hard fork [English]
No definition in earlier IP projects. ITrust definition not yet developed.
- Bitcoin Developer Glossary 2017 (†791 s.v. "hard fork"): A permanent divergence in the block chain, commonly occurs when non-upgraded nodes can’t validate blocks created by upgraded nodes that follow newer consensus rules.
- BlockchainHub Glossary (†807 s.v. "Hard Fork"): A hardfork is a change to the blockchain protocol that makes previously invalid blocks/transactions valid, and therefore requires all users to upgrade their clients. The most recent example of a hardfork in public blockchains is the Ethereum hardfork which happened on July 21st 2016. The hardfork changed the Ethereum protocol, therefore second blockchain emerged (Ethereum Classic, ETC) which supports the old Ethereum protocol. In order to continue existing ETC needs miners, which would validate the transactions on the blockchain.
- Scaling Bitcoin  (†845 s.v. "Hardfork"): A hardfork is a change to the bitcoin protocol that makes previously invalid blocks/transactions valid, and therefore requires all users to upgrade. Any alteration to bitcoin which changes the block structure (including block hash), difficulty rules, or increases the set of valid transactions is a hardfork.
- Amsel 2016 (†829 para.3): A hard fork suggested by EthCore will replace the previously immutable contract known as TheDAO and perhaps any other attacked contracts. It will also directly transfer ether from attacker contracts back to the original DAO. (†2163)
- Bitcoin Developer Glossary 2017 (†791 ): · Fork (a regular fork where all nodes follow the same consensus rules, so the fork is resolved once one chain has more proof of work than another) · Soft fork (a temporary divergence in the block chain caused by non-upgraded nodes not following new consensus rules) · Software fork (when one or more developers permanently develops a codebase separately from other developers) · Git fork (when one or more developers temporarily develops a codebase separately from other developers (†2025)
- Kar & Wong 2016 (†828 para.11): That leaves a hard fork, where the core developers of Ethereum unilaterally make the decision to essentially create a new version of the network with different rules than the original. Then, miners, exchanges, and other major apps that are built on it need to decide if they want to a part of the new version of Ethereum or the original. Hence, the idea of a fork. (†2162)
- Smith & Atlas 2016. (†830 s.v. "introduction" ): A hard consensus fork occurs when blocks that would have previously been considered invalid are now valid. Any Bitcoin user, miner, exchanger, etc. who wants to stay in consensus with the network must upgrade his software during a hard consensus fork; otherwise, some new block that the network accepts will appear as invalid to him. (†2165)