What is SegWit? Understanding Bitcoin’s segregated witness

In summary, Segregated Witness (SegWit) is a significant upgrade to the Bitcoin protocol that addresses issues related to transaction malleability and scalability. It works by separating witness data from transaction data, making transactions immutable once signed and increasing the number of transactions that can fit within a block. This leads to increased transaction throughput, lower fees, and improved security for complex transactions. Additionally, SegWit paved the way for future upgrades and innovations like the Lightning Network.

As a researcher investigating the intricacies of the cryptocurrency world, I’m excited to share with you an extensive exploration of SegWit – the Significant Software Upgrade for Bitcoin (BTC). Delve into its origins, functionality, and impact on the Bitcoin network.

Table of Contents

It’s essential for those engaged in the crypto world to keep up-to-date with the latest technological advancements, be it mining, trading, or simply being an enthusiast. Although it’s been around for a few years now, segregated witness (SegWit) is a significant innovation that merits attention.

In this piece, we’ll provide clarity on the query, “What exactly is SegWit?” By dissecting the underlying mechanism, elucidating its functionality, and discussing both advantages and disadvantages for Bitcoin’s blockchain network.

What is SegWit?

As a Bitcoin analyst, I’d explain that in 2015, I came across a proposal by Peter Wuille called SegWit (Segregated Witness), which aimed to address an issue known as transactional malleability. This problem allowed malicious actors to manipulate the unique identifier or digital signature of a cryptocurrency transaction before miners verified and recorded it on the blockchain. By implementing SegWit in August 2017, Bitcoin was able to mitigate this vulnerability, enhancing the overall security and reliability of transactions within the network.

By the way, the resolution not only improved Bitcoin’s scalability but also allowed the nodes composing the Bitcoin network, commonly referred to as computers, to adopt a novel transaction format.

As a crypto investor, I’ve witnessed firsthand the controversial implementation of SegWit in the Bitcoin community. While it brought undeniable advantages, such as increasing transaction throughput and reducing fees, it sparked fierce opposition. The crux of the issue was a clash between two factions – miners, who prioritized their profitability, and developers, whose main goal was to enhance Bitcoin’s speed and affordability.

The network experienced a significant point of conflict, leading to its initial user-initiated hard fork and setting off a series of occurrences that gave rise to multiple Bitcoin spin-offs such as Bitcoin Cash (BCH).

As a crypto investor, I can tell you that SegWit, or Segregated Witness, was a significant upgrade to Bitcoin’s core protocol. Instead of storing the entire signature and previous hash in every transaction, it only includes a reference (witness) to the signature and previous transaction. This change not only got rid of malleability issues but also enhanced Bitcoin’s scalability and efficiency by reducing the size of each transaction and allowing more transactions per block.

As an analyst studying Bitcoin transactions, I’ve noticed that historical transactions used to store all relevant information – sender and receiver details, as well as digital signatures or witness data – within the same block. With SegWit, this approach has been altered. Instead, witness data is now separated from transaction data, enabling more transactions to be accommodated in a single block.

Making alterations to a digital signature in a transaction proved extremely difficult and risked rendering dependent transactions invalid. Malicious actors could exploit this weakness, leading to fraudulent activities or disruptions within the blockchain system.

As a crypto investor, I can tell you that an upgrade was implemented on the Bitcoin blockchain, which expanded its block size limit. Consequently, this improvement allows the network to process a greater number of transactions each second, enhancing its overall efficiency.

How does SegWit work?

To effectively respond to the query “How does SegWit function?”, it’s essential to initially understand the composition of a Bitcoin transaction.

As touched on in the section above, Bitcoin transactions usually consist of two main components:

  • Transaction data: This includes the sender’s and recipient’s addresses, the amount users are sending, and other essential information.
  • Witness data: It consists of the digital signatures that verify the transaction’s validity.

As a researcher studying the Bitcoin protocol, I’ve discovered that prior to Segregated Witness (SegWit), transaction data and witness data were intermingled within each block. This configuration imposed limitations on block sizes and left the network susceptible to transaction malleability issues. To put it simply, having both types of data in one place created potential vulnerabilities for the network.

How did SegWit fix transaction malleability?

SegWit addressed the problem of transaction malleability by distinguishing between the parts of a transaction that are subject to modification and those that aren’t. In Bitcoin transactions, malleability can occur in two ways. Initially, after a transaction is signed, unscrupulous actors might add additional data to the script containing the signature and other unlocking information. Alternatively, they could manipulate the digital signature itself within the script.

Any modifications to the ScriptSig and its signatures, which are integral components of a transaction’s identifier, will result in a new transaction ID.

SegWit addressed this problem by transferring all data, such as signatures and public keys, from the ScriptSig section to a new segment in SegWit transactions called the witness. Consequently, the ScriptSig became fixed after signing, ensuring that the transaction ID remained unchanged and the entire transaction stayed valid.

How did SegWit increase the block size?

SegWit expanded the capacity of blocks by employing a novel measurement method known as block weight. With this approach, more transactions could be accommodated in each block without the need to explicitly raise the block size cap.

As a Bitcoin analyst, I’d explain it this way: Prior to SegWit, each Bitcoin block was restricted to accommodating only 1MB of data, resulting in approximately 1,650 transactions per block. Subsequently, the limiting factor shifted from block size to block weight, calculated in weight units, allowing a single block to contain up to 2,700 transactions.

What is SegWit used for?

Segregated witness provides several significant use cases to the Bitcoin network:

Addressing transaction instability: The main objective of SegWit was to remedy the transaction malleability issue in cryptocurrencies like Bitcoin, which enabled the alteration of transaction identifiers prior to confirmation, resulting in complications with monitoring and safeguarding transactions.

Previously mentioned, SegWit resolved this problem by relocating the signature information to a distinct segment of a transaction, which isn’t factored into the transaction ID computation. Consequently, transactions become unchangeable following signature.

“SegWit expands the block size limit as explained previously, enabling more transactions to be incorporated in a single block. Consequently, the network becomes capable of processing a larger number of transactions every second, enhancing Bitcoin’s capacity to manage heightened activity.”

Reducing transaction fees: Since Bitcoin miners can include more transactions in each block they validate, it means the supply of transaction space also increases, which can help lower the fees during periods of high demand.

“Facilitating the implementation of L2 technologies: SegWit opened the door to Bitcoin’s L2 offerings, like the Lightning Network, by tackling transaction malleability and boosting scalability. These innovations operate above the Bitcoin blockchain, enabling swifter and more affordable transactions, thereby increasing Bitcoin’s utility for everyday use.”

As a crypto investor, I can tell you that the implementation of SegWit (Segregated Witness) upgrade in Bitcoin’s network significantly enhanced its flexibility. This improvement made it simpler for developers to introduce future modifications and enhancements to the Bitcoin protocol. By creating a more modular transaction structure, we can add new features and optimizations without causing major disruptions to the network. Essentially, SegWit paved the way for a more adaptable and evolving Bitcoin infrastructure.

Improving security in Bitcoin: Addressing transaction malleability and optimizing transactions enhances the network’s resistance to diverse attack types and weaknesses.

Advantages and disadvantages of SegWit

Certainly, Although SegWit has delivered numerous advantages to the Bitcoin system, it hasn’t been free of criticisms and obstacles. Let’s examine the pros and cons.


As a crypto investor, I’ve noticed that SegWit is a solution that enhances the capacity of the Bitcoin network by accommodating more transactions in each block. This ultimately reduces network congestion and improves overall efficiency.

Users can typically pay less for transactions due to more effective utilization of block space, resulting in cost savings.

3. Enhanced Security: SegWit strengthens the security of Bitcoin transactions, especially for intricate deals involving numerous signatories, by getting rid of the issue of transaction malleability.

4. Preparing the foundation for advancements: SegWit serves as a base for upcoming protocol enhancements and advancements, including the Lightning Network, which strives to boost Bitcoin’s capacity for greater scalability and faster transactions.


As a researcher studying the adoption of SegWit in the Bitcoin network, I’ve observed that while its usage has expanded over the months, the initial uptake was sluggish. Several users and service providers, such as Bitcoin wallets, took their time to implement the necessary upgrades. Not all Bitcoin-related services, including wallets, have adopted SegWit modifications yet.

2. Complexity: The changes introduced by SegWit can be complex and require significant adjustments by developers and service providers.

3. Disagreement over segment sizes: The adoption of Segregated Witness (SegWit) in Bitcoin sparked controversy within the community. Some advocates argued that expanding the block size would be a simpler approach to addressing scalability concerns, instead of implementing SegWit. This disagreement led to the emergence of multiple hard forks, including Bitcoin Cash.

4. Reduced earnings for miners: The implementation of SegWit could diminish miner income due to lower transaction fees. Furthermore, participating in a sidechain that accommodates witness data may be perceived as an unnecessary burden by miners since it doesn’t generate any revenue.


In essence, Segregated Witness (SegWit) is a significant enhancement for Bitcoin, tackling major concerns such as transaction malleability and scalability. You may recall that I previously described how SegWit distinguishes witness data from transaction data. By doing so, it becomes possible to pack more transactions into each block, resulting in heightened transaction throughput and reduced fees.

The unintentional division of data led to an expansion of Bitcoin’s block size, which subsequently enhanced its scalability and productivity. Consequently, this advancement paved the way for the emergence of L2 networks on the Bitcoin blockchain.

Read More

2024-05-28 19:21