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The cannon (cannon cannon cannon) is an on chain interactive dispute engine implementing EVM-equivalent fault proofs.

It's half geth, half MIPS, and whole awesome.

• It's Go code
• ...that runs an EVM
• ...emulating a MIPS machine
• ...running compiled Go code
• ...that runs an EVM

For more information on Cannon's inner workings, check this overview.

Directory Layout

minigeth -- A standalone "geth" capable of computing a block transition
mipigo -- minigeth compiled for MIPS. Outputs a MIPS binary that's run and mapped at 0x0
mipsevm -- A MIPS runtime in the EVM (works with contracts)
contracts -- A Merkleized MIPS processor on chain + the challenge logic

Building

Pre-requisites: Go, Node.js, Make, and CMake.

make build
make test # verify everything works correctly

Examples

The script files demo/challenge_simple.sh and demo/challenge_fault.sh present two example scenarios demonstrating the whole process of a fault proof, including the challenge game and single step verification.

• In the simple challenge, the challenger uses the wrong block data in his challenge.
• In the fault scenario, fault injection is used to alter the challenger's memory at a specific step of the execution.

In both cases, the challenger fails to challenge the block. Refer to the documentation string at the top of these file for more details regarding the scenario.

State Oracle API

On chain / in MIPS, we have two simple oracles

• InputHash() -> hash
• Preimage(hash) -> value

We generate the Preimages in x86 using geth RPC

• PrefetchAccount
• PrefetchStorage
• PrefetchCode
• PrefetchBlock

These are NOP in the VM

License

Most of this code is MIT licensed, minigeth is LGPL3.

Note: This code is unaudited. It in NO WAY should be used to secure any money until a lot more testing and auditing are done. I have deployed this nowhere, have advised against deploying it, and make no guarantees of security of ANY KIND.