fiat-shamir transform

This work introduces revocability into the Fiat-Shamir with aborts paradigm for the first time, addressing the need for users to retract signatures under specific conditions in post-quantum signature schemes. We present a generic construction that realizes revocable signatures within a Dilithium-style framework under the no-hint, full-t parameter setting, accompanied by a rigorous security proof. Furthermore, we analyze the minor ε error introduced when extending our approach to hint-based ML-DSA variants. The proposed scheme formally supports controlled signature revocation while preserving post-quantum security, thereby filling a critical gap in existing Fiat-Shamir with aborts frameworks, which previously lacked mechanisms for revocability.

This work proposes a post-quantum secure digital signature framework based on code-based cryptography to address threats posed by quantum computing. The construction relies on two core hard problems: the restricted-error syndrome decoding problem and the linear code equivalence problem. By integrating Sigma protocols with the Fiat–Shamir transformation, the authors unify these challenges into a single, efficient, and provably secure signature scheme. Notably, this is the first approach to jointly address the restricted-error model and code equivalence within a cohesive framework. The methodology successfully instantiates both CROSS and LESS—two candidates from the second round of the NIST post-quantum standardization process—demonstrating strong competitiveness in terms of security, efficiency, and resilience against quantum attacks, thereby advancing the adoption of code-based signatures in post-quantum standardization efforts.

This work proposes a novel accountable and revocable signature scheme that simultaneously guarantees pre-claim anonymity for signers and enables secure identity revocation. Built upon the Fiat–Shamir with aborts paradigm, the construction realizes an accountable ring signature by black-boxing a one-out-of-N signature to achieve anonymity even under full key exposure, and employs binding signatures together with hidden-index commitments to confirm claims without revealing any signer-derived information. It is the first lattice-based construction to realize extended accountable signatures without requiring explicit transmission of the signer’s offset, offering unforgeability and claimability even in the presence of internal corruption. The scheme is rigorously proven secure in the (quantum) random oracle model, relying on the hardness of the decisional MLWE and MSIS problems, lattice-based one-out-of-many proofs, and hint-free full-t Dilithium-style signatures, thereby establishing a new paradigm for post-quantum privacy-enhancing signatures.

Existing TPM-based multisignature schemes require real-time interaction among participants during the commitment phase, resulting in high communication overhead, synchronization bottlenecks, and vulnerability to protocol failure upon device faults—issues particularly acute in cross-device settings. This work proposes PiTPM, the first framework for TPM-based multisignatures that eliminates inter-participant interaction by leveraging an aggregator to securely store a pre-shared random seed. Combining Schnorr multisignatures with a hybrid trust architecture, PiTPM enables deterministic generation of a global commitment without any communication among signers. The scheme produces constant-size signatures independent of the number of participants and is proven secure under EU-CMA in the random oracle model assuming the hardness of the discrete logarithm problem. Experimental evaluation demonstrates that PiTPM significantly improves both efficiency and robustness.

Formal theories of algorithms have long been confined to non-interactive settings, leaving interactive and nondeterministic algorithms without rigorous foundational treatment. Method: This work introduces a unified formal framework encompassing both non-interactive and interactive, deterministic and nondeterministic algorithms. It proposes the “prototype algorithm” as an abstract computational model and rigorously defines its behavioral semantics. Three equivalence relations—behavioral, implementation, and specification equivalence—are formally introduced; their relationships are established, and specification equivalence is proven to be the appropriate criterion for capturing essential algorithmic identity. Contribution: The framework breaks the traditional boundaries of algorithm definitions, providing the first formal foundation for interactive algorithms. It establishes a layered, extensible meta-theory of algorithms and delivers a rigorous logical basis for reasoning about algorithmic essence, correctness verification, and cross-model comparison—thereby unifying previously fragmented formal approaches under a coherent theoretical umbrella.

This work presents the first three-round authenticated key exchange (AKE) protocol secure in the commitment model without relying on long-term secret key material. Building upon the MT authenticator framework, the authors design dedicated protocols tailored to key agreement (KA) and key encapsulation mechanism (KEM) primitives, respectively, and establish session key security via a game-based proof in the unauthenticated setting. Compared to existing four-round constructions, this approach reduces communication overhead by one round while achieving comparable security guarantees under standard models. The protocol also supports unilateral authentication, thereby offering enhanced efficiency and practicality without compromising security strength.

This work addresses the high barrier to entry in formal verification of cryptographic protocols and the difficulty of tracing verification results back to concrete implementations. The authors propose a domain-specific language (DSL)-centric development methodology that pioneers a “language-first” modeling paradigm. Their approach automatically translates protocol implementations into Tamarin-verifiable models and integrates symbolic execution to ensure memory safety. This framework guarantees that general trace properties established through formal verification are correctly mapped back to the original source code. Empirical evaluation demonstrates the successful generation of precise models for Signed Diffie-Hellman and WireGuard protocols; notably, the resulting WireGuard implementation achieves interoperability, practical usability, and compositional security guarantees.

This work addresses the challenge of simultaneously achieving information-theoretic security, quantum resistance, transferability, and unforgeability against non-designated verifiers in designated verifier signature schemes. To this end, we propose a novel construction based on minimal algebraic structures over finite fields, integrating true randomness and perfect 2-out-of-2 Shamir secret sharing to support both two-party and three-party settings. Our scheme is the first to realize transferable designated verifier signatures under information-theoretic security in the quantum random oracle model, enabling public verification of receipts without revealing the validity of the underlying signature. Furthermore, it extends the framework of Fitzi et al. to accommodate quantum adversaries handling classical inputs and outputs. Compared to established post-quantum standards such as Dilithium, Falcon, and SPHINCS+, our approach offers significantly smaller key and signature sizes, providing both high efficiency and strong security for applications like blockchain systems.