SegWit is the process by which the block size limit on a blockchain is increased by removing signature data from Bitcoin transactions. When certain parts of a transaction are removed, this frees up space or capacity to add more transactions to the chain. Segregate means to separate, and Witnesses are the transaction signatures. Hence, Segregated Witness, in short, means to separate transaction signatures. The concept of SegWit was formulated by bitcoin developer Pieter Wuille.
What Exactly Does SegWit Solve?
In short, the scalability problem of Bitcoin. The problem that the Bitcoin platform is facing is that as more and more transactions are being conducted, more blocks have to be added to the chain. Blocks are generated every 10 minutes and are constrained to a maximum size of 1 megabyte (MB). Due to this constraint, only a certain number of transactions can be added to a block. The weight of the transactions, represented by the blocks, is weighing down the network and causing delays in processing and verifying transactions, in some cases, taking hours to confirm a transaction as valid. Imagine all Bitcoin transactions that have been carried out since the inception of Bitcoin in 2009 sitting on the blockchain and still piling up. Long term, the system would not be sustainable if a radical change is not made.
Pieter Wuille’s Ingenious Solution
Dr. Pieter Wuille suggests that to solve this problem, the digital signature needs to be segregated from the transactions data. This process is known as Segregated Witness or SegWit. Digital signature accounts for 65% of the space in a given transaction. SegWit attempts to ignore the data attached to a signature by stripping off the signature from within the input and moving it to a structure towards the end of a transaction. This would increase the 1 MB limit for block sizes to a little under 4 MB.
In addition to slightly increasing the capacity size of blocks, SegWit also solves the problem where a receiver could intercept and modify the sender’s transaction ID in a bid to get more coins from the sender. Since the digital signature would be detached from the input, the unscrupulous party would have no way of changing the transaction ID without also nullifying the digital signature.
The Current State of SegWit
In August 2017, Bitcoin finally integrated SegWit into its system. SegWit is called a “soft fork” which means it is compatible with Bitcoin’s old code, minimalizing the hassle to make SegWit work. A hard fork, in contrast, is a system that is so totally incompatible with the old that a separate blockchain and currency is needed to make it work. In SegWit’s case, all the system needed was 95 percent of Bitcoin miners to accept the changes, which happened in less than a year.
In 2017, Bitcoin came out with a controversial hard fork SegWit 2x which increased block sizes from 1 MB to 2 MB. Most of the crypto community resisted SegWit 2x due to its ambitious changes. Consequently, the hard fork was canceled only a week before it was scheduled to occur.
Problems with SegWit
Miners and mining pool operators dislike SegWit. Transactions that go through Lightning Network are in a separate channel (i.e., the parallel “line”), which means these transaction fees will not flow to miners. Some Bitcoin services – like Bitcoin wallets – have been slow to support the SegWit changes. In February 2018, only 14% of Bitcoin transactions were made using SegWit Bitcoin. The numbers have improved since then, but the network is still in the woods.
Critics complain that SegWit doesn’t go far enough to solve the scalability problem. They maintain that only major changes to the Bitcoin platform and to the way Bitcoin handles transactions can decongest transaction flow.