If smart contracts are to model real-world business processes and interactions, they must be connected to that world. Oracles — whether software, hardware, or human — enable that connection. Hedera provides a number of features that uniquely enables smart contract oracles.

After a client submits a transaction to Hedera, the client may seek confirmation that the transaction was added to consensus state and also to perhaps retrieve information associated with that addition. As an example, if the transaction is a transfer of hbars for the purchase of a coffee, then the coffee shop will likely want confirmation that its account received the customer’s payment before pouring the brew.

Online gaming architectures have historically relied on an intermediary to facilitate the game play — running centralized servers to which users would connect in order to find opponents and then managing the game state (e.g. where all characters are in a Massively Multiplayer Online (MMO) game, or how much gold each has, or where the pieces are in chess).

Distributed Ledger Technologies (DLTs) commonly have simple and inflexible forms of immutability. Hedera supports a more flexible form of controlled mutability, which allows certain changes under certain circumstances, but prevents other types of changes. One area where this is particularly important is for smart contracts.

Some consensus algorithms are fragile — they cannot adapt to changes, either in the membership of nodes, or in the influence of those nodes towards consensus. The result is that such changes cause consensus to be prevented or corrupted. This can be a problem for some types of distributed ledgers, but it is not a problem for Hedera.

The highest security standard for consensus algorithms is known as Asynchronous Byzantine Fault Tolerance (ABFT). The hashgraph algorithm, as used in the Hedera public ledger, achieves this gold standard, with a mathematical proof that it is ABFT. This proof-of-stake consensus system was first proved to be ABFT in a rigorous math proof published in 2016. That proof has now been verified by computer in a formal verification completed by a Carnegie Mellon University professor — and we think it is important to explain what that means.

It’s a wonderful bit of irony that the Fiddler on the Roof character singing the above is named ‘Hodel’.