Distributed ledger technology (DLT)—and, specifically, blockchains—are used in a variety of contexts, such as digital currency, decentralized finance, and even electronic voting. While there are many different types of DLT, each built with fundamentally different design decisions, the overarching value proposition of DLT and blockchains is that they can operate securely without any centralized control. The cryptographic primitives that enable blockchains are, by this point, quite robust, and it is often taken for granted that these primitives enable blockchains to be immutable (not susceptible to change). This report gives examples of how that immutability can be broken not by exploiting cryptographic vulnerabilities but instead by subverting the properties of a blockchain’s … Continue reading DARPA