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Running a Challenger

⚠️ This section may change without prior notice
Critical information in this section may be subject to change as the network is in early stages.
🔒 Repo not publicly available — please reach out to us if you would like to run this code.

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Challenger Information

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Minimum System Requirements

ComponentMinimum Specification
HardwareDesktop or laptop running recent versions of Mac OS X or Linux
CPU4 cores
Memory (RAM)12 GB
Storage1 TB HDD/SSD
Bandwidth1 MB/s

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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

Moca ensures data integrity by regularly issuing challenge events to storage providers to prove that stored data has not been tampered with. This service allows end-users to monitor challenge events in the blockchain and perform verification.

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Moca-challenger main components

moca-challenger includes 7 main goroutines: Monitor, Verifier, Vote Collector, Vote Broadcaster, Vote Collator, Tx Submitter, and Attest Monitor.
  • 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

Set your private key, deployment environment, and gas limit. The private_key and bls_private_key can be obtained as described in the next section. 
"moca_config": {
    "key_type": "local_private_key",
    "private_key": "your_challenger_private_key",
    "bls_private_key": "your_bls_private_key",
    "rpc_addrs": [ "https://testnet-lcd.mocachain.org" ],
    ...
},
"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://testnet-sp0.mocachain.org",
      ...
    ]
}

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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
Assuming you have a validator running, compile and start the process. 
make build
./build/moca-challenger --config-type local --config-path ./config/config.json

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Test and Verification

Create your own SP
The process is similar to creating a validator.
  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
Data recovery ensures that original data can be restored if lost on SPs.
  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.
When a challenge succeeds, the tampered data chunk file will be restored to the original file after a while.