Unicity: Predicates and Atomic Swaps

2026-06-01

AI Summary

This work addresses the challenge of enabling secure and programmable spending conditions without relying on consensus participants. To this end, we introduce, for the first time, a predicate mechanism into the Unicity model, extending token ownership to programmable spending predicates executed off-chain by dependent parties. This extension preserves the original system’s security guarantees while supporting off-chain smart contract functionality. Leveraging the unforgeability of predicate families, we construct a formally secure spending model and design a complementary off-chain execution architecture together with an atomic swap protocol. Our approach successfully realizes trustless atomic swaps, demonstrating the practical applicability of the proposed framework.

Abstract

We generalize Unicity token ownership to programmable spending conditions called predicates, enabling smart-contract like functionality executed off-chain directly by relying parties rather than by consensus participants. We prove that the security properties of the Unicity execution layer are preserved under reduction to predicate family unforgeability. To demonstrate the utility of the model, we show how to implement trustless atomic swaps by using predicates.

Problem

• Unicity
• predicates
• atomic swaps
• token ownership
• smart contracts

Innovation

• predicates
• off-chain execution
• atomic swaps
• Unicity
• unforgeability