Taking Bitcoin to the next level with ESSPI

Continuous innovation is what fuels the world of Disputable Computation. Here at Fairgate, we never stop looking for ways to optimize and improve the technology we are building to bring complex computation to Bitcoin. That’s why we are excited to present ESSPI (ECDSA/Schnorr Signed Program Input)—a new scheme that enhances how program inputs are signed and verified in BitVMX. This advancement significantly reduces storage costs and improves efficiency, making Bitcoin computation faster, cheaper, and more scalable and secure than ever before.

Understanding the Challenge

Bitcoin was designed as a secure and decentralized system to bring the basic functionality of money to the digital realm. However, as the demand for more complex use cases grew, researchers and developers started an innovation race to overcome Bitcoin’s original limitations and expand its capabilities.

Some of these original limitations were set by design, as a strategy to minimize the security exposure of the whole system. Bitcoin Script, the part of the system that acts as the main agent of programmability, is not Turing complete and, in particular, it lacks statefulness. These characteristics of the Bitcoin blockchain are what limits its capacity to go beyond the basic functionality of money.

Bitcoin’s reduced attack surface comes at the expense of very limited options to express complex conditions for the creation and flow of transactions within the system. In short, you can’t run native smart contracts in Bitcoin: money is the most complex - and only - use case that bitcoin was made to handle…However, at the end of 2023, things started to change with the advent of BitVM, BitVMX and the Disputable Computation paradigm.

The push to build more sophisticated use cases on Bitcoin resulted in an innovation race not seen in the Bitcoin community in many years. This fertile and contagious atmosphere gave birth to multiple teams driving multiple projects in the space of Disputable Computation, finally bringing smart contract capabilities to Bitcoin.

The need to run complex computations efficiently is the main challenge taken on by some of these hardcore community researchers. BitVMX, the most versatile and efficient framework tackling the problem of computation in Bitcoin, allows the execution of sophisticated programs but it has long struggled with the inefficiency of verifying the authenticity of program inputs.

Traditionally, BitVMX relied on one-time signature (OTS) schemes such as Lamport and Winternitz to sign inputs. While secure, these methods required excessive storage—about 200 witness bytes per signed byte—making them impractical for many real-world use cases. This inefficiency limited Bitcoin’s potential as a computational platform.

Additionally, verifying data authenticity and availability within Bitcoin’s constraints has been an ongoing challenge. Many existing methods require large amounts of data to be stored on-chain, increasing economic costs and reducing efficiency. Finding a way to securely sign and verify program inputs while maintaining scalability was a crucial step forward.

Introducing ESSPI: A Smarter Solution

ESSPI solves this problem by replacing outdated signature schemes with industry-standard ECDSA and Schnorr signatures—the same cryptographic standards already used in Bitcoin transactions. This upgrade achieves a 1:1 storage ratio, a significant improvement over the previous 1:200 ratio, reducing costs and increasing scalability.

To accomplish this, ESSPI introduces three key innovations:

1. A New Hashing Core – The BitVMX CPU now includes a specialized hashing component that efficiently verifies program inputs without excessive storage requirements.
2. Partition-Based Fraud Detection in Hashing – ESSPI prevents fraud while hashing with a partition-based search mechanism, allowing the system to quickly identify and challenge incorrect hashing computations. This ensures that invalid inputs are detected.
3. Data Availability Proofs – ESSPI ensures that required data remains accessible using a new Timelock-Based DA (forcing data publication before a dispute begins). This new approach guarantees that program inputs are accessible.

Why ESSPI Matters

With ESSPI, BitVMX can now efficiently verify advanced cryptographic proofs such as SPV proofs, NiPoPoWs, and STARKs, bringing improvements and new possibilities to the Bitcoin ecosystem, including:

• Trustless blockchain bridges – More efficient cross-chain transaction verification, allowing Bitcoin to interact seamlessly with other blockchains.
• Optimized smart contracts – Allowing more complex logic without unnecessary overhead, expanding Bitcoin’s capabilities beyond simple transactions.
• Improved decentralized applications (dApps) – Supporting more powerful applications on Bitcoin, increasing its potential as a decentralized computing platform.
• Scalable verification of large computations – By reducing the storage burden, ESSPI enables Bitcoin to process and verify much larger computations, paving the way for new innovations in decentralized finance and beyond.

A Step Toward the Future of Bitcoin Computing

ESSPI represents a major milestone in making Bitcoin a robust platform for decentralized computation. By improving efficiency, security, and scalability, we are pushing Bitcoin closer to its full potential.

As more developers and organizations adopt Disputable Computation technologies, including BitVMX and ESSPI, the possibilities for Bitcoin will continue to expand, unlocking new opportunities in finance, gaming, and decentralized governance among many other sectors and industries.

At Fairgate, we believe in open-source innovation. We invite developers, researchers, and businesses to explore this breakthrough and help shape the future of Bitcoin computing.

To learn more about ESSPI, visit https://bitvmx.org

— Jonatan Altszul, CEO of Fairgate.