Unicity: Predicates and Atomic Swaps
2026-06-01 • Cryptography and Security
Cryptography and Security
AI summaryⓘ
The authors extend a system called Unicity that manages token ownership by allowing more flexible rules for spending tokens, called predicates. These predicates act like smart contracts but run off the main blockchain, handled by users instead of the whole network. They prove that their approach keeps the system secure by linking its safety to how hard it is to fake the predicate rules. To show this works, the authors explain how to use predicates to safely trade tokens between parties without needing to trust each other.
Unicity token ownershippredicate (programmable spending conditions)smart contractsoff-chain executionsecurity reductionpredicate family unforgeabilityatomic swapstrustless transactionsconsensusexecution layer
Authors
Ahto Buldas, Dirk Draheim, Mike Gault, Risto Laanoja, Vladimir Rogojin, Ahto Truu
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.