for resolving the dispute:

export DISPUTE_TX=$(cast send --json \
	--mnemonic "$MNEMONIC" --mnemonic-index $INSURER_ID \
	$OOV3_ADDRESS "disputeAssertion(bytes32,address)" $ASSERTION_ID $INSURER_ADDRESS \
	| jq -r .transactionHash)

Settle insurance claim

Resolving disputes in production environment involves UMA token holders to vote on the request. Thus, testing is possible only in a sandboxed UMA ecosystem environment where the Mock Oracle is used to resolve requests:

export MOCK_ORACLE_ADDRESS=$(cast call \
	$FINDER_ADDRESS "getImplementationAddress(bytes32)(address)" \
	$(cast --format-bytes32-string "Oracle"))

In order to resolve request Mock Oracle expects the following parameters:

  • identifier: identifier that references instructions to resolve the request (Optimistic Oracle V3 and Insurance contract uses default identifier ASSERT_TRUTH specified in UMIP-170.)

  • time: timestamp when the disputed assertion was made

  • ancillaryData: bytes encoded additional data required to resolve the request (Optimistic Oracle V3 includes assertionId and the address of the claiming asserter)

  • price: numerical value to decide the outcome of the request (Optimistic Oracle V3 requires this to be 1e18 in order to resolve assertion as truthful)

The commands below export the required parameters and resolves the request at the Mock Oracle:

export IDENTIFIER=$(cast call $INSURANCE_ADDRESS "defaultIdentifier()(bytes32)")
export ASSERTION_TIME=$(cast block --json \
	$(cast tx --json $ASSERTION_TX | jq -r .blockNumber) | jq -r .timestamp)
export ANCILLARY_DATA=$(cast --from-utf8 $(echo assertionId:$(echo $ASSERTION_ID | sed 's/0x//' | tr [:upper:] [:lower:]),ooAsserter:$(echo $INSURED_ADDRESS | sed 's/0x//' | tr [:upper:] [:lower:])))

export PRICE=$(cast --to-wei 1)
cast send --mnemonic "$MNEMONIC" --mnemonic-index $INSURED_ID \
	"pushPrice(bytes32,uint256,bytes,int256)" \

Note that the syntax above for getting ancillary data involves stripping 0x and transforming assertionId and ooAsserter to lowercase to replicate the logic how Optimistic Oracle V3 contract is composing the ancillary data. If in doubt, you can always check the emitted PriceRequestAdded event parameters from the Mock Oracle contract in the dispute transaction traces:

cast run $DISPUTE_TX

Now we can settle the request through the Optimistic Oracle V3 and observe the emitted InsurancePayoutSettled from our Insurance contract:

export SETTLE_TX=$(cast send --json \
	--mnemonic "$MNEMONIC" --mnemonic-index $INSURED_ID \
	$OOV3_ADDRESS "settleAssertion(bytes32)" $ASSERTION_ID \
	| jq -r .transactionHash)
cast run $SETTLE_TX

The above settlement transaction should also transfer INSURANCE_AMOUNT tokens to the insured beneficiary as well as return the assertion bond plus half of disputer's bond to the claim initiator.

Alternatively, if 0 value was resolved in PRICE (representing the asserted claim was not true), the settlement transaction should only return the bond plus half of claim initiator's bond to the disputer.

Last updated