UTXO$$_{\textsf {}}$$: UTXO with Multi-asset Support

A prominent use case of Ethereum smart contracts is the creation of a wide range of user-defined tokens or assets by way of smart contracts. User-defined assets are non-native on Ethereum; i.e., they are not directly supported by the ledger, but require repetitive custom code. This makes them unnecessarily inefficient, expensive, and complex. It also makes them insecure as numerous incidents on Ethereum have demonstrated. Even without stateful smart contracts, the lack of perfect fungibility of Bitcoin assets allows for implementing user-defined tokens as layer-two solutions, which also adds an additional layer of complexity.