Echoes of the Past: Recovering Blockchain Metrics From Merged Mining

So far, the topic of merged mining has mainly been considered in a security context, covering issues such as mining power centralization or crosschain attack scenarios. In this work we show that key information for determining blockchain metrics such as the fork rate can be recovered through data extracted from merge mined cryptocurrencies. Specifically, we reconstruct a long-ranging view of forks and stale blocks in Bitcoin from its merge mined child chains, and compare our results to previous findings that were derived from live measurements. Thereby, we show that live monitoring alone is not sufficient to capture a large majority of these events, as we are able to identify a non-negligible portion of stale blocks that were previously unaccounted for. Their authenticity is ensured by cryptographic evidence regarding both, their position in the respective blockchain, as well as the Proof-of-Work difficulty. Furthermore, by applying this new technique to Litecoin and its child cryptocur rencies, we are able to provide the first extensive view and lower bound on the stale block and fork rate in the Litecoin network. Finally, we outline that a recovery of other important metrics and blockchain characteristics through merged mining may also be possible

Bringing Order to Chaos: The Case of Collision-Resistant Chameleon-Hashes

Chameleon-hash functions, introduced by Krawczyk and Rabin at NDSS 2000, are trapdoor collision-resistant hash-functions parametrized by a public key. If the corresponding secret key is known, arbitrary collisions for the hash function can be efficiently found. Chameleon-hash functions have prominent applications in the design of cryptographic primitives, such as lifting non-adaptively secure signatures to adaptively secure ones. Recently, this primitive also received a lot of attention as a building block in more complex cryptographic applications ranging from editable blockchains to advanced signature and encryption schemes. We observe that in latter applications various different notions of collision-resistance are used, and it is not always clear if the respective notion does really cover what seems intuitively required by the application. Therefore, we revisit existing collision-resistance notions in the literature, study their relations, and - using the example of the recent redactable blockchain proposals - discuss which practical impact different notions of collision-resistance might have. Moreover, we provide a stronger, and arguably more desirable, notion of collision-resistance than what is known from the literature. Finally, we present a surprisingly simple and efficient black-box construction of chameleon-hash functions achieving this strong notion

Why blockchains need the law: Secondary rules as the missing piece of blockchain governance

Governance issues limit blockchains’ ability to evolve and face unforeseen challenges. It seems possible to argue that this impasse is because most blockchains lack meta-rules. This work considers blockchains as a socio-technical system of rules, in order to draw a comparison with legal systems. Following the comparison, one finds that most blockchains lack what, in legal theory, are considered secondary rules. That is, the meta-rule of the system. This works examines the relevant concepts and provides their definitions, then proceeds to outline concrete example of the failure of governance among popular blockchains before drawing the parallelism with legal systems and argue that secondary rules might solve some of the issues of the governance of blockchains. Secondary rules are the necessary infrastructure for building sound governance structures and a necessary condition for blockchains to succeed as a new mode of governance. The conclusion provides future research directions