Abstract Smart home platforms predominantly adopt the broker-mediated publish/subscribe model (e.g., MQTT) for seamless device-app coordination. However, this architecture introduces a fundamental privacy-functionality conflict: the broker requires plaintext metadata (topic strings) for message routing, which inadvertently exposes fine-grained user behavioral patterns to semi-trusted service providers. Furthermore, existing systems lack rigorous cryptographic enforcement for app permissions, leaving the ecosystem vulnerable to over-privileged or malicious apps. While conventional Attribute-Based Encryption (ABE) provides fine-grained read-side access control, it cannot enforce writer-bound policies and remains computationally prohibitive for resource-constrained IoT nodes. In this paper, we propose SHERLOC, a practical and privacy-preserving framework that reconciles secure message routing with fine-grained privilege control. SHERLOC introduces two core primitives: (1) Secret Queue Telemetry Transport (SQTT), which leverages a novel trapdoor-based matching mechanism to support multi-level wildcard routing while ensuring topic indistinguishability and resistance against inside keyword-guessing attacks (IKGA); and (2) Outsourced Inner-Product Access Control Encryption (OS-IPACE), an attribute-hiding scheme that enforces dual no-read and no-write security for apps by offloading intensive pairing operations to a local hub without compromising data secrecy. We provide formal security proofs reducing SHERLOC’s privacy guarantees to the SXDH assumption. Experimental results from a full-scale prototype, comprising ESP32-based devices and Android apps, demonstrate that SHERLOC incurs millisecond-level latency and maintains compatibility with legacy MQTT brokers without altering protocol semantics, making it a robust and deployable solution for modern smart home environments.

Abstract The breaches of the blockchain wallet keys greatly harm the security of blockchain transactions. To protect the secret keys, the known solutions, such as hierarchical deterministic wallets proposed in BIP32 or stealth addresses adopted in Monero, have been extensively researched. However, most of the existing works assume the key is safe, in the sense that it cannot be stolen or damaged, which is not true in practice. Moreover, current key revocation mechanisms either rely on centralized authorities, compromising decentralization, or require economic incentives to ensure nodes remain consistantly online. In this paper, we introduce Cocoon, the first blockchain wallet scheme that supports stealth addresses and provides a wallet revocation mechanism without the need for certificates. Cocoon not only ensures the privacy of wallet secret keys but also can individually revoke compromised keys with high performance. Our contributions are three-fold: First, we present the formal model and the related security definitions. Next, we give a generic construction based on the hierarchical identity-based signature, identity-based key encapsulation mechanism and non-interactive zero-knowledge proof. We then extend the scheme to the hierarchical setting for diverse scenarios. Finally, we give the implementation, and the results show that the scheme is practical.

Abstract Threshold signatures are essential for fault-tolerant applications among groups of users, such as in blockchain transactions. SM2 is a digital signature standard in China and ISO, yet its threshold variant is less developed compared to international alternatives such as ECDSA. Specifically, modern threshold signatures offer identifiable abort (ID-abort) and non-interactive online signing, but these features make threshold-SM2 costly, limiting its real-world application. In this paper, we introduce a fast threshold-SM2 with ID-abort and non-interactive online signing. We design a technology for ID-abort by checking hard-to-verify pseudononces based on their mappings in a group. By putting the message-independent computations to a presigning phase, we achieve a non-interactive online signing. We prove that our threshold-SM2 is secure in the dishonest majority model and implement it using Golang. Theoretical analysis and experimental results demonstrate that our threshold-SM2 provides rich functionalities with good performance, significantly reducing computational and communication costs compared to the state-of-the-art threshold-SM2 by Liang and Chen (FCS’ 24).

Abstract The non-transferability of a designated confirmer signature scheme allows a signer to control the verification ability of a signature, hence protecting the signer’s privacy. However, a designated confirmer signature is insufficient when the secret keys are damaged and incapable of collaborative signature generation. In this paper, we circumvent these limitations by introducing the notion of designated confirmer threshold signature. First, we present a formal security model, then give a generic construction, which utilizes threshold signature schemes, encryption schemes and $$\Sigma$$ Σ -protocols. Instantiating this generic construction, we have two specific schemes, based on threshold Schnorr and threshold ECDSA, respectively. We further design two efficient $$\Sigma$$ Σ -protocols for efficient proofs. We also implement these schemes, and the experiment results show that our schemes are practical with rich functionalities. Finally, we demonstrate interesting applications for blockchains, such as verifiable asset auctions in blockchain and traditional electronic bidding.

Abstract A ring signature is a variant of normal digital signature and protects the privacy of a specific signer in the sense that a ring signature can be verified, but the signer’s identity can only be traced to a limited set. The concept was further enhanced to threshold setting to distribute signing ability among several signers. Since threshold ring signature was introduced, it was a hard problem whether one can have efficient constructions for it. In this paper, we introduce a new generic construction of threshold ring signature, named GTRS, based on canonical identification of a specific form. Our signature consists of a polynomial (represented by $$n - t + 1$$ n - t + 1 coefficients) and a single response, resulting in significantly shorter threshold ring signatures. Instantiating the generic construction with specific DL-based components, e.g. Schnorr identification and a novel vector argument of knowledge developed in this paper, we obtain GTRS-EC, which is shorter than all existing threshold ring signatures without any trusted setup.

Abstract Atomic Cross-Chain Swap (ACCS) is one important topic in cryptocurrency, where users can securely and trustlessly exchange assets between two different blockchains. However, most known ACCS schemes assume specific scripting functionalities of the underlying blockchains, such as Hash Time Locked Contracts (HTLC). In addition, these schemes are typically only applicable to certain digital signature schemes, like Schnorr or Elliptic Curve Digital Signature Algorithm (ECDSA) signatures. In this paper, we propose a generic ACCS scheme, independent from the underlying blockchains. To the best of our knowledge, this is the first solution of this kind. Our results are as follows. First, we define a formal system model of ACCS. Next, we present a generic ACCS scheme meets our model. This scheme admits atomicity in cross-chain swaps without the need for a Trusted Third Party (TTP) and protects users’ privacy. Finally, by using the Non-Interactive Zero-Knowledge (NIZK) proof protocol as a tool, we instantiate our generic scheme for Elliptic Curve Discrete Logarithm Problem-based (ECDLP-based) signatures. In addition, we implement our scheme, and the experimental results show that our protocol outperforms the existing ACCS schemes, such as the HTLC-based schemes.

Abstract Gaussian sampling over the integers is one of the fundamental building blocks of lattice-based cryptography. Among the extensively used trapdoor sampling algorithms, it is ineluctable until now. Under the influence of numerous side-channel attacks, it is still challenging to construct a Gaussian sampler that is generic, efficient, and resistant to timing attacks. In this paper, our contribution is three-fold. First, we propose a secure, efficient exponential Bernoulli sampling algorithm. It can be applied to Gaussian samplers based on rejection samplings. We apply it to FALCON, a candidate of round 3 of the NIST post-quantum cryptography standardization project, and reduce its signature generation time by 13–14%. Second, we develop an isochronous Gaussian sampler based on rejection sampling. Our Algorithm can securely sample from Gaussian distributions with different standard deviations and arbitrary centers. We apply it to PALISADE (S&P 2018), an open-source lattice-based cryptography library. During the online phase of trapdoor sampling, the running time of the G-lattice sampling algorithm is reduced by 44.12% while resisting timing attacks. Third, we improve the efficiency of the COSAC sampler (PQC 2020). The new COSAC sampler is 1.46x–1.63x faster than the original and has the lowest expected number of trials among all Gaussian samplers based on rejection samplings. But it needs a more efficient algorithm sampling from the normal distribution to improve its performance.