Commit 6c7f366a authored by Adrian Sutton's avatar Adrian Sutton

specs: Remove attestation game specs

Add links to specifications from fault proof docs.
parent f6834953
...@@ -9,7 +9,11 @@ finalized and may change without notice. ...@@ -9,7 +9,11 @@ finalized and may change without notice.
### Contents ### Contents
* Overview * Specifications
* [Generic Fault Proof System](../../specs/fault-proof.md)
* [Generic Dispute Game Interface](../../specs/dispute-game-interface.md)
* [Fault Dispute Game](../../specs/fault-dispute-game.md)
* [Cannon VM](../../specs/cannon-fault-proof-vm.md)
* [Deployment Details](./deployments.md) * [Deployment Details](./deployments.md)
* [Manual Usage](./manual.md) * [Manual Usage](./manual.md)
* [Creating Traces with Cannon](./cannon.md) * [Creating Traces with Cannon](./cannon.md)
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...@@ -3,7 +3,7 @@ ...@@ -3,7 +3,7 @@
The `op-challenger` is a modular **op-stack** challenge agent The `op-challenger` is a modular **op-stack** challenge agent
written in golang for dispute games including, but not limited to, attestation games, fault written in golang for dispute games including, but not limited to, attestation games, fault
games, and validity games. To learn more about dispute games, visit the games, and validity games. To learn more about dispute games, visit the
[dispute game specs](../specs/dispute-game.md). [fault proof specs](../specs/fault-proof.md).
## Quickstart ## Quickstart
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...@@ -29,8 +29,9 @@ that maintains 1:1 compatibility with Ethereum. ...@@ -29,8 +29,9 @@ that maintains 1:1 compatibility with Ethereum.
Specifications of new features in active development. Specifications of new features in active development.
- [Fault Proof](./fault-proof.md) - [Fault Proof](./fault-proof.md)
- [Dispute Game](./dispute-game.md)
- [Dispute Game Interface](./dispute-game-interface.md) - [Dispute Game Interface](./dispute-game-interface.md)
- [Fault Dispute Game](./fault-dispute-game.md)
- [Cannon VM](./cannon-fault-proof-vm.md)
## Design Goals ## Design Goals
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...@@ -20,14 +20,14 @@ be attached to an output proposal. In this case, the bond will be paid in ether. ...@@ -20,14 +20,14 @@ be attached to an output proposal. In this case, the bond will be paid in ether.
By requiring a bond to be posted with an output proposal, spam and invalid outputs By requiring a bond to be posted with an output proposal, spam and invalid outputs
are disincentivized. Explicitly, if invalid outputs are proposed, challenge agents are disincentivized. Explicitly, if invalid outputs are proposed, challenge agents
can delete the invalid output via a [dispute-game](./dispute-game.md) and seize the can delete the invalid output via a [dispute-game](./dispute-game-interface.md) and seize the
proposer's bond. So, posting invalid outputs is directly disincentivized in this way proposer's bond. So, posting invalid outputs is directly disincentivized in this way
since the proposer would lose their bond if the challenge agents seize it. since the proposer would lose their bond if the challenge agents seize it.
Concretely, outputs will be permissionlessly proposed to the `L2OutputOracle` contract. Concretely, outputs will be permissionlessly proposed to the `L2OutputOracle` contract.
When submitting an output proposal, the ether value is sent as the bond. This bond is When submitting an output proposal, the ether value is sent as the bond. This bond is
then held by a bond manager contract. The bond manager contract is responsible for then held by a bond manager contract. The bond manager contract is responsible for
both the [dispute-games](./dispute-game.md) and the `L2OutputOracle` (further detailed both the [dispute-games](./dispute-game-interface.md) and the `L2OutputOracle` (further detailed
in [proposals](./proposals.md)). in [proposals](./proposals.md)).
The bond manager will need to handle bond logic for a variety of different The bond manager will need to handle bond logic for a variety of different
...@@ -136,7 +136,7 @@ instead tied to the address of the output proposer. ...@@ -136,7 +136,7 @@ instead tied to the address of the output proposer.
## Bond Manager Implementation ## Bond Manager Implementation
Initially, the bond manager will only be used by the `L2OutputOracle` contract Initially, the bond manager will only be used by the `L2OutputOracle` contract
for output proposals in the attestation [dispute game](./dispute-game.md). Since for output proposals in the attestation [dispute game](./dispute-game-interface.md). Since
the attestation dispute game has a permissioned set of attestors, there are no the attestation dispute game has a permissioned set of attestors, there are no
intermediate steps in the game that would require bonds. intermediate steps in the game that would require bonds.
