Coded blockchains have acquired prominence as a promising solution to reduce storage costs and facilitate scalability. Within this class, Luby Transform (LT) coded blockchains are an appealing choice for scalability owing to the availability of a wide range of low-complexity decoders. In the first part of this work, we identify that traditional LT decoders like Belief Propagation and On-the-Fly Gaussian Elimination may not be optimal for heterogeneous networks with nodes that have varying computational and download capabilities. To address this, we introduce a family of hybrid decoders for LT codes and propose optimal operating regimes for them to recover the blockchain at the lowest decoding cost. While LT coded blockchain architecture has been studied from the aspects of storage savings and scalability, not much is known in terms of its security vulnerabilities. Pointing at this research gap, in the second part, we present novel denial-of-service threats on LT coded blockchains that target nodes with specific decoding capabilities, preventing them from joining the network. Our proposed threats are non-oblivious in nature, wherein adversaries gain access to the archived blocks, and choose to execute their attack on a subset of them based on underlying coding scheme. We show that our optimized threats can achieve the same level of damage as that of blind attacks, however, with limited amount of resources. Overall, this is the first work of its kind that opens up new questions on designing coded blockchains to jointly provide storage savings, scalability and also resilience to optimized threats.

翻译：编码区块链作为一种降低存储成本并促进可扩展性的有前景的解决方案，已获得广泛关注。在此类方案中，Luby Transform (LT) 编码区块链因其拥有多种低复杂度解码器而成为实现可扩展性的一个吸引人的选择。在本工作的第一部分，我们指出传统的LT解码器（如置信传播和即时高斯消元法）对于具有不同计算和下载能力的节点的异构网络可能并非最优。为解决此问题，我们引入了一系列用于LT码的混合解码器，并提出了它们以最低解码成本恢复区块链的最优操作机制。虽然LT编码区块链架构已从存储节省和可扩展性方面得到研究，但其安全漏洞方面的认知尚不充分。针对这一研究空白，在第二部分，我们提出了针对LT编码区块链的新型拒绝服务威胁，这些威胁针对具有特定解码能力的节点，阻止其加入网络。我们提出的威胁本质上是非盲目的，即攻击者能够访问已存档的区块，并根据底层编码方案选择对其中一部分区块执行攻击。我们证明，经过优化的威胁可以达到与盲目攻击相同的破坏程度，但仅需有限的资源。总体而言，这是该领域的首项研究，为设计能够同时提供存储节省、可扩展性以及对优化威胁的抵抗力的编码区块链开辟了新的问题。