Which Hyperledger project focuses on permissioned distributed ledger technology?

The choice of Fabric as the correct answer is based on its design and primary focus on permissioned distributed ledger technology. Hyperledger Fabric is a modular blockchain framework that enables enterprises to create and manage their own secure, scalable, and permissioned networks. This means that access to the network is controlled, and participants are authenticated before they can join the network or access its data.

Fabric allows organizations to tailor their blockchain solutions to specific needs by utilizing features such as smart contracts, known as chaincode, and configurable consensus protocols. Its architecture supports various identities, giving organizations the ability to manage permissions at multiple levels within the network, ensuring only authorized entities can access or modify data.

The other projects, while they contribute to the blockchain ecosystem, have different focuses. For example, Indy is specialized for decentralized identity solutions, Burrow serves as a smart contract platform with a focus on deterministic consensus, and Iroha caters to mobile application development. These differing objectives set apart Fabric's emphasis on permission and access control, making it the best example of a Hyperledger project centered on permissioned ledger technology.