......
# Challenger Specification
<!-- START doctoc generated TOC please keep comment here to allow auto update -->
<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
**Table of Contents**
- [Description](#description)
- [Terminology](#terminology)
- [Event and Response Lifecycle](#event-and-response-lifecycle)
- [`GameType.FAULT`](#gametypefault)
- [`GameType.ATTESTATION`](#gametypeattestation)
- [`GameType.VALIDITY`](#gametypevalidity)
<!-- END doctoc generated TOC please keep comment here to allow auto update -->
## Description
The Challenger is an off-chain agent that listens for faulty claims made about the state of
the L2 on the data availability layer. It is responsible for challenging these incorrect claims
and ensuring the correctness of all finalized claims on the settlement layer.
The Challenger agent is intended to be ran as a permissionless service by participants of the network
alongside a [rollup-node](./rollup-node.md). Challenger agents will be rewarded in the form of the
bond attached to the claims they disprove.
## Terminology
- **data availability layer** - In the context of this document, the data availability layer is the
generic term for the location where claims about the state of the layer two are made. In the context
of Optimism, this is Ethereum Mainnet.
- **settlement layer** - In the context of this document, the settlement layer is the location of the
bridge as well as where funds deposited to the rollup reside. In the context of Optimism, this is
Ethereum Mainnet.
- **L2** - In the context of this document, the layer two of the Optimistic Rollup. In the context
of Optimism, this is the Optimism Mainnet.
- **rollup-node** - In the context of this document, the rollup node describes the
[rollup-node specification](./rollup-node.md). In the context of Optimism, this is the implementation
of the [rollup-node specification](./rollup-node.md), the `op-node`.
## Event and Response Lifecycle
The Challenger agent is expected to be able to listen for and respond to several different events
on the data availability layer. These events and responses are parameterized depending on the type
of dispute game being played, and the Challenger listens to different events and responds uniquely
to each of the different game types. For specification of dispute game types, see the
[Dispute Game Interfaces specification](./dispute-game-interface.md) and
[Dispute Game specification](./dispute-game.md).
### `GameType.FAULT`
> **Warning**
> The `FAULT` game type is not yet implemented. In the first iteration of Optimism's decentralization effort,
> challengers will respond to `ATTESTATION` games only.
**Events and Responses**
*TODO*
### `GameType.ATTESTATION`
**Events and Responses**
- [`L2OutputOracle.OutputProposed`](../packages/contracts-bedrock/src/L1/L2OutputOracle.sol#L57-70)
The `L2OutputOracle` contract emits this event when a new output is proposed on the data availability
layer. Each time an output is proposed, the Challenger should check to see if the output is equal
the output given by the `optimism_outputAtBlock` endpoint of their `rollup-node`.
- If it is, the Challenger should do nothing to challenge this output proposal.
- If it is not, the Challenger should respond by creating a new `DisputeGame` with the
`DisputeGameType.ATTESTATION` `gameType`, the correct output root as the `rootClaim`, and the abi-encoded
`l2BlockNumber` of the correct output root as the `extraData`.
![Attestation `OutputProposed` Diagram](./assets/challenger_attestation_output_proposed.png)
- `DisputeGameFactory.DisputeGameCreated` A new dispute game has been created and is ready to be reviewed. The
Challenger agent should listen for this event and check if the `rootClaim` of the `AttestationDisputeGame`
created by the `DisputeGameFactory` is equal to the output root of their `rollup-node` at the game's `l2BlockNumber`.
- If it is, the Challenger should sign the [EIP-712 typeHash](./dispute-game.md) of the struct containing the
`AttestationDisputeGame`'s `rootClaim` and `l2BlockNumber`. The Challenger should then submit the abi-encoded
signature to the `AttestationDisputeGame`'s `challenge` function.
- If it is not, the Challenger should do nothing in support of this dispute game.
![Attestation `DisputeGameCreated` Diagram](./assets/challenger_attestation_dispute_game_created.png)
A full diagram and lifecycle of the Challenger's role in the `ATTESTATION` game type can be found below:
![Attestation Diagram](./assets/challenger_attestation.png)
### `GameType.VALIDITY`
**TODO**
> **Warning**
> The `VALIDITY` game type is not yet implemented. In the first iteration of Optimism's decentralization effort,
> challengers will respond to `ATTESTATION` games only. A validity proof based dispute game is a possibility,
> but fault proof based dispute games will be the primary focus of the team in the near future.
