ARPA Network


The ARPA BLS Threshold Signature Scheme (BLS-TSS) Network is a cutting-edge decentralized cryptographic system designed to perform BLS threshold signature tasks. Randcast, our first product leveraging the ARPA Network, provides secure and reliable random number generation on multiple prevailing blockchains. Random number generation is a fundamental cryptographic primitive that plays a crucial role in various applications, including secure communications, encryption, gaming, and lotteries. By employing the principles of threshold cryptography, specifically using the Boneh–Lynn–Shacham (BLS) threshold signature scheme, the ARPA BLS-TSS Network pioneers a novel approach to produce random numbers in a distributed and tamper-resistant manner, thereby enhancing security and trust.

Core Architecture and Standards

The ARPA BLS-TSS Network follows a set of core standards that define its architecture and interactions, providing a solid foundation for its operation. Within the network, various nodes participate in the Distributed Key Generation (DKG) process — a critical step that lays the groundwork for generating threshold signatures. The DKG process results in the creation of a group public key and individual partial keys for each member in group. These cryptographic components are then used to produce random numbers in a distributed manner, ensuring that no single entity can control or manipulate the outcome.

The network is facilitated by a set of sophisticated smart contracts, with each one serving a specific role while working together harmoniously:

  • The NodeRegistry contract is the registration center of nodes, responsible for managing different node access methods, providing operations such as registering, activating, exiting, and slashing.

  • The Controller contract serves as the central authority for coordinating and managing the DKG process. It is responsible for node grouping strategy, and handles the execution of DKG-related operations, and the management of group-related information.

  • The Coordinator contract is the gateway that facilitates the interaction between the system's participants and the network during the DKG process. It manages phases in each particular DKG process.

  • The Adapter contract is the linchpin that manages the interaction between the Randcast protocol and the threshold signature-based random number generation mechanism. It is responsible for subscription management, task assignment, payment calculation and callback calling. It ensures that the randomness results are provided securely and reliably.

In addition, we provide utilities for interacting with the ARPA network, such as the RandcastSDK library, which provides essential tools for processing random numbers and performing operations that require randomness.

Key Concepts

  • Node: A node is the basic entity that forms the ARPA Network. It registers, be grouped, signs and aggregates the BLS signature, and commits the signature to the Adapter contract.

  • Group: A group is a set of nodes that are grouped together to listen to the signing request and generate BLS signatures. When a member joins or leaves, the group will be reconfigured.

  • DKG Process: A DKG process is the process of forming a group. It is initiated by the grouping strategy of the Controller contract and coordinated by the Coordinator contract. Nodes listen to the Controller contract and participate in the DKG protocol. After up to 4 phases, the participants will commit the result to the Controller contract.

  • BLS Process: A BLS process is the process of generating a BLS signature. It is initiated by the task assignment strategy of the Adapter contract. Nodes listen to the Adapter contract, then sign and send the partial signature to the committer nodes in the group. Upon receiving enough partial signatures, the committer nodes will aggregate and commit the aggregated BLS signature to the Adapter contract.


Overall, the ARPA BLS-TSS Network is a robust and innovative system that leverages the power of threshold cryptography and blockchain technology to provide superior decentralized random number generation, setting a new standard in the field.

By adhering to well-defined standards and utilizing a set of carefully designed smart contracts and libraries, the ARPA BLS-TSS Network ensures the integrity, security, and reliability of random number generation in a distributed environment.

Whether it's securing cryptographic protocols, enhancing online gaming experiences, or fortifying cryptographic key generation, the ARPA BLS-TSS Network brings a new level of trust and assurance to the world of randomness.

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