Multi-Path Secret Sharing for QKD Key Relay in IP Networks

Trusted relay is currently the most practical deployment model for Quantum Key Distribution (QKD) networks. However, trusted relay nodes pose inherent security vulnerabilities, as intermediate nodes can access the plaintext random number used to derive the end-to-end QKD key, leading to complete key exposure if any single relay node is compromised. To mitigate this risk, this document proposes a Multi- Path Secret Sharing (MPSS) mechanism for QKD key relay. The core idea is to split the random number into multiple shares using a threshold secret sharing scheme, distribute each share through independent QKD relay paths planned by the Key Management Plane (KMP), and reconstruct the complete random number only at the destination node. This mechanism transforms the security model from "all-or-nothing" to "threshold security". Notably, this mechanism leverages an extended IPv6 Destination Option Header (DOH) to carry key share-related metadata and utilizes Segment Routing over IPv6 (SRv6) to enforce strict path isolation.