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Plenum Byzantine Fault Tolerant Protocol

Plenum is the heart of the distributed ledger technology inside Hyperledger Indy. As such, it provides features somewhat similar in scope to those found in Fabric. However, it is special-purposed for use in an identity system, whereas Fabric is general purpose.

Technical Overview of Indy Plenum

Refer to our documentation site at for the most current documentation and walkthroughs.

Please find the general overview of the system in Overview of the system.

Plenum's consensus protocol which is based on RBFT is described in consensus protocol diagram.

More documentation can be found in docs.

Other Documentation

  • Please have a look at aggregated documentation at indy-node-documentation which describes workflows and setup scripts common for both projects.

Indy Plenum Repository Structure

  • plenum:
    • the main codebase for plenum including Byzantine Fault Tolerant Protocol based on RBFT
  • common:
    • common and utility code
  • crypto:
    • basic crypto-related code (in particular, indy-crypto wrappers)
  • ledger:
    • Provides a simple, python-based, immutable, ordered log of transactions backed by a merkle tree.
    • This is an efficient way to generate verifiable proofs of presence and data consistency.
    • The scope of concerns here is fairly narrow; it is not a full-blown distributed ledger technology like Fabric, but simply the persistence mechanism that Plenum needs.
  • state:
    • state storage using python 3 version of Ethereum's Patricia Trie
  • stp:
    • secure transport abstraction
    • it has ZeroMQ implementations
  • storage:
    • key-value storage abstractions
    • contains leveldb implementation as the main key-valued storage used in Plenum (for ledger, state, etc.)


  • Plenum makes extensive use of coroutines and the async/await keywords in Python, and as such, requires Python version 3.5.0 or later.
  • Plenum also depends on libsodium, an awesome crypto library. These need to be installed separately.
  • Plenum uses ZeroMQ as a secure transport
  • indy-crypto
    • A shared crypto library
    • It's based on AMCL
    • In particular, it contains BLS multi-signature crypto needed for state proofs support in Indy.

Contact Us

  • Bugs, stories, and backlog for this codebase are managed in Hyperledger's Jira. Use project name INDY.
  • Join us on Jira's Rocket.Chat at #indy and/or #indy-node channels to discuss.

How to Contribute

How to Start Working with the Code

Please have a look at Dev Setup in indy-node repo. It contains common setup for both indy-plenum and indy-node.