# Constraint-Based Monitoring of Hyperproperties

## TL;DR

This paper presents a novel runtime monitoring approach for hyperproperties using HyperLTL and Boolean constraints, enabling efficient detection of violations through satisfiability checks.

## Contribution

It introduces a constraint-based monitoring method for hyperproperties, leveraging BDDs or SAT solvers, improving over automata-based techniques.

## Key findings

- Efficient detection of hyperproperty violations at runtime.
- Comparison shows advantages over existing automata-based tools.
- Framework supports complex hyperproperties like non-interference.

## Abstract

Verifying hyperproperties at runtime is a challenging problem as hyperproperties, such as non-interference and observational determinism, relate multiple computation traces with each other. It is necessary to store previously seen traces, because every new incoming trace needs to be compatible with every run of the system observed so far. Furthermore, the new incoming trace poses requirements on future traces. In our monitoring approach, we focus on those requirements by rewriting a hyperproperty in the temporal logic HyperLTL to a Boolean constraint system. A hyperproperty is then violated by multiple runs of the system if the constraint system becomes unsatisfiable. We compare our implementation, which utilizes either BDDs or a SAT solver to store and evaluate constraints, to the automata-based monitoring tool RVHyper.