FAQ

• How is Holochain different from blockchain?
• How is Holochain more environmentally ethical than blockchain?
• How are data validated on Holochain?
• What happens to data when a node leaves the network?

---

How is Holochain different from blockchain?

Holochain and blockchain are built for fundamentally different use cases. Blockchain is relatively good for systems where it’s absolutely necessary to maintain global consensus. Holochain is much better than blockchain at anything that requires less than universal consensus (most things): It’s faster, more efficient, more scalable, adaptable, and extendable.

Long before blockchains were hash chains and hash trees. These structures can be used to ensure tamper-proof data integrity as progressive versions or additions to data are made. These kinds of hashes are often used as reference points to ensure data hasn't been messed with — like making sure you're getting the program you meant to download, not some virus in its place.

Instead of trying to manage global consensus for every change to a huge blockchain ledger, every participant has their own signed hash chain (countersigned for transactions involving others). After data is signed to local chains, it is shared to a DHT where every node runs the same validation rules (like blockchain nodes all run the same validation rules. If someone breaks those rules, the DHT rejects their data — their chain has forked away from the holochain.

The initial Bitcoin white paper introduced a blockchain as an architecture for decentralized production of a chain of digital currency transactions. This solved two problems (time/sequence of transactions, and randomizing who writes to the chain) with one main innovation of bundling transactions into blocks which somebody wins the prize of being able to commit to the chain if they solve a busywork problem faster than others.

Now Bitcoin and blockchain have pervaded people's consciousness and many perceive it as a solution for all sorts of decentralized applications. However, when the problems are framed slightly differently, there are much more efficient and elegant solutions (like holochains) which don't have the processing bottlenecks of global consensus, storage requirements of everyone having a FULL copy of all the data, or wasting so much electricity on busywork.

How is Holochain more environmentally ethical than blockchain?

Holochain removes the need for global consensus, and with it, the expenditure of massive amounts of electricity to synchronize millions of nodes about data that aren't even relevant to them.

There are two reasons Holochain is vastly more efficient than blockchain and more ethical green sense:

1. It eliminates the need for all nodes to be synchronized with each other in global consensus. Sharding is usually enabled on Holochain. This means that when two nodes make a transaction, each node saves a countersigned record of that transaction. Additionally, the transaction is published to the Distributed Hash Table (sent to and saved by some unpredictably random nodes that can be looked up later for retrieval). Sharding is configurable by app, and in some cases it's a good idea to turn it off. For example, imagine a distributed Slack-like team messaging app. With only 40-50 members, full synchronization would be worth the extra bandwidth requirement for the benefit of offline messages and reduced load times. But for most applications, global synchronization isn't really needed and sharding is kept on. Because of DHTs, and the sharding they enable, Holochain actually doesn't rely on the transfer of large amounts of redundant information, and uses vastly less bandwidth than blockchain.
2. There's no mining on Holochain. Blockchain's proof-of-work system provides a hefty incentive for thousands of people to spend the processing power of their CPUs and GPUs using up huge amounts of electricity on solving a meaningless cryptographic puzzle. Holochain doesn't have mining.

How are data validated on Holochain?

On Holochain, each node that receives a record of a transaction validates it against the shared application rules and gossips it to their peers. If the rules are broken, that transaction is rejected by the validator.

There is no overall, global "correctness" (or consensus) built in to Holochain. Instead, each node that receives a record of a transaction validates it against the shared application rules and gossips it to their peers. If the rules are broken, that transaction is rejected by the validator. If foul play is detected on a node's part (the node is either propagating or validating bad data) that node is blocked and a warning is sent to others. Here's an infographic describing this process. In summary, instead of a global consensus system, Holochain uses an accountability-based system with data validation by peers. Applying this to the example of 'Ourbnb', an imaginary distributed version ofAirbnb: The Ourbnb Holochain app would certainly be written with a rule, "don't rent your apartment to two parties at the same time." So the moment a user rents to two parties at the same time, nodes receiving that datum on the DHT attempt to validate it against the app rules, detect a collision, and reject it. Holochain's gossip protocol is designed to operate at a rate at which collisions will be detected nearly immediately by gossiping peers. And since Holochain doesn't have a coin built into it, it incentivizes users to cooperate and co-create. As a user, you don't need to trust the provider of the application you're using, only agree with the shared protocols that make up the application itself. Aside from being responsible for the maintenance and security of apps they provide, application providers on Holochain are not like traditional application providers today (think Facebook, Twitter, etc.). They don't host your data because your data is stored by you and a random subset of the users of the application.

What happens to data when a node leaves the network?

When people running Holochain apps turn off their device, they leave the network. What happens to their data and the data of other people they were storing? There are always enough nodes that hold a given piece of data in the network so as to prevent data loss when nodes leave. The DHT and Holochain gossip protocol are designed this way. Also, the redundancy factor of data on a given DHT is configurable so it can be fine-tuned for any purpose