The Modular Indexer, which includes Committee Indexer and Light Indexer, introduces a fully user-verified execution layer for Bitcoin's meta-protocols. By leveraging the immutable and decentralized characteristics of Bitcoin, it provides a Turing-complete execution layer, going beyond the limitations of Bitcoin's script language.

Our innovative approach uses Verkle trees for trusted, decentralized data integrity. Even with a majority of hostile modular-indexer-committees, the Modular Indexer reliably connects Bitcoin with complex applications like BRC-20, propelling the ecosystem forward.

For a detailed understanding, refer to our paper: "Modular Indexer: Fully User-Verified Execution Layer for Meta-protocols on Bitcoin".

Stay updated on the latest progress in our L1F Discourse Group.

Committee indexer serves as a key component of Modular Indexer, and is responsible for reading each block of Bitcoin, calculating protocol states, and summarizing these states as a polynomial commitment namely checkpoint. Whenever the committee indexer obtains a new Bitcoin block, it generates a new checkpoint for the protocol and publishes it to the data availability layer for users to access. It is permissionless; anyone can operate his/her committee indexer for a given meta-protocol.

• Support Self-Mint and Burn logic for the BRC-20 meta-protocol and update to handle transactions with 5-byte ticks efficiently.
• Update reliance on OPI to version 0.4.1.
• Enable specifying the path to config.json via the command line.
• Remove Name field from config.json and allow it to be passed via the command line.

Before we stepped into the installation, ensure your machine is equipped with the minimum requirements: (We will optimize the Memory Usage soon)

We highly appreciate you running the committee indexer to contribute to the decentralization.

Committee indexer is built with Golang. You can run your own one by following the procedure below. Go version 1.22.0 is required for running repository. Please visit Golang download Page to get latest Golang installed.

Golang is easy to install all dependence. Fetch all required package by simply running.

go mod tidy

Modular Indexer relies on a running OPI indexer 0.4.1. First, clone the repository to get the necessary files:

# Clone the OPI repository
git clone https://github.com/bestinslot-xyz/OPI.git

Run this command to set up it up after indexing API to latest block:

cd OPI/modules/main_index
node index.js

cp config.example.json config.json
# Tailor config.json according to your setup

See Details of how to set up your own config.json.

go build

# Run the committee indexer with providing service
./modular-indexer-committee --cfg ./path/to/your/config.json --name "YourServiceName" --url "YourServiceURL" --protocol "meta-protocol" --committee --service

# Run the committee indexer in test mode
./modular-indexer-committee --cfg ./path/to/your/config.json --name "YourServiceName" --committee --service -t --blockheight 780010

Below are the explanation for each of the command flags.

• --cfg: Specify the path of your configuration file. This can be used to point the indexer to a specific configuration file instead of the default config.json.

• --name (-n): Indicate the name of the committee indexer service. This is useful for identifying different instances or configurations of the indexer.

• --url (-u): Indicate the url of the committee indexer service. Usually this prameter is the public IP address or the domain name of your machine.

• --protocol: Indicate the meta protocol supported by the committee indexer. Currently, only BRC-20 is supported by committee indexer. Please name it as brc-20 by default.

• --committee: This flag activates the committee functionality. When enabled, the committee indexer will publish checkpoints to the DA layer/S3.

• --service (-s): Use this flag to activate web service from committee indexer. When enabled, the committee indexer will provide web service for incoming query.

• --cache: By default, the state root cache is enabled, facilitating efficient verkle tree storage. This flag ensures that the application starts with the cache service activated, and will therefore fasten the initialization speed next time.

• --test (-t): Enable this flag to activate test mode, allowing the committee indexer to operate up to a specified block height limit. This mode is useful for development and testing by simulating the committee indexer's behavior without catching up to the real latest block.

• --blockheight: When test mode is enabled with -t, this flag sets a fixed maximum block height limit for the committee indexer's operations. It allows for focused testing and performance tuning by limiting the range of blocks the committee indexer processes.

https://docs.nubit.org/modular-indexer/nubit-committee-indexer-apis

Proper configuration of config.json is key for the smooth operation of the Committee Indexer.

