PQ-Fabric: A Permissioned Blockchain Secure from Both Classical and Quantum Attacks

Abstract

Hyperledger Fabric is a prominent and flexible proposal for a permissioned distributed ledger platform. It supports modular consensus protocols, which allows for selecting distinct trust models and performance/throughput trade-offs. On the other hand, access control and identity management intrinsically relies on credentials issued by a Certificate Authority of a Membership Service Provider (MSP). The default MSP implementation, instantiated by the means of the the Blockchain Cryptographic Service Provider interface (BCCSP), only handles standard classical PKI methods for authentication and digital signatures, accommodating basically RSA and ECDSA classical signatures. Also only one single signature scheme is assumed to be employed at a given MSP instantiation. This makes the credential-related functions highly attached to single classical standard primitives. Unfortunately, it is well known that RSA and ECDSA are vulnerable to quantum attacks and an ongoing post-quantum standardization process run by NIST aims to identify quantum-safe drop-in replacements for such cryptographic primitives in a few years. In this paper, we propose a redesign of the credential-management procedures and related specifications in order to incorporate hybrid digital signatures (i.e., protection against both classical and quantum attacks using two signature schemes) that include the quantum-safe signatures from the upcoming NIST standards. We also validate our proposal by providing an implementation of Fabric along with the Open Quantum Safe library. Our implementation employs the crypto-agility concept,which allows for plugging in different algorithms in the MSP Credentials and performing comparative benchmarks with them. Moreover, our proposal is backwards compatible with the client implementations, and no SDK changes would be required for the client Node.JS code.