How to run a challenger for Moca Chain

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Challenger Information

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Minimum System Requirements

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Setting up a challenger

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Prerequisite

• Pull the develop branch of the moca-challenger repository.
• The deployment of moca-challenger relies on validator binding initialization. If you want to deploy your own moca-challenger, you need to join as a new validator.

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Challenger Introduction

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Moca-challenger main components

• Monitor: Polls the Moca blockchain to obtain new blocks, parse challenge events, and add them to the local database.
• Verifier: Verifies the integrity of the stored data by comparing root hashes.
• Vote Broadcaster: Broadcasts a signed vote on the blockchain for events that failed verification.
• Vote Collector: Polls the blockchain for votes broadcast by other Challenger services.
• Vote Collator: Collates votes to achieve a 2/3 consensus.
• Tx Submitter: Sends a MsgAttest to the blockchain after enough consensus votes are received.
• Attest Monitor: Polls the blockchain for successfully attested challenges and updates the database.

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Deploy moca-challenger

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Configuration file

"moca_config": {
    "key_type": "local_private_key",
    "private_key": "your_challenger_private_key",
    "bls_private_key": "your_bls_private_key",
    "rpc_addrs": [ "https://tm-rpc.testnet.mocachain.dev" ],
    ...
},
"db_config": {
    "dialect": "mysql",
    "db_path": "tcp(127.0.0.1:3306)/challenger?charset=utf8&parseTime=True&loc=Local",
    ...
},
"sp_config": {
    "internal_sp_endpoints": [
      "https://gateway.storage-provider-0.testnet.mocachain.dev",
      "https://gateway.storage-provider-1.testnet.mocachain.dev",
      "https://gateway.storage-provider-2.testnet.mocachain.dev"
    ]
}

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Run locally

Running MySQL in Docker

docker run -p 3306:3306 --name moca -e MYSQL_ROOT_PASSWORD=moca -d mysql:8

Create a database

mysql --port=3306 -h127.0.0.1 -uroot -pmoca
CREATE SCHEMA IF NOT EXISTS challenger DEFAULT CHARACTER SET utf8 COLLATE utf8_unicode_ci;

Get validator BLS key and challenger key

./build/mocad keys export ${BLS_KEY_NAME} --unsafe --unarmored-hex --home=${CLIENT_KEYRING_DIR} --keyring-backend=test
./build/mocad keys export ${CHALLENGER_NAME} --unsafe --unarmored-hex --home=${CLIENT_KEYRING_DIR} --keyring-backend=test

Compile and launch moca-challenger

make build
./build/moca-challenger --config-type local --config-path ./config/config.json

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Test and Verification

Create your own SP

1. Authorization: Grant spending limits.
2. Submit a proposal: Use a JSON template to create a storage provider.

Tampering with data stored on SP

1. Create a bucket and upload a file.
2. Find the storage directory on your SP and modify the content of the data chunk file.

./build/moca-cmd --home deployment/localup/ bucket create --primarySP 0x...yourSPAddress moca1
./build/moca-cmd --home deployment/localup/ object put --contentType "application/octet-stream" ./abctest moca://moca1/abctest

Challenge the data chunk of the object

• Regular challenge: Moca automatically generates random data availability challenges. The moca-challenger monitors these events. If data has been tampered with, the root hashes will not match, and the challenge will be successful. The validator will vote, and if 2/3 consensus is reached, the SP will be slashed.
• Manual challenge: Anyone can submit a transaction to challenge data availability.

Data recovery

1. Data is automatically recovered after a successful data challenge.
2. Data is automatically recovered when users find that the data is unreadable.
3. SPs can selectively recover lost data through tools.