"From Static to Protected and Mutable Non-Fungible Tokens: Design and Evaluation Across Usage Scenarios"

The increasing adoption of decentralised technologies, such as blockchain, is reshaping the way distributed systems are used and, in particular, how digital and physical resources are represented and managed. While tokenisation techniques have enabled the representation of unique and verifiable artefacts on the blockchain, Non-Fungible Tokens (NFTs), the most popular standards used to encode them still provide limited support for those resources that need to change over time. Updates to their content are handled through poorly structured, weakly regulated, and often opaque mechanisms, making it difficult to model assets whose lifecycle requires controlled modifications, and verifiable state transitions. This thesis addresses these limitations and introduces a conceptual and operational framework for the structured, controlled, and traceable man- agement of asset mutability within blockchain-based ecosystems running on Ethereum-compatible platforms. The proposed approach formalises the mu- tability of asset attributes, defines an explicit model for updates, and inte- grates on-chain authorisation mechanisms to ensure that every modification, every transfer and every minting operation is performed in accordance with predefined policies and in a permanently verifiable manner. The thesis defines update-control rules, more fine-grained metadata rep- resentations, and coordination schemes that enable creators, owners, and authorised actors to collaborate safely on the modification of a resource. The validity of the framework is assessed through the application of real use cases and simulation tools that analyse performance, costs, and behavioural properties, as well as the long-term sustainability in the blockchain across different scenarios. The results show that a more precise and structured treatment of muta- bility significantly enhances the expressiveness, reliability, applicability, and, iii most importantly, the intrinsic value of blockchain-based asset representa- tions. This provides a more realistic and flexible management of the lifecycle of digital resources, while opening new directions towards future develop- ments in areas such as decentralised identity, cross-chain interoperability, and distributed collaborative systems.