arXiv subjects

Matteo Teodori

Publications and source records attributed to Matteo Teodori.

4 recordsLinked to original sources

arXiv2026

NEBULA: A Language - Independent Specification for Opaque Rotating Refresh Tokens

Refresh tokens are among the most sensitive credentials in modern authentication systems: long-lived, bearer-style, and sufficient to mint access tokens for days or weeks. RFC 9700, the current Best Current Practice for OAuth 2.0 security, mandates that refresh tokens issued to public clients be rotated on every use with replay (reuse) detection, or be sender-constrained. But the BCP specifies policy, not mechanism: it prescribes no wire format, no storage schema, no ordering of verification steps, no concurrency contract, and no semantics for edge cases such as lost-response retries or key rotation. Implementations may therefore diverge in precisely the corner cases that determine security outcomes. We present NEBULA, a precise, language-independent specification of the RFC 9700 refresh-token model, together with ten conformant reference implementations (TypeScript, Python, Go, Rust, Java, PHP, C#, Ruby, Elixir, Dart). NEBULA tokens are opaque -- a 128-bit public selector and a 256-bit secret verifier, both CSPRNG output, carrying no claims and no signature -- so token validity is a property of server-side state rather than of cryptographic verification. Its conformance methodology publishes the behavioural suite as data rather than as prose: 38 scenarios in one machine-readable file that every implementation executes through a thin per-language runner, so that drift by transcription is structurally excluded. We describe the specification -- including a compare-and-set rotation contract that closes a reproducible bypass of reuse detection under concurrent refresh -- analyse its security properties including its post-quantum posture, and report on cross-language conformance as a method for multi-implementation security specifications. The specification, implementations, and conformance artefacts are open source under the Apache License 2.0.

cs.CR↗

arXiv2025

Gas mixing through a Smoothed Particle Hydrodynamics approach

Transport and mixing of gas species are of particular interest in planetary environments, where interactions among multiple species can occur within confined or porous media. In this work, we present a novel Smoothed Particle Hydrodynamics (SPH) approach for modeling the mixing of binary gas species. The model treats each gas as a separate fluid governed by its own set of Euler equations, coupled through collisional momentum and energy exchange terms derived from a kinetic relaxation model based on the Boltzmann equation. The numerical scheme employs a first-order operator splitting approach combined with a two-step Euler integrator. In this setup, the hydrodynamic evolution is first computed using standard SPH techniques to handle pressure forces. This is followed by a separate correction step that accounts for interspecies collisional exchanges. Such a decoupled treatment enables the use of a larger timestep dictated by hydrodynamics rather than the typically much smaller collisional timescale, enhancing computational efficiency. The model achieves good accuracy in reproducing the equilibration of density and temperature in a range of molecular mass ratios. Its modular structure supports natural extensions to polyatomic mixtures and enables the inclusion of additional physics, such as gas-solid interactions with dust and ice. These features make the method particularly well-suited for applications involving confined, multi-component gas systems, such as those expected during the ESA ExoMars mission.

astro-ph.EP↗

arXiv2025

Nanodroplet Condensation on Solid Surfaces

This paper deals with the condensation of liquid droplets on hydrophobic and hydrophilic surfaces. A stochastic mesoscale model based on the theory of fluctuating hydrodynamics and the thermodynamics of a diffuse interface approach shows how direct simulation of the vapour-liquid transition from the nucleation process to droplet hydrodynamics can be achieved. Such simulations explain the role of wettability in filmwise and dropwise condensation regimes and the main limitations of classical nucleation theory.

cond-mat.soft↗

arXiv2022

Generalization of the Fokker-Planck equation for stellar orbit diffusion in multi-mass star systems

We improve the standard theory of collisional stellar systems by considering the presence of a continuous mass distribution. The calculus of the diffusion coefficients is generalized and a new expression of the Fokker-Planck equation is found for multi-mass systems. A King-like distribution function, which validates the basic assumptions of most multi-mass models for Globular Clusters existing in literature, is obtained.

astro-ph.GA↗