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Differential cryptanalysis of An optimized novel lightweight block cipher for image encryption
Get PDFThis paper presents a security analysis of the ARX-based lightweight block cipher proposed by Mohanapriya and Nithish (Sci Rep 15, 36060 (2025)) for image encryption in IoT environments. The cipher employs a 64-bit key and a 64-bit block size, relying on Addition, Rotation, and XOR (ARX) operations. Our analysis demonstrates that the full-round version of this cipher is vulnerable to differential cryptanalysis. In fact, the cipher can be distinguished from a random permutation using chosen plaintexts. Consequently, the designers\u27 security claims are not fully supported
Nostalgia Cipher: Can Filtered LFSRs Be Secure Again? An Application to Hybrid Homomorphic Encryption with Sub-50 ms Latency
Get PDFLinear Feedback Shift Registers (LFSRs) combined with non linear filtering functions have long been a fundamental design for stream ciphers, offering a well-understood structure that remains easy to analyze. However, the introduction of algebraic attacks in 2003 shifted the focus toward more complex designs, as filtered LFSRs required larger registers to maintain security. While this was seen as a drawback at the time, it is no longer a limiting factor, and emerging cryptographic applications benefit from specialized designs—challenges that filtered LFSRs can effectively address.
In this work, we propose a new filtered LFSR design, called Nostalgia, tailored for Hybrid Homomorphic Encryption (HHE). We use a weightwise quadratic function as filtering function, leveraging its efficiency in the HHE setting while ensuring security against classical attacks. We also discuss the parameter selection of our design and demonstrate its efficiency in this setting by providing a proof-of-concept implementation. In terms of latency, our HHE solution outperforms current state-of-the-art for TFHE-based HHE (Baudrin et. al. Crypto 2025) by a factor of 6.1 times.
By revisiting filtered LFSRs in light of modern security requirements, we aim to renew interest in their potential applications and stimulate further cryptanalysis efforts
DPaaS: Improving Decentralization by Removing Relays in Ethereum PBS
Get PDFProposer-Builder Separation (PBS) in Ethereum improves decentralization and scalability by offloading block construction to specialized builders. In practice, MEV-Boost implements PBS via a side-car protocol with trusted relays between proposers and builders, resulting in increased centralization as well as security (e.g., block stealing) and performance concerns. We propose Decentralized Proposer-as-a-Service (DPaaS), a deployable architecture that eliminates centralized relays while preserving backward compatibility with Ethereum’s existing consensus layer. Our insight is that we can reduce centralized trust by distributing the combined roles of the proposer and relay to a set of Proposer Entities (PEs), each running in independent Trusted Execution Environments (TEEs). For compatibility, DPaaS presents itself to Ethereum as a single validator, leveraging threshold and aggregation properties of the BLS signature scheme used in Ethereum. At the same time, DPaaS protocols ensure fair exchange between builders and proposers even in the face of a small fraction of TEE failures or partial synchrony in networks. Our evaluation, deployed across four independent cloud hosts and driven by real-world traces, shows that DPaaS achieves less than 5 ms bid processing latency and 55.75 ms latency from the end of auction to block proposal -- demonstrating that DPaaS can offer security and decentralization benefits while providing strong performance
A note on mutual correlated agreement for Reed-Solomon codes
Get PDFWe outline how to generalize the Guruswami-Sudan list decoder anal-
ysis from Ben–Sasson, Carmon, Ishai, Kopparty and Saraf [BCI+20] in
order to obtain a “global” proximity gap, called mutual correlated agree-
ment in Arnon, Chiesa, Fenzi and Yogev [WHIR 2024], or strong correlated agreement in Zeilberger [Khatam 24]
SoK: Blockchain Oracles Between Theory and Practice
Get PDFSmart contract-based decentralized applications (dApps) have become an ever-growing way to facilitate complex on-chain operations. Oracle services strengthened this trend by enabling dApps to access real-world data and respond to events happening outside the blockchain ecosystem. A large number of academic and industrial oracle solutions have emerged, capturing various designs, capabilities, and security assumptions/guarantees. This rapid development makes it challenging to comprehend the landscape of oracles, understand their trade-offs, and build on them.
To address these challenges, we develop a systematization of knowledge for blockchain oracle services. To the best of our knowledge, our work is the first to provide extensive study of oracles while empirically investigating their capabilities in practice. After examining the general design framework of oracles, we develop a multi-dimensional systematization framework assessing existing solutions based on their capabilities, trust and security assumption/guarantees, and their underlying design architecture. To further aid in this assessment, we conduct a number of empirical experiments to examine oracle deployed in practice, thus offering additional insights about their deployment maturity, usage popularity, performance, and ease-of-use. We go on to distill a number of insights and gaps, thus providing a guide for practitioners (on the use of these oracles) and researchers (by highlighting gaps and open problems)
A Comprehensive Analysis of the AKMA+ Protocol
Get PDFWith the rapid advancement of 5G networks and the increasing demand for secure application access, the Authentication and Key Management for Applications (AKMA) framework was developed by the 3rd Generation Partnership Project (3GPP) to provide unified authentication and key management for diverse 5G services. In response to the security and privacy concerns identified in the current AKMA protocol, as outlined in 3GPP TR 33.835, Yang et al. proposed an enhanced, standard-compatible 5G AKMA protocol known as AKMA+[14].
This paper presents a comprehensive analysis of AKMA+, discovering two critical vulnerabilities: (1) the compromise of the AKMA Anchor Function (AAnF), which enables adversaries to impersonate legitimate users; and (2) the persistent storage of multiple anchor keys, which heightens the risk of key exposure. These vulnerabilities arise from the reliance on the authentication framework inherent in existing AKMA+ models. This architectural dependency introduces fundamental security risks that cannot be adequately mitigated through incremental modifications to the current design.
Furthermore, we observe that AKMA+ faces challenges in aligning with the standard account-based authentication model, which is incompatible with existing user practices within information systems. Additionally, we find that providing account-based authentication functionality without compromising privacy poses significant difficulties
Security of Private Set Operation Schemes: Separations and Implications
Get PDFThe private set operation (PSO) scheme [Rafiee-Khazaei, Comput. J. 2020] is a cryptographic primitive that enables a user to securely outsource their dataset to cloud server, and then when needed, securely issue common set operation queries to the server and receive the results. This primitive has always been of interest to researchers because it supports set operations, which are the most basic mathematical operations and are used in a wide range of real-world applications. In previous research, security notions such as: naSIM and aIND have been introduced for it. In this paper, we develop the standard security notions for PSO schemes: an adaptive version of simulation-based security notion (aSIM) and a non-adaptive version of indistinguishability-based security notion (naIND). We also study the relation between these security notions and determine their implications and separations. In addition to these, we also provide a summary of the available PSO constructions and their security level, and introduce research potentials in this regard
Key-Recovery Side-Channel Attack on the Berlekamp-Massey Decoding Algorithm in the Classic McEliece KEM
Get PDFIn this article, we provide the first side-channel attack on the Berlekamp-
Massey (BM) algorithm, which is the decoder used in the decryption process of
the Classic McEliece KEM. We conduct a chosen plaintext key recovery attack
that exploits the power consumption of the BM, which is highly dependent on the
secret Goppa support elements. We exploit the relation between plaintexts of small
Hamming weight, secret elements in the Goppa support and power traces using an
efficient Template Attack. Our method completely recovers the secret Goppa support
for the first parameter set of the Classic McEliece KEM using a single attack trace
per secret coefficient. The entire support can be recovered in less than 7 seconds on
a standard computer. Our experiments are performed using the ChipWhisperer-Lite
board platform with the ARM Cortex-M4 microcontroller
Anonymous Authentication and Key Agreement, Revisited
Get PDFIn NDSS 2024, Yu~et al. proposed AAKA, an Anonymous Authentication and Key Agreement scheme designed to protect users\u27 privacy from mobile tracking by Mobile Network Operators (MNOs). AAKA aims to provide both anti-tracking privacy and traceability (lawful de-anonymization), allowing subscribers to access the network via anonymous proofs while enabling a Law Enforcement Agency (LEA) to trace the real identity if misbehaviors are detected. However, we identify that the AAKA scheme in NDSS 2024 is insecure since the subscriber\u27s identity is exposed within the protocol, thereby failing to achieve the claimed privacy and traceability.
Building on the repair of AAKA, we propose AAKA+, Anonymous Authentication and Key Agreement with Verifier-Local Revocation, a new mobile authentication scheme, to ensure privacy against mobile tracking. In addition to the privacy and traceability introduced in NDSS 2024, AAKA+ additionally allows the MNO to immediately assert whether the associated subscriber has been traced and revoked upon receiving an anonymous proof. We formally define the syntax and the security model of AAKA+ and propose two concrete schemes, AAKA+BB and AAKA+PS, based on the Boneh-Boyen signature and the Pointcheval-Sanders signature schemes, respectively. Both AAKA+BB and AAKA+PS are pairing-free on the user equipment side and compatible with existing cellular infrastructure. Experimental results show that our schemes are practical, with anonymous proof generation taking approximately 18 milliseconds for a constrained device
Taming Iterative Grinding Attacks on Blockchain Beacons
Get PDFRandom beacons play a critical role in blockchain protocols by providing publicly verifiable, unpredictable randomness essential for secure assignment of protocol roles such as block producers and committee membership. In the interest of efficiency, many deployed blockchains adopt beacon algorithms that suffer from grinding: an adversarial attack in which a party exploits freedom given by the protocol to bias the outcome of the random beacon by resampling it several times and picking the most desirable outcome. To compound the problem, beacons often operate in an iterative manner, where the beacon output produced during one protocol epoch serves as the random seed for the beacon’s invocation in the next epoch. This amplifies the security threat, as such attacks may then aggregate their power over many epochs.
In this article, we formulate a generic framework for information-theoretic analysis of grinding in iterated randomness beacons. We define the natural grinding capacity of a beacon, intuitively corresponding to the amount of grinding it allows with a uniformly random seed. We then prove that sufficiently strong tail bounds on this quantity can be transformed into a guarantee on smooth min-entropy of the iterated beacon’s output, even conditioned on all past outputs and irrespective of the inner workings of the beacon. Such min-entropy guarantees can immediately be translated into corresponding statements about various applications of the beacon to committee selection, incentives, or underlying protocol security.
Our main technical result concerns conventional longest-chain protocols, where we establish that the combinatorial structure of the forest of longest chains can be leveraged to control grinding. Instantiating the generic framework with these grinding upper bounds, we establish that the randomness beacon of the Ouroboros Praos protocol is secure against adversaries controlling up to about 12% of stake—even
without any assumptions bounding the adversarial computational power invested into grinding. This is a qualitatively new guarantee for the protocol