Hard Fork Combinators in Blockchain: Protocol Changes

The Hard Fork Combinator is a tool for combining protocols on the Cardano blockchain after a Hard Fork occurs.

What is Hard Fork Combinator?

The hardfork combiner (first developed by IOHK) is a tool for combining protocols on the Cardano blockchain after a hardfork occurs.

How does Hard Fork happen?

A hard fork typically occurs to introduce updates to the blockchain. It requires signatures of multiple participants and usually changes certain parameters of an existing protocol.

A hard fork is the splitting of a blockchain into two different protocols running in parallel with each other, in which the new blockchain loses the history of the previous one. Typically, hard forks result in some blockchain downtime, which disrupts transactions and user experience. Another way is to implement a hard fork on a live blockchain, which can disrupt the integrity of the blockchain. For example, the hard fork of bitcoin in 2017 led to the separation of the blockchain and the formation of Bitcoin Cash (BCH). This ultimately affected the interests of investors and traders.

However, IOHK has offered support for a hard fork combiner that effectively addresses both of these issues.

How does Hard Fork Combinator work?

Hard Fork Combinator is mostly used to merge protocols before and after an upgrade after a hard fork to eliminate the possibility of interrupts or restarts. When a hard fork occurs, it is almost impossible for all nodes to update to new parameters and block headers simultaneously and without interruptions. There is a need to put the blockchain into idle mode, and this causes anxiety for users.

As a solution to this dilemma, the IOHK Foundation came up with a hard fork combiner (HFC) for the Cardano blockchain (ADA) that allows multiple protocols to appear as one registry, so that all nodes do not need to update to a new blockchain simultaneously.

Cardano went from Byron (wallet-only protocols) to Shelley (proof-of-stake protocols) in July 2020, where a hard fork changed the functions and overall utility of the blockchain. At the time, there were more than 1 million wallets in the blockchain, and a failed hard fork would have meant the demise of Cardano and its funds.

The hard fork combiner was applied for the first time, and on July 29, 2020 at 21:45 UTC, the transition from Byron to Shelly was successful, with no downtime or errors. Users were informed but not restricted in their use, and the hard fork occurred in the background, allowing for a gradual transition of nodes over time. As of today, the Cardano blockchain combines the Byron and Shelley blocks. In future updates, the transition will also be supported by the hard fork combiner.

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