The database section requires connection details to the OPI database. If you're running an OPI full node, ensure to provide the correct details as follows:

• host: The IP address or hostname of the machine where database is running.
• user: The username for accessing the database.
• password: The password associated with the above user account.
• dbname: The name of the database you're connecting to.
• port: The port number on which your database service is listening.

Define where and how to store the checkpoints generated by your committee indexer. The report section currently supports AWS S3 and the Data Availability (DA) layer.

• method: Choose between DA and S3 for publishing method.
• timeout: Timeout setting in milliseconds for publishing checkpoints.

DA Configuration:

• network: Specify the network (current: 'Pre-Alpha Testnet').
• namespaceID: Your designated namespace identifier. Leave it to empty to create a namespace following the instruction.
• gasCoupon: Custom code for managing transaction fees.
• privateKey: Your private key for secure transactions.

S3 Configuration:

• region: Specify the AWS S3 region for publishing.
• bucket: Name of the S3 bucket where checkpoints are stored.
• accessKey: Your AWS access key ID.
• secretKey: Your AWS secret access key.

The service section specifies the details of your API service, enabling access to the Committee Indexer functionalities.

• url: The URL where your API service is hosted and accessible.
• metaProtocol: Specify the meta-protocol served by your committee indexer (default 'brc-20').

🕸️ https://www.nubit.org 🪲 https://github.com/RiemaLabs/modular-indexer-committee/issues 📖 https://docs.nubit.org/developer-guides/introduction

• Is there a consensus mechanism among committee indexers?
  • No, within the committee indexer, only one honest committee indexer needs to be available in the network to satisfy the 1-of-N trust assumption, allowing the light indexer to detect checkpoint inconsistencies and thus proceed with the verification process.
• How is the set of committee indexers determined?
  • committee indexers must publish checkpoints to the DA Layer for access by other participants. Users can maintain their list of committee indexers. Since the user's light indexer can verify the correctness of checkpoints, attackers can be removed from the committee indexer set upon detection of malicious behavior; the judgment of malicious behavior is not based on a 51% vote but on a challenge-proof mechanism. Even if the vast majority of committee indexers are malicious, if there is one honest committee indexer, the correct checkpoint can be calculated/verified, allowing the service to continue.
• Why do users need to verify data through checkpoints instead of looking at the simple majority of the indexer network?
  • This would lead to Sybil attacks: joining the indexer network is permissionless, without a staking model or proof of work, so the economic cost of setting up an indexer attacker cluster is very low, requiring only the cost of server resources. This allows attackers to achieve a simple majority at a low economic cost; even by introducing historical reputation proof, without a slashing mechanism, attackers can still achieve a 51% attack at a very low cost.
• Why are there no attacks like double-spending in the Modular Indexer architecture?
  • Bitcoin itself provides transaction ordering and finality for meta-protocols (such as BRC-20). It is only necessary to ensure the correctness of the indexer's state transition rules and execution to avoid double-spending attacks (there might be block reorganizations, but indexers can correctly handle them).
• Why upload checkpoints to the DA Layer instead of a centralized server or Bitcoin?
  • For a centralized server, if checkpoints are stored on a centralized network, the service loses availability in the event of downtime, and there is also the situation where the centralized server withholds checkpoints submitted by honest indexers, invalidating the 1-of-N trust assumption.
  • For indexers, checkpoints are frequently updated, time-sensitive data:
    • The state of the Indexer updates with block height and block hash, leading to frequent updates of checkpoints (~10 minutes).
    • The cost of publishing data on Bitcoin in terms of transaction fees is very high.
    • The data throughput demand for hundreds or even thousands of meta-protocol indexers storing checkpoints is huge, and the throughput of Bitcoin cannot support it.
• What are the mainstream meta-protocols on Bitcoin currently?
  • The mainstream meta-protocols are all based on the Ordinals protocol, which allows users to store raw data on Bitcoin. BRC-20, Bitmap, SatsNames, etc., are mainstream meta-protocols. More meta-protocols and information can be found here
• What kind of ecosystem support has this proposal received?
  • The proposal is put forward by Nubit as a long-term supporter and builder of the Bitcoin ecosystem. We have also exchanged ideas with many ecosystem partners and hope to jointly promote the progress and improvement of the modular indexer architecture.