Privacy-Preserving Cross-Chain Order Book Protocol

Technical White Paper — Protocol Flow Details

Version 1.0 | 2026

1 Overview

Invisibook is a privacy-preserving cross-chain order book protocol designed for decentralized trading scenarios. It addresses a series of problems arising from the transparency of trade amounts in current DeFi order book models, including front-running, liquidity manipulation, other MEV attacks, and trading strategy leakage.

The core design philosophy of Invisibook is: prices are public, amounts are private. The on-chain order book exposes only price information for the matching engine to perform pairing, while the specific order amounts are stored on-chain as Poseidon hash commitments (Poseidon is tentatively chosen; other hash functions may be considered later — the key selection criterion is which hash achieves the best combined performance in MPC circuits and ZK proofs). No third party can learn the true size of any order. When two orders are successfully matched, the buyer and seller complete settlement through an off-chain peer-to-peer privacy settlement protocol, during which both parties’ order amounts remain confidential to outsiders at all times.

Chapter 1: Problem Background and Core Challenges

1.1 What Is Secret Addition

In secure multi-party computation (MPC), two parties (Alice and Bob) each hold a secret share of a binary number and wish to compute the sum of the two numbers without revealing the plaintext of either operand. Here, “secret share” refers to Boolean secret sharing: a bit x is split into two shares x₁ and x₂ such that x = x₁ ⊕ x₂, where ⊕ denotes the XOR operation. Alice holds x₁, Bob holds x₂, and each party’s share alone is a uniformly random bit from which the true value of x cannot be inferred.

Secure Multi-Party Computation (MPC) allows multiple participants to jointly compute a function without revealing their private inputs to each other. SPDZ is a widely used MPC protocol that not only protects privacy but also withstands malicious adversaries – even if some participants attempt to cheat or tamper with data, the protocol can detect such behavior and guarantee the correctness of the result. One of its key techniques is the information-theoretically secure Message Authentication Code (MAC) mechanism.

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