What are sidechains and how do they work?

So what is a sidechain? Allow me to illustrate with an example.

What is one of the most frustrating experiences you are subjected to on a weekly basis?

For most it’s going to the supermarket, getting all your essentials and snacks and then going to the front of the store, only to find out that there are only two cash registers open – with endless lines of shoppers waiting at each.

The solution is easy right? Have more registers available to shoppers at peak times, right? RIGHT?!

That’s basically how sidechains work – the Ethereum and Bitcoin blockchain can only handle a certain amount of traffic at once, if that limit is reached the network and the processing of transactions slow down. So, sidechains allow some of the volume of activity to be done off the main chain.

Sidechains became a necessity as blockchains, their function and user base rapidly expand. Being able to add independent blockchains that are connected to the main chain by two-way bridge to offload activity when the main chain is overloaded, is invaluable. Because they are independent they also have their own consensus mechanism.

Key takeaways:

  • Sidechains are independent blockchains that are used to lower transaction processing time, when the main chain sees a lot of traffic
  • Sidechain are crucial to the smooth and efficient operation of the main chain
  • As independent blockchains they have their own consensus

What is a sidechain?

You may also see sidechains referred to as child chains and the main chain referred to as the parent chain.

Their primary purpose is to allow for the scalability of the parent chain, but they come with an interesting security perk. Because they are independent, working with their own mechanism for consensus, even if the child chain is compromised, the parent blockchain may remain unaffected.

So in essence a sidechain or child chains give the main blockchain scalability, flexibility, security and the ability to function more effectively.

How does a sidechain work?

The way a sidechain works on a main blockchain like Bitcoin is simple. Here’s a step by step list of the actions when a transaction is “off loaded” to non-primary blockchains.

Two-way peg

A sidechain is a separate blockchain that connects to a parent blockchain, also called the mainchain, through a two-way peg mechanism. This connection allows assets or data to move between the mainchain and the sidechain securely.

Locking assets

When assets are transferred from the mainchain to the sidechain; they are locked in a smart contract or similar mechanism on the mainchain to prevent double-spending.

Transaction validation

Transactions on the sidechain are validated by its own consensus mechanism, such as proof of stake or proof of work.


Once a transaction is validated on the sidechain, the corresponding assets are unlocked on the mainchain, making them available for use again.

Transferring assets back

Similarly, if assets need to be transferred from the sidechain back to the mainchain, a similar process is initiated, locking the assets on the sidechain and unlocking them on the mainchain.


Sidechains often implement additional security measures, such as cryptographic techniques and auditing protocols, to ensure the security of assets transferred between the mainchain and the sidechain.

Overall, sidechains extend the functionality of a blockchain network by enabling the creation of new features or applications while maintaining the security and integrity of the mainchain.

They are commonly used for testing new technologies, scalability solutions, or implementing specific functionalities for particular use cases.

Key components of sidechain technology

Two-way Pegs

In the context of sidechains, a two-way peg refers to the mechanism enabling secure transfer of assets or data between the mainchain and the sidechain. It involves locking assets on the mainchain, validating activity on the sidechain, and unlocking assets accordingly.

This two-way peg mechanism ensures integrity and prevents double spending, facilitating interoperability while maintaining security between the main blockchain and sidechain.

Smart contracts and federations

Smart contracts in sidechain technology automate tasks like asset locking and unlocking, transaction validation, and governance. They ensure security and integrity during asset transfers and network operations. Federations, trusted groups of nodes, contribute to consensus mechanisms, bolstering network security and governance.

Smart contracts and federations enable efficient, secure, and decentralised functionality within sidechain ecosystems, allowing interoperability with mainchains.

The benefits of sidechains

  1. Scalability: sidechains allow for the offloading of activity and computations from the mainchain, thus alleviating congestion and improving scalability. This enables the mainchain to focus on its primary functions while sidechains handle specific use cases or applications.
  2. Customisation and flexibility: sidechains can be customised to meet the specific requirements of different applications or use cases. Developers have the flexibility to tailor consensus mechanisms, governance structures, and features to suit their needs without affecting the mainchain’s operation.
  3. Interoperability: sidechains enable interoperability between different blockchain networks. Assets or data can be securely transferred between the mainchain and sidechain using two-way peg mechanisms, allowing for seamless integration and collaboration across disparate blockchain ecosystems.
  4. Experimental and testing environment: sidechains provide a sandbox environment for experimenting with new technologies, protocols, or features before deploying them on the mainchain. This allows developers to test scalability solutions, consensus algorithms, or smart contract functionalities without risking the stability or security of the mainchain.
  5. Specialised use cases: sidechains can cater to specialised use cases or applications that require specific features or functionalities. For example, a sidechain optimised for high-speed could be used for micropayments, while another sidechain focused on privacy features could be used for confidential transactions.
  6. Enhanced privacy: sidechains can implement privacy-enhancing techniques such as zero-knowledge proofs and keep confidentiality to provide enhanced privacy and anonymity for users. This is particularly useful for applications where privacy is a priority, such as healthcare or financial activity.
  7. Reduced transaction fees: by processing activity off-chain, sidechains can reduce transaction fees compared to executing transactions directly on the mainchain. This can make blockchain-based applications more cost-effective for users, particularly in scenarios with high transaction volumes.

