HSS-CoFHE

HSS-CoFHE (Homomorphic Secret Sharing with Collaborative Fully Homomorphic Encryption) enables zero-knowledge proving over secret-shared data. No single validator ever observes plaintext transactions. The production system achieves 3,506× speedup over classical FHE approaches through a noise-free protocol design with UC-composable security.

core design

Core Design

HSS-CoFHE splits transaction data across multiple proving servers so that no single server ever sees plaintext. Computation proceeds over encrypted and secret-shared values. The protocol converts encrypted data into additive secret shares without revealing the underlying values, then uses these shares for efficient ZK proof generation. The production protocol is noise-free (no accumulated encryption noise) and achieves UC-composable security — meaning it remains secure when composed with any other protocol.

collaborative proving

Collaborative Proving (VeriCoop)

VeriCoop is Ring0's collaborative proving protocol that generates ZK proofs over secret-shared data through a multi-phase process.

• Setup: Distribute correlation seeds to all proving servers
• Input sharing: Convert encrypted transaction data into secret shares — each server holds only a random-looking fragment
• Proof computation: Servers jointly compute the ZK proof over their shares using pre-generated correlations
• Privacy masking: Two-layer masking ensures the proof reveals nothing beyond its validity
• Output: Reconstruct the final proof from server contributions — the proof is public, but no server ever held the full witness

performance advantage

3,506× Performance Advantage

The production protocol achieves a multiplication gate cost of 3.2μs — a 3,506× speedup over the initial protocol design. This dramatic improvement comes from eliminating encryption noise entirely, which removes the need for expensive noise management operations. The result is that privacy-preserving proving is fast enough for real-time transaction processing.

threshold decryption

Threshold Decryption

HSS-CoFHE uses threshold decryption where a minimum number of servers (t out of n) must cooperate to decrypt any value. Corrupting fewer than t servers reveals absolutely nothing about the plaintext data — this is an information-theoretic guarantee, not a computational one. The threshold can be configured per deployment to balance between liveness (fewer servers needed) and security (more servers needed to collude).

uc security

UC-Composable Security

The protocol achieves Universal Composability (UC) security — the strongest standard for cryptographic protocols. UC-composable security means the protocol remains secure when run alongside any other protocols, in any scheduling environment, and under any composition. This is essential for a blockchain where HSS-CoFHE must compose safely with the ZK proving system, consensus mechanism, and networking layer simultaneously.