Private postquantum blockchain minimizes onchain data for payments
Compact Shielded CSV: Post-Quantum, Private, Lightweight Client-Side Validation Blockchain
Cryptography and Security
Summary
Current blockchains that protect against quantum computing attacks become bulky and slow because they store a lot of cryptographic data directly on the blockchain. The authors propose Compact Shielded CSV, a way to keep the blockchain data very small by moving heavy cryptographic proofs off the chain. They introduce a new tool called the degriefer that lets the system control ownership and prevent double spending just by using hashes, so no on-chain signatures are needed. This makes digital payments more private, efficient, and ready for future quantum threats.
What this means in practice
- •For digital payment platform engineers: Create blockchain payment systems that reduce on-chain data while remaining secure against quantum computer attacks and preserving user privacy.
- •For secure messaging developers: Design privacy-focused transaction protocols that minimize on-chain overhead for confidential asset transfers using compact proofs.
Authors
Dragos I. Ilie, Uri Lee, Iain D. Stewart, Jonathan Zhu, Elliot Jones, William J. Knottenbelt
Abstract
We propose Compact Shielded CSV, a private client-side validation blockchain for peer-to-peer payments designed for the postquantum era. Upgrading existing blockchains to quantum-resistant cryptography substantially increases on-chain overhead. By keeping all large cryptographic artifacts off-chain, Compact Shielded CSV keeps a minimal on-chain footprint independent of the size of the underlying cryptographic proofs and signatures. For a single input transaction, the onchain footprint is just 3 hashes (3x32 bytes): a nullifier, a degriefer, and a commitment to the transaction. We introduce the degriefer - a novel mechanism that enforces ownership and prevents double-spending using only hash commitments, eliminating the need for on-chain signatures entirely. These properties make Compact Shielded CSV a promising foundation for private, scalable, post-quantum digital payments.