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Segregated Witness , or SegWit , is the name used for an implemented soft fork change in the transaction format of the cryptocurrency bitcoin , which has also been implemented on currencies such as Litecoin , DigiByte , Vertcoin and Feathercoin. It does this by splitting the transaction into two segments, removing the unlocking signature "witness" data from the original portion and appending it as a separate structure at the end.
The original data segment would be counted normally, but the "witness" segment would, in effect, be counted as a quarter of its real size. Bitcoin is a cryptocurrency, a form of money using cryptography to keep transactions secure. This forms a chain of blocks, or a blockchain. Each block contains information about who sends and receives a given unit of bitcoin a transaction , as well as the signature that approves each transaction. Originally, there was no limit to the size of blocks. However, this allowed malicious actors to make up fake "block" data that was very long as a form of denial-of-service attack DoS attack.
These fake blocks would be detected, but doing so would take a very long time, slowing down the whole system. This way, attacks using huge blocks would be instantly detected and rejected, without significantly slowing down the network. A new block is added to the chain at random intervals averaging, by design, ten minutes proof-of-work causes this delay.
Together with the limit on block-size, this limits the number of transactions that can be processed in a given time. Some sites work around this problem using "off-chain payments", conducting transactions without waiting for confirmation by the Bitcoin.
Others have proposed changes to Bitcoin that would reform the blockchain format in a backward-incompatible way. This is not compatible with systems that do not upgrade. Another property of SegWit is "transaction malleability ". Many people consider this a flaw because a user can potentially change a transaction ID. This could lead to extra bitcoin being sent if a user claims they never received the bitcoin and the sender checks the original transaction ID to verify which would not exist on the block chain if the ID was changed.
SegWit proposes significant backward compatibility. It hides its increased block size by changing the definition of a block to be measured as one million "units" instead of bytes. The "witness" signature data would be separated from the Merkle tree record of who is sending or receiving the bitcoins.
The "witness" data is moved to the end, and each byte of it would only count as one quarter of a "unit". The overall effect would be changing the average block size to about 1. This means the existing Bitcoin protocol doesn't change, allowing it to work without as much upgrading of software.
It also addresses signature malleability, by moving signatures out of the transaction data, making them impossible to change. This makes Bitcoin safer to use with Lightning Network , a way to speed up small payments by bundling them and only writing to the blockchain at the beginning and end of their execution, which would be slightly risky while the malleability problem still exists.
Segregated Witness was activated on August 24, On 21 July bitcoin miners locked-in a software upgrade referred to as Bitcoin Improvement Proposal BIP 91, meaning that the Segregated Witness upgrade activated at block , On November 8, , the developers of SegWit2x announced that the hard fork planned for around November 16, was canceled due to a lack of consensus. From Wikipedia, the free encyclopedia. Retrieved 20 December A Beginners Crash Course! Retrieved 9 October Retrieved 29 June Retrieved 23 June Retrieved 13 Apr Retrieved 19 July Retrieved 18 July Retrieved 21 July Archived from the original on 1 December Retrieved 23 November Archived from the original on 17 November Segregated Witness Will Activate on Bitcoin".