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zk-Agreements: A Privacy-Preserving Way to Establish Deterministic Trust in Confidential Agreements

To-Wen Liu, Matthew Green

TL;DR

zk-agreements presents a privacy-preserving framework that enables confidential but legally enforceable contracts by integrating zero-knowledge proofs, secure two-party computation, and smart contracts with trusted execution environments. The approach creates a verifiable off-chain evaluation flow and a cryptographic bridge from natural-language contracts to machine-executable rights and obligations using Accord Project tools. Key contributions include a privacy-preserving legal execution architecture, a verifiable off-chain evaluation pipeline, and a legal-cryptographic bridge for seamless integration with existing legal frameworks. This work addresses the essential trade-off between transparency and confidentiality in blockchain-based agreements and offers a practical path toward private, automated dispute resolution and enforcement.

Abstract

Digital transactions currently exceed trillions of dollars annually, yet traditional paper-based agreements remain a bottleneck for automation, enforceability, and dispute resolution. Natural language contracts introduce ambiguity, require manual processing, and lack computational verifiability, all of which hinder efficient digital commerce. Computable legal contracts, expressed in machine-readable formats, offer a potential solution by enabling automated execution and verification. Blockchain-based smart contracts further strengthen enforceability and accelerate dispute resolution; however, current implementations risk exposing sensitive agreement terms on public ledgers, raising serious privacy and competitive intelligence concerns that limit enterprise adoption. We introduce zk-agreements, a protocol designed to transition from paper-based trust to cryptographic trust while preserving confidentiality. Our design combines zero-knowledge proofs to protect private agreement terms, secure two-party computation to enable private compliance evaluation, and smart contracts to guarantee automated enforcement. Together, these components achieve both privacy preservation and computational enforceability, resolving the fundamental tension between transparency and confidentiality in blockchain-based agreements.

zk-Agreements: A Privacy-Preserving Way to Establish Deterministic Trust in Confidential Agreements

TL;DR

zk-agreements presents a privacy-preserving framework that enables confidential but legally enforceable contracts by integrating zero-knowledge proofs, secure two-party computation, and smart contracts with trusted execution environments. The approach creates a verifiable off-chain evaluation flow and a cryptographic bridge from natural-language contracts to machine-executable rights and obligations using Accord Project tools. Key contributions include a privacy-preserving legal execution architecture, a verifiable off-chain evaluation pipeline, and a legal-cryptographic bridge for seamless integration with existing legal frameworks. This work addresses the essential trade-off between transparency and confidentiality in blockchain-based agreements and offers a practical path toward private, automated dispute resolution and enforcement.

Abstract

Digital transactions currently exceed trillions of dollars annually, yet traditional paper-based agreements remain a bottleneck for automation, enforceability, and dispute resolution. Natural language contracts introduce ambiguity, require manual processing, and lack computational verifiability, all of which hinder efficient digital commerce. Computable legal contracts, expressed in machine-readable formats, offer a potential solution by enabling automated execution and verification. Blockchain-based smart contracts further strengthen enforceability and accelerate dispute resolution; however, current implementations risk exposing sensitive agreement terms on public ledgers, raising serious privacy and competitive intelligence concerns that limit enterprise adoption. We introduce zk-agreements, a protocol designed to transition from paper-based trust to cryptographic trust while preserving confidentiality. Our design combines zero-knowledge proofs to protect private agreement terms, secure two-party computation to enable private compliance evaluation, and smart contracts to guarantee automated enforcement. Together, these components achieve both privacy preservation and computational enforceability, resolving the fundamental tension between transparency and confidentiality in blockchain-based agreements.
Paper Structure (37 sections, 6 equations, 3 figures, 3 tables, 7 algorithms)

This paper contains 37 sections, 6 equations, 3 figures, 3 tables, 7 algorithms.

Table of Contents

  1. Introduction
  2. Our Contribution
  3. Related Works
  4. Preliminaries
  5. Zero-knowledge proofs.
  6. Computable legal contracts
  7. Trusted Execution Environment.
  8. Construction of zk-agreements
  9. Setups
  10. Trusted setup for zero-knowledge proofs. $(1^\lambda) \;\rightarrow\; (srs)$
  11. Computable Legal Contract Compilation. $(agr_{text}) \;\rightarrow\; (clc)$
  12. Key generation for participants. $(1^\lambda) \;\rightarrow\; (pk,sk)$
  13. Algorithms
  14. SignCLC $( sk_{buy}, sk_{sel}, clc) \rightarrow (clc_{signed})$.
  15. CommitCLC $(clc_{signed}, k) \rightarrow (h,\ clc_{comm})$.
  16. ...and 22 more sections

Figures (3)

  • Figure 1: PaymentUponDelivery contract
  • Figure 2: PaymentUponDelivery contract emitting a payment obligation.
  • Figure 3: Concerto data model for the PaymentUponDelivery contract.