We present a new framework for asynchronous permissioned blockchain with high performance and post-quantum security. The framework contains two quantum-secure asynchronous Byzantine fault tolerance (aBFT) protocols, SodsBC and SodsBC++. We leverage concurrent preprocessing to accelerate the preparation of three cryptographic objects for the repeated consensus procedure, including common random coins as the needed randomness, secret shares of symmetric encryption keys for censorship resilience, and nested hash values for external validation predicates. The key idea behind our design is that the concurrent preprocessing mechanism can be well-supported by the consensus process of blockchains. The consumed objects in a block have been generated and globally agreed upon in a previous block. All our preprocessed objects utilize proven or commonly believed to be post-quantum cryptographic tools to resist an adversary equipped with quantum computation capabilities. We evaluate our protocols and their competitors in AWS in a typical setting where, the number of participants is 100 and each block part has 20,000 transactions. The results show that SodsBC and SodsBC++ reduce the latency of two state-of-the-art but quantum-sensitive competitors Honeybadger and Dumbo by 53% and 6%, respectively.

SodsMPC is a quantum-safe smart contract system. SodsMPC permissioned servers (verification nodes) execute contracts by secure multi-party computation (MPC) protocols. MPC ensures the contract execution correctness while trivially keeping the data privacy. Moreover, SodsMPC accomplishes the contract business logic privacy while protecting the contract user anonymous identity simultaneously. We express the logic of a contract by a finite state machine (FSM). A state transition of the FSM is represented by a blind polynomial with secret-shared coefficients. When using MPC to compute this blind polynomial, the contract business logic privacy is obtained. These coefficients which control the logic are binary secret shares. We also propose a base conversion method among binary and integer secret shares by MPC. Our contract anonymity comes from the “mixing-then-contract” paradigm. The online phase of the SodsMPC mixing is a multiplication between a preprocessed permutation matrix and an input vector in the form of secret sharing, which accomplishes a fully randomized shuffle of the inputs and keeps the secret share form for the following contract execution. All SodsMPC components, including a verifiable secret sharing scheme, are quantum-safe, asynchronous, coping with t <; n/3 compromised servers, and robust (tolerates Byzantine servers) in both preprocessing and online phases.