Technology attributes
Segregated Witness (SegWit) is a blockchain protocol change that separates scripts and signatures into a new structure that is committed to blocks in the blockchain apart from other transaction data. This effectively compartmentalizes data that is needed to validate the blockchain state away from data that is necessary to actually determine the effects of transactions.
There are four main motivations for implementing SegWit on a blockchain protocol such as Bitcoin:
- Prevent nonintentional transaction malleability
- Improve the speed of transaction propagation
- Bypass existing blockchain constraints such as block size limitations in order to improve scalability
- Allow for the inclusion of data required for fraud proofs
Additionally, the transaction malleability fix allows for the creation of unconfirmed transaction dependency chains without counterparty risk, which is necessary in order to implement trustless layer 2 solutions such as the Lightning Network. SegWit itself is not necessary for the Lightning Network to work, but a transaction malleability fix of some kind is necessary. Other solutions for the malleability issue have been proposed such as Flexible Transactions.
SegWit first went live in a soft fork of the Bitcoin blockchain on August 23, 2017. A hard fork named SegWit2x that would force all miners to activate SegWit was scheduled for November 17, 2017. However, the fork was socially contentious and ultimately didn't garner enough support for the new cryptocurrency (B2X) to be relevant compared to BTC.
