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MPC-in-the-Head (MitH) is a general framework that enables constructing efficient zero-knowledge (ZK) protocols for NP relations from secure multiparty computation (MPC) protocols. In this paper we present the first machine-checked implementations of MitH. We begin with an EasyCrypt formalization that preserves the modular structure of the original construction and can be instantiated with arbitrary MPC protocols, and secret sharing and commitment schemes satisfying standard notions of security. We then formalize various suitable components, which we use to obtain full-fledged ZK protocols for general relations. We compare two approaches for obtaining verified executable implementations. The first uses a fully automated extraction from EasyCrypt to OCaml. The second reduces the trusted computing base (TCB) and provides better performance by combining code extraction with formally verified manual low-level components implemented in the Jasmin language. We conclude with a discussion of the trade-off between the formal verification effort and the performance of resulting executables, and how our approach opens the way for fully verified implementations of state-of the-art optimized protocols based on MitH.

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This paper explores the role of formal methods as part of the user-centred design of interactive systems. An iterative process is described, developing prototypes incrementally, proving user-centred requirements while at the same time evaluating the prototypes that are executable forms of the developed models using 'traditional' techniques for user evaluation. A formal analysis complements user evaluations. This approach enriches user-centred design that typically focuses understanding on context and producing sketch designs. These sketches are often non-functional (e.g. paper) prototypes. They provide a means of exploring candidate design possibilities using techniques such as cooperative evaluation. This paper describes a further step in the process using formal analysis techniques. The use of formal methods provides a systematic approach to checking plausibility and consistency during early design stages, while at the same time enabling the generation of executable prototypes. The technique is illustrated through an example based on a pill dispenser.

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This editorial introduces the special issue of Interacting with Computer on Heterogeneous Models and Modelling Approaches for Engineering of Interactive Systems. This special issue was proposed to gather the best contributions from a series of workshops organized alongside conferences such as FM'19 (3rd World Congress on Formal Methods) and EICS'19 (11th ACM SIGCHI Symposium on Engineering Interactive Computing Systems). It also encompasses papers submitted directly to this special issue.