International Association
for Cryptologic Research

The world has seen an influx of connected devices through both smart devices and smart cities, paving the path forward for the Internet of Things (IoT). These emerging intelligent infrastructures and applications based on IoT can be beneficial to users only if essential private and secure features are assured. However, with constrained devices being the norm in IoT, security and privacy are often minimized. In this paper, we first categorize various existing privacy-enhancing technologies (PETs) and assessment of their suitability for privacy-requiring services within IoT. We also categorize potential privacy risks, threats, and leakages related to various IoT use cases. Furthermore, we propose a simple novel privacy-preserving framework based on a set of suitable privacy-enhancing technologies in order to maintain security and privacy within IoT services. Our study can serve as a baseline of privacy-by-design strategies applicable to IoT based services, with a particular focus on smart things, such as safety equipment.

Single Sign-On (SSO) is becoming an increasingly popular authentication method for users that leverages a trusted Identity Provider (IdP) to bootstrap secure authentication tokens from a single user password. It alleviates some of the worst security issues of passwords, as users no longer need to memorize individual passwords for all service providers, and it removes the burden of these service to properly protect huge password databases. However, SSO also introduces a single point of failure. If compromised, the IdP can impersonate all users and learn their master passwords. To remedy this risk while preserving the advantages of SSO, Agrawal et al. (CCS'18) recently proposed a distributed realization termed PASTA (password-authenticated threshold authentication) which splits the role of the IdP across $n$ servers. While PASTA is a great step forward and guarantees security as long as not all servers are corrupted, it uses a rather inflexible corruption model: servers cannot be corrupted adaptively and --- even worse --- cannot recover from corruption. The latter is known as proactive security and allows servers to re-share their keys, thereby rendering all previously compromised information useless.

In this work, we improve upon the work of PASTA and propose a distributed SSO protocol with proactive and adaptive security (PESTO), guaranteeing security as long as not all servers are compromised at the same time. We prove our scheme secure in the UC framework which is known to provide the best security guarantees for password-based primitives. %as it avoids any unrealistic assumption on password distributions. The core of our protocol are two new primitives we introduce: partially-oblivious distributed PRFs and a class of distributed signature schemes. Both allow for non-interactive refreshs of the secret key material and tolerate adaptive corruptions. We give secure instantiations based on the gap one-more BDH and RSA assumption respectively, leading to a highly efficient 2-round PESTO protocol. We also present an implementation and benchmark of our scheme in Java, realizing OAuth-compatible bearer tokens for SSO, demonstrating the viability of our approach.

Learning with Errors (LWE) and Ring-LWE (RLWE) problems allow the construction of efficient key exchange and public-key encryption schemes. However, while improving the security through the use of error distributions with large standard deviations, the decryption failure rate increases as well. Currently, the independence of individual coefficient failures is assumed to estimate the overall decryption failure rate of many LWE/RLWE schemes. However, previous work has shown that this assumption is not correct. This assumption leads to wrong estimates of the decryption failure probability and consequently of the security level of the LWE/RLWE cryptosystem. An exploration of the influence of the LWE/RLWE parameters on the stochastic dependence among the coefficients is still missing. In this paper, we propose a method to analyze the stochastic dependence between decryption failures in LWE/RLWE cryptosystems. We present two main contributions. First, we use statistical methods to analyze the influence of fixing the norm of the error distribution on the stochastic dependence among decryