"Hyperledger Indy provides tools, libraries, and reusable components for providing digital identities rooted on blockchains or other distributed ledgers so that they are interoperable across administrative domains, applications, and any other silo."
> "Byzantine fault tolerance is a sub-field of fault tolerance research inspired by the Byzantine Generals' Problem, which is a generalized version of the Two Generals' Problem."
* [Storage components](https://github.com/hyperledger/indy-plenum/blob/master/docs/storage.md) - As of now, RocksDB is used as a key-value database for all Storages.
* [indy-sdk](https://github.com/hyperledger/indy-sdk) - Everything needed to build applications that interact with an Indy distributed identity ledger.
* [indy-crypto](https://github.com/hyperledger/indy-crypto) - shared crypto library for Hyperledger Indy components. To be:
* [ursa](https://github.com/hyperledger/ursa) [[**ϟ**](https://www.hyperledger.org/blog/2018/12/04/welcome-hyperledger-ursa)][[**ϟ**](https://www.coindesk.com/hyperledger-launches-cryptography-toolbox-for-blockchain-developers)] "includes the Hyperledger Indy-Crypto code base that is the building block for anonymous credentials, the verifiable credentials protocol, in indy-sdk used by the Sovrin Network. [...] We are hopeful the shared library will help other platforms better incorporate and use ZKP-based credentials and leverage Sovrin for their identity component." (From Nathan George on Sovrin Telegram) [[**wiki**](https://wiki.hyperledger.org/projects/ursa)]