The fourth and, presumably, the last version of the soft fork Segregated Witness has been released in testnet mode. It includes a new opcode, aimed to increase the flexibility of bitcoin transactions.

New SegWit version has been published by Bitcoin Core developers Pieter Wuille (Core Tech engineer in Blockstream), Eric Lombrozo (co-CEO of Ciphrex) and Johnson Lau. One of the main innovations of the recent SegNet 4 making it different from its predecessors is a new bitcoin improvement protocol CheckSequenceVerify (CSV).

CSV allows users to block selected bitcoins for a specific period of time, resulting in that after this period the coins will be unlocked for transactions. The main difference of CSV protocol from another solution, called CheckLockTimeVerify (CLTV), is that the latter locks coins until a specified moment in time while CSV lock is relative and applies only after the transaction is included in a block. Thus, CSV implementation will provide greater flexibility in transactions and ability to create more advanced smart contracts.

“SegNet 4 offers a testing environment for routable bidirectional payment channels such as the Lightning Network or Amikopay,” Lombrozo told Bitcoin Magazine. “These projects could drastically increase Bitcoin's scalability, and allow for instant secure and cheap payments. With SegNet 4, we're providing a common network on which different projects can collaborate and test their ideas. It is open for anyone, and we're encouraging wallet developers to play around with it.”

The SegWit soft fork is expected to be released at some point in April, but, according to Lombrozo, the real launch time can be postponed for the sake of thorough testing.

“The original roadmap doesn't include specific dates,” Lombrozo added. “We're making a lot of progress, but we have a very rigorous testing and code review process which is necessary to ensure the Bitcoin network continues to operate safely and reliably.”

SegWit, in terms of the developers, is a “soft fork”. It means that after implementation, only miners would be required to undergo immediate software upgrade. All other users can join in whenever they want without any risk to be disconnected from the network. SegWit is also expected to temporarily solve the block size problem, freeing 1 MB of additional space within a block.

Elena Platonova