**Events and Responses**
*TODO*
# Dispute Game
<!-- START doctoc generated TOC please keep comment here to allow auto update -->
<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
**Table of Contents**
- [Attestation Dispute Game](#attestation-dispute-game)
- [Smart Contract Implementation](#smart-contract-implementation)
- [Attestation Structure](#attestation-structure)
- [Why EIP-712](#why-eip-712)
<!-- END doctoc generated TOC please keep comment here to allow auto update -->
## Attestation Dispute Game
The output attestation based dispute game shifts the current permissioned output proposal process
to a permissionless, social-consensus based architecture that can progressively decentralize over
time by increasing the size of the signer set. In this "game," output proposals can be submitted
permissionlessly. To prevent "invalid output proposals," a social quorum can revert an output proposal
when an invalid one is discovered. The set of signers is maintained in the `SystemConfig` contract,
and these signers will issue [EIP-712](https://eips.ethereum.org/EIPS/eip-712) signatures
over canonical output roots and the `l2BlockNumber`s they commit to as attestations. To learn more,
see the [DisputeGame Interface Spec](./dispute-game-interface.md).
In the above language, an "invalid output proposal" is defined as an output proposal that represents
a non-canonical state of the L2 chain.
### Smart Contract Implementation
The `AttestationDisputeGame` should implement the `IDisputeGame` interface and also be able to call
out to the `L2OutputOracle`. It is expected that the `L2OutputOracle` will grant permissions to
`AttestationDisputeGame` contracts to call its `deleteL2Outputs` function at the *specific* `l2BlockNumber`
that is embedded in the `AttestationDisputeGame`'s `extraData`.
The `AttestationDisputeGame` should be configured with a quorum ratio at deploy time. It should also
maintain a set of attestor accounts, which is fetched by the `SystemConfig` contract and snapshotted
at deploy time. This snapshot is necessary to have a fixed upper bound on resolution cost, which in
turn gives a fix cost for the necessary bond attached to output proposals.
The ability to add and remove attestor accounts should be enabled by a single immutable
account that controls the `SystemConfig`. It should be impossible to remove accounts such that quorum
is not able to be reached. It is ok to allow accounts to be added or removed in the middle of an
open challenge, as it will not affect the `signerSet` that exists within open challenges.
A challenge is created when an alternative output root for a given `l2BlockNumber` is presented to the
`DisputeGameFactory` contract. Multiple challenges should be able to run in parallel.
For simplicity, the `AttestationDisputeGame` does not need to track what output proposals are
committed to as part of the attestations. It only needs to check that the attested output root
is different than the proposed output root. If this is not checked, then it will be possible
to remove output proposals that are in agreement with the attestations and create a griefing vector.
#### Attestation Structure
The EIP-712 [typeHash](https://eips.ethereum.org/EIPS/eip-712#rationale-for-typehash) should be
defined as the following:
```solidity
TYPE_HASH = keccak256("Dispute(bytes32 outputRoot,uint256 l2BlockNumber)");
```
The components for the `typeHash` are as follows:
- `outputRoot` - The **correct** output root that commits to the given `l2BlockNumber`. This should be a
positive attestation where the `rootClaim` of the `AttestationDisputeGame` is the **correct** output root
for the given `l2BlockNumber`.
- `l2BlockNumber` - The L2 block number that the `outputRoot` commits to. The `outputRoot` should commit
to the entirety of the L2 state from genesis up to and including this `l2BlockNumber`.
### Why EIP-712
It is important to use EIP-712 to decouple the originator of the transaction and the attestor. This
will allow a decentralized network of attestors that serve attestations to bots that are responsible
for ensuring that all output proposals submitted to the network will not allow for malicious withdrawals
from the bridge.
It is important to have replay protection to ensure that attestations cannot be used more than once.
...@@ -412,5 +412,5 @@ The allocated response time is limited by the dispute-game window, ...@@ -412,5 +412,5 @@ The allocated response time is limited by the dispute-game window,
and any additional time necessary based on L1 fee changes when bonds are insufficient. and any additional time necessary based on L1 fee changes when bonds are insufficient.
> Note: the timed, bonded, bisection dispute game is in development. > Note: the timed, bonded, bisection dispute game is in development.
> Also see [dispute-game specs](./dispute-game.md) for general dispute game system specifications, > Also see [fault dispute-game specs](./fault-dispute-game.md) for fault dispute game system specifications,
> And [dispute-game-interface specs](./dispute-game-interface.md) for dispute game interface specifications. > And [dispute-game-interface specs](./dispute-game-interface.md) for dispute game interface specifications.
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