> "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)]