  Extractable Value refers to a wide class of economic attacks to public
blockchains, where adversaries with the power to reorder, drop or insert
transactions in a block can "extract" value from smart contracts. Empirical
research has shown that mainstream protocols, like e.g. decentralized
exchanges, are massively targeted by these attacks, with detrimental effects on
their users and on the blockchain network. Despite the growing impact of these
attacks in the real world, theoretical foundations are still missing. We
propose a formal theory of Extractable Value, based on a general, abstract
model of blockchains and smart contracts. Our theory is the basis for proofs of
security against Extractable Value attacks.
