Satoshi Nakamoto's Proof-of-Work (PoW) longest chain (LC) protocol was a breakthrough for Internet-scale open-participation consensus. Many Proof-of-Stake (PoS) variants of Nakamoto's protocol such as Ouroboros or Snow White aim to preserve the advantages of LC by mimicking PoW LC closely, while using PoS for Sybil resistance. Previous works have proven these PoS LC protocols secure assuming all network messages are delivered within a bounded delay. However, this assumption is not compatible with PoS when considering bandwidth constraints in the underlying communication network, because PoS enables the adversary to spam the network with equivocating blocks, which is impossible in PoW. The bandwidth constraint necessitates that nodes choose carefully which blocks to spend their limited download budget on. We show that `download along the longest header chain', a natural download rule for PoW LC, emulated by PoS variants, is insecure for PoS LC. Instead, we propose `download towards the freshest block' and prove that PoS LC with this download rule is secure in bandwidth-constrained networks. In experiments, we validate our claims and showcase the behavior of these download rules under attack. By composing multiple instances of our PoS LC protocol in parallel, we obtain a PoS consensus protocol with improved worst-case throughput, even in the presence of a spamming adversary. Our result can be viewed as a first step towards the co-design of consensus and network layer protocols.
翻译:中本科技长寿( PoW) 最长的连锁( LC) 协议是互联网规模开放参与共识的一个突破。 中本协议的许多测试( POS) 变体, 如 Oroboros 或 Snow White 等, 目的是通过密切模仿 PoW LC 来维护 LC 的优势, 同时使用 PoS 来抵抗 Sybil 。 以前的工作证明这些 PoS LC 协议保证了所有网络信息都是在受约束的延迟范围内发送的。 然而, 在考虑基础通信网络的带宽限制时,这一假设与POS 不符, 因为 PoS 使得对手能够用电子配置块对网络进行扫描。 在POW 协议中, 带宽限制要求节谨慎地选择哪些区块用于有限的平行下载预算。 我们显示, “ 沿着最长的页页链链链的自然下载规则 ”, PoWLC 的自然下载规则对于POS 步调不可靠。 相反, 我们提议“ 向最新鲜的通信区块装载”, 并证明, 连带网络的下载我们最坏的下载规则是安全的 。