Overall, sidechains offer advantages such as scalability, customisation, interoperability, experimental environments, specialised use cases, enhanced privacy, and reduced transaction fees, making them a valuable addition to the blockchain ecosystem for addressing diverse needs and requirements.

Risks and challenges of sidechains

Sidechains present promising solutions for enhancing blockchain scalability, customisation, and interoperability on many blockchains including the Bitcoin network since it adapted its latest protocol change to allow for smart Bitcoin contracts.

However, they also come with inherent risks and challenges. Security vulnerabilities may arise from the complexity of the two-way peg mechanism and smart contracts, leading to potential exploitation by malicious actors.

Centralisation concerns may emerge if sidechains heavily rely on a limited number of federated nodes for consensus, undermining decentralisation principles.

Achieving seamless interoperability between mainchains and sidechains can be complex due to protocol and governance incompatibilities. Additionally, regulatory compliance, economic incentives, liquidity, and adoption pose significant hurdles that must be addressed to ensure the success and sustainability of sidechain solutions.

Despite these challenges, with careful planning, robust security measures, and transparent governance, sidechains hold the potential to offer valuable advancements in the blockchain ecosystem.

Sidechains vs layer-2 solutions

Sidechains and layer-2 solutions both aim to address scalability issues in blockchain networks, but they differ in their approaches and implementations. Sidechains operate as separate blockchains that are pegged to the mainchain, allowing for the offloading of activity and computations to alleviate congestion and improve scalability.

They offer customisation and flexibility, enabling developers to tailor consensus mechanisms, governance structures, and features to meet specific requirements. However, sidechains may introduce security risks, centralisation concerns, and interoperability challenges, particularly when transferring assets or data between different blockchain networks. Despite these challenges, they provide sandbox environments for experimenting with new technologies and specialised use cases.

In contrast, layer-2 solutions seek to enhance scalability by building additional layers on top of existing blockchains, rather than creating separate blockchains like sidechains. These solutions, such as payment channels, state channels, and sidechain solutions, aim to process activity off-chain, reducing congestion on the mainchain and increasing transaction throughput.

Layer 2 solutions often offer greater interoperability with the mainchain since they operate within the same blockchain network, but they may also face challenges related to security, privacy, and trust in the underlying blockchain’s consensus. Overall, both sidechain and Layer 2 solutions play vital roles in addressing scalability challenges in blockchain networks, each with its unique advantages and trade-offs.

Navigating the future of sidechains

The future of sidechain solutions holds promise for unlocking new levels of scalability, interoperability, and customisation in the blockchain ecosystem. As technology advances, we can expect the technology to become more secure, efficient, and user-friendly, facilitating seamless asset transfers and data exchange between different blockchain networks. Innovations in consensus mechanisms, privacy-preserving techniques, and governance models will further enhance the functionality and reliability of the technology.

Additionally, sidechain technology may find widespread adoption across various industries, offering tailored solutions for specific use cases such as decentralised finance, supply chain management, and digital identity. Overall, the future of sidechain solutions is poised to drive greater innovation and efficiency in blockchain technology.


In conclusion, sidechains offer a promising avenue for enhancing scalability, interoperability, and customisation within the blockchain ecosystem. Analogous to additional cash registers in a supermarket alleviating long queues, sidechains enable the offloading of activity from mainchains, enhancing efficiency during peak times.

As independent networks tethered to mainchains, they not only provide scalability but also bolster security through separate consensus mechanisms. Despite challenges like interoperability issues and regulatory compliance, sidechains remain pivotal for fostering innovation and addressing diverse needs across industries. With ongoing advancements in technology and governance, the future of sidechains holds immense potential to drive further innovation and efficiency in blockchain technology.

FAQ: Frequently Asked Questions

What is a sidechain?

A sidechain is an independent network that has a two-way bridge to the main chain, allowing for increased scalability, flexibility and security.

What is the purpose of a sidechain?

The purpose of a sidechain is to direct activity off the main blockchain, either the Bitcoin network or other, to allow for faster processing and scalability.

What is an example of a sidechain?

The Liquid Network is a type of sidechain, that improves the functionality of Bitcoin transactions, as well as the distribution of digital assets, and exchanges.

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