Please describe your proposed solution.
Threshold signatures are a cryptographic technique where a group of participants collaboratively create a signature without relying on a single individual's private key. It enhances security and resilience. Participants each hold a share of the private key and combine them to generate a valid signature. Threshold signatures offer distinct advantages over both single-key signatures and multi-signature scripts in the context of a blockchain application. A great introduction may be found in the Coinbase blog article on threshold signatures.
Compared to single-key signatures, threshold signatures enhance security and resilience. With a single key, if it is compromised or lost, the entire system's security is jeopardized. In contrast, threshold signatures distribute the signing authority among multiple participants, each holding a share of the private key. This means that even if some participants' key shares are compromised or unavailable, as long as the required threshold number of participants is active, a valid signature can still be generated. This significantly reduces the risk of a single point of failure and improves the overall security of the blockchain system.
Additionally, compared to multi-signature scripts, threshold signatures offer advantages in terms of efficiency and scalability. In a multi-signature scheme, each transaction input requires multiple signatures, resulting in larger and more complex transactions. In contrast, threshold signatures allow for a single aggregated signature to represent the combined authorization of multiple participants. This results in smaller blockchain transactions, reduces transaction fees, and improves the overall efficiency of the blockchain network.
By combining enhanced security and resilience with improved efficiency and scalability, threshold signatures provide a compelling solution for blockchain applications, addressing the limitations of both single-key signatures and multi-signature scripts. They offer increased security against key compromise and enable more streamlined and cost-effective transaction processing on the blockchain.
Threshold signatures can be implemented using the same underlying cryptographic algorithm as Cardano's default Ed25519 signatures. Ed25519 is a widely used and well-regarded elliptic curve algorithm known for its efficiency and security. Threshold signatures can be constructed using Ed25519 keys, making them compatible with the existing infrastructure of the Cardano blockchain. Moreover, the verification algorithm for threshold signatures remains the same as the standard Ed25519 signature verification algorithm. This compatibility simplifies the integration of threshold signatures into the Cardano ecosystem, allowing for enhanced security and resilience without requiring changes to the underlying verification mechanisms.
Our proposed solution involves implementing the necessary threshold signature tooling to generate signatures that are compatible with Cardano wallets. We will leverage the existing Ed25519 signature capabilities of our C++ library Viper25519. The Viper25519 toolset will be expanded to include the required functionalities for key splitting and generating valid signatures from a subset of keys (M of N sub-keys, where M is less than or equal to N). These threshold signatures will be verifiable using the standard Ed25519 signature verification, ensuring compatibility with the Cardano blockchain. To validate the functionality, we will create a CLI tool that can generate a split key, corresponding public key, payment address, and perform transaction building and signing. It's important to note that this tool will not include a secure messaging protocol for multiple users to combine signatures. The entire codebase will be open source.
How does your proposed solution address the challenge and what benefits will this bring to the Cardano ecosystem?
This project will provide product developers coming to the Cardano ecosystem with verified tooling and reference implementations upon which to build secure dApps and other integrations using threshold signature technology. Threshold signatures represent an advancement over multi-signature scripts when multi-factor authentication is desired for enhanced security. The availability of such tooling will make Cardano an attractive candidate to builders.
How do you intend to measure the success of your project?
Success for this project will be measured by the ability to showcase successful transactions on the Cardano testnet using a threshold signature wallet. A further metric will be potential follow on projects that will rely on the successful completion of the proposed tooling.
Please describe your plans to share the outputs and results of your project?
The project code will be open-source and available on the Viper Science Gitlab and Github pages. Details of the project will be documented in a blog post and shared via the Viper Science social media outlets.