Cryptology ePrint Archive: Report 2020/205

SodsBC: Stream of Distributed Secrets for Quantum-safe Blockchain

Shlomi Dolev and Ziyu Wang

Abstract: SodsBC is an efficient, quantum-safe, and asynchronous (when genesis coins are provided in a trust setup stage) blockchain utilizing only quantum-safe cryptographic tools and against at most $f$ malicious (aka Byzantine) participants, where the number of all participants $n=3f+1$. Our blockchain architecture follows the asynchronous secure multi-party computation (ASMPC) paradigm where honest participants agree on a consistent union of several block parts. Every participant proposes a block part, encrypted by a symmetric scheme, utilizing an efficient reliable broadcast protocol. The encryption key is distributed in the form of secret shares, and reconstructed after blockchain consensus. All broadcast instances are finalized by independent binary Byzantine agreement consuming continuously produced common random coins.

SodsBC continuously produces a stream of distributed secrets by asynchronous weak secret sharing batches accompanied by Merkle tree branches for future verification in the secret reconstruction. The finished secret shares are ordered in the same ASMPC architecture and combined to form common random coins. Interestingly, SodsBC achieves the blockchain consensus, while the blockchain simultaneously offers an agreement on available new coins. Fresh distributed secrets also provide SodsBC with forward secrecy. Secret leakage does not affect future blocks. The SodsBC cloud prototype outperforms centralized payment systems (e.g., VISA) and state of the art asynchronous blockchains.

Category / Keywords: cryptographic protocols / Efficient Blockchain Consensus, Secret sharing, Quantum-safe, Asynchronous, Forward secrecy

Date: received 18 Feb 2020, last revised 23 Jul 2020

Contact author: dolev at cs bgu ac il,ziyu@post bgu ac il,wangziyu@buaa edu cn

Available format(s): PDF | BibTeX Citation

Version: 20200723:073109 (All versions of this report)

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