The Unicity Execution Layer
2026-06-01 • Cryptography and Security
Cryptography and Security
AI summaryⓘ
The authors present the Unicity Execution Layer, a system that helps people make secure transactions without using a blockchain directly, while making sure no one spends the same token twice. They created a security model showing that only the real owner can spend or block a token, and the service managing transactions can't trace tokens back to users. To keep users' identities private, they designed special signature methods that let one secret generate many public keys that don't link to each other, reducing the complexity of managing multiple keys. This approach supports private and secure token transfers with less hassle.
Off-chain transactionsDouble-spendingDigital signaturesPublic key cryptographyToken ownershipPrivacyUnlinkabilityMulti-public-key signatureSecurity modelKey management
Authors
Ahto Buldas, Dirk Draheim, Mike Gault, Risto Laanoja, Vladimir Rogojin, Ahto Truu
Abstract
This paper introduces the Unicity Execution Layer, a modular component of the Unicity framework enabling secure off-chain transactions while maintaining trustless double-spending prevention. We present a formal security model where token ownership is represented by public keys and transfers require digital signatures. We prove three fundamental security properties: (1) no double-spending--each token state can be spent at most once, (2) no blocking--only the legitimate owner can prevent a token from being spent, and (3) service-side privacy--the Unicity Service cannot link transactions with the same token. The user-side privacy is addressed by introducing generalized multi-public-key signature schemes that allow one secret to generate multiple unlinkable public keys, and interactive and non-interactive concrete instantiations, enabling private transactions with stable public identity with minimal key management overhead.