Inherent in the world of cryptocurrency systems and their security models is the notion that private keys-and thus assets-are controlled by individuals or individual entities. We present Liquefaction, a wallet platform that demon-strates the dangerous fragility of this foundational assumption by systemically breaking it. Liquefaction uses trusted execution environments (TEEs) to encumber private keys, i.e., attach rich, multi-user policies to their use. In this way, it enables the cryptocurrency credentials and assets of a single end-user address to be freely rented, shared, or pooled. It accomplishes these things privately, with no direct on-chain traces. Liquefaction demonstrates the sweeping consequences of TEE-based key encumbrance for the cryptocurrency land-scape. Liquefaction can undermine the security and economic models of many applications and resources, such as locked tokens, DAO voting, airdrops, loyalty points, soulbound tokens, and quadratic voting. It can do so with no on-chain and minimal off-chain visibility. Conversely, we also discuss beneficial applications of Liquefaction, such as privacy-preserving, cost-efficient DAOs and a countermeasure to dusting attacks. Importantly, we describe an existing TEE-based tool that applications can use as a countermeasure to Liquefaction. Our work prompts a wholesale rethinking of existing models and enforcement of key and asset ownership in the cryptocurrency ecosystem.

Most cryptographic protocols model a player's knowledge of secrets in a simple way. Informally, the player knows a secret in the sense that she can directly furnish it as a (private) input to a protocol, e.g., to digitally sign a message.

Secure TLS server authentication depends on reliable trust anchors. The fault intolerant design of today's system---where a single compromised trust anchor can impersonate nearly all web entities---necessitates the careful assessment of each trust anchor found in a root store. In this work, we present a first look at the root store ecosystem that underlies the accelerating deployment of TLS. Our broad collection of TLS user agents, libraries, and operating systems reveals a surprisingly condensed root store ecosystem, with nearly all user agents ultimately deriving their roots from one of three root programs: Apple, Microsoft, and NSS. This inverted pyramid structure further magnifies the importance of judicious root store management by these foundational root programs.