arXiv subjects

Yukihiro Oda

Publications and source records attributed to Yukihiro Oda.

6 recordsLinked to original sources

arXiv2026

Type-based information flow analysis for $\pi$-calculus with a dynamically extensible security lattice

We develop a type system for secure information flow where new security levels can be created and inserted into the security lattice dynamically, i.e., even in the middle of an execution of a system. Our system is formalized by extending Kobayashi's type-based secure information flow analysis for Milner's pi-calculus, which is one of the most expressive models (or "languages") supporting both sequential and concurrent computations, with concise syntax, reduction-based semantics, and bisimulation equivalence as a robust formalization of secrecy as non-interference. The development required careful treatment of extensions of lattices themselves as well as deliberate generalization from the simple 2-element lattice (consisting of only High and Low) in the original system.

cs.CR↗

arXiv2025

A study of cut-elimination for a non-labelled cyclic proof system for propositional dynamic logics

Dynamic logic is a modal logic for reasoning about programs. A cyclic proof system is a proof system that allows proofs containing cycles and is an alternative to a proof system containing (co-)induction. This paper introduces a sequent calculus and a non-labelled cyclic proof system for an extension of propositional dynamic logic obtained by adding backwards modal operators. We prove the soundness and completeness of these systems and show that cut-elimination fails in both. Moreover, we show the cut-elimination property of the cyclic proof system for propositional dynamic logic obtained by restricting ours.

cs.LO↗

arXiv2025

Cyclic Proofs in Hoare Logic and its Reverse

We examine the relationships between axiomatic and cyclic proof systems for the partial and total versions of Hoare logic and those of its dual, known as reverse Hoare logic (or sometimes incorrectness logic). In the axiomatic proof systems for these logics, the proof rules for looping constructs involve an explicit loop invariant, which in the case of the total versions additionally require a well-founded termination measure. In the cyclic systems, these are replaced by rules that simply unroll the loops, together with a principle allowing the formation of cycles in the proof, subject to a global soundness condition that ensures the well-foundedness of the circular reasoning. Interestingly, the cyclic soundness conditions for partial Hoare logic and its reverse are similar and essentially coinductive in character, while those for the total versions are also similar and essentially inductive. We show that these cyclic systems are sound, by direct argument, and relatively complete, by translation from axiomatic to cyclic proofs.

cs.LO↗

arXiv2025

A study for recovering the cut-elimination property in cyclic proof systems by restricting the arity of inductive predicates

The framework of cyclic proof systems provides a reasonable proof system for logics with inductive definitions. It also offers an effective automated proof search procedure for such logics without finding induction hypotheses. Recent researches have shown that the cut-elimination property, one of the most fundamental properties in proof theory, of cyclic proof systems for several logics does not hold. These results suggest that a naive proof search, which avoids the Cut rule, is not enough. This paper shows that the cut-elimination property still fails in a simple cyclic proof system even if we restrict languages to unary inductive predicates and unary functions, aiming to clarify why the cut-elimination property fails in the cyclic proof systems. The result in this paper is a sharper one than that of the first authors' previous result, which gave a counterexample using two ternary inductive predicates and a unary function symbol to show the failure of the cut-elimination property in the cyclic proof system of the first-order logic.

cs.LO↗

arXiv2025

Proof systems for partial incorrectness logic (partial reverse Hoare logic)

Partial incorrectness logic (partial reverse Hoare logic) has recently been introduced as a new Hoare-style logic that over-approximates the weakest pre-conditions of a program and a post-condition. It is expected to verify systems where the final state must guarantee its initial state, such as authentication, secure communication tools and digital signatures. However, the logic has only been given semantics. This paper defines two proof systems for partial incorrectness logic (partial reverse Hoare logic): ordinary and cyclic proof systems. They are sound and relatively complete. The relative completeness of our ordinary proof system is proved by showing that the weakest pre-condition of a while loop and a post-condition is its loop invariant. The relative completeness of our cyclic proof system is also proved by providing a way to transform any cyclic proof into an ordinary proof.

cs.LO↗

arXiv2024

The failure of cut-elimination in cyclic proof for first-order logic with inductive definitions

A cyclic proof system is a proof system whose proof figure is a tree with cycles. The cut-elimination in a proof system is fundamental. It is conjectured that the cut-elimination in the cyclic proof system for first-order logic with inductive definitions does not hold. This paper shows that the conjecture is correct by giving a sequent not provable without the cut rule but provable in the cyclic proof system.

cs.LO↗