Stateless and Secure Delivery versus Payment across Blockchains

We propose a secure, stateless and composable transaction scheme to establish delivery-versus-payment (DvP) across two (or more) blockchains without relying on time-locks, centralized escrow, or stateful intermediaries. The method minimizes coordination overhead and removes race conditions via a stateless decryption oracle that conditionally releases cryptographic keys. Specifically, the scheme requires: 1) a decryption oracle service (either centralized or using threshold decryption) that decrypts transaction-specific encrypted messages, and 2) a payment contract on the payment chain that executes conditional payments via transferAndDecrypt and emits the appropriate key, depending on transaction outcome (finality). The decrypted key then deterministically enables follow-up transactions - such as asset delivery or cancellation - on a separate blockchain. The protocol is lightweight and compatible with existing blockchain infrastructure (e.g., Ethereum), and avoids timeouts or pre-defined orderings. Our approach improves atomic cross-chain settlement and can serve as a blueprint for decentralized inter-chain financial markets. The protocol allows for multi-party DvP across multiple chains. A multi-party delivery versus payment is a valuable trade feature as it allows to bound multiple trade into a single atomic unit, effectively reducing liquidity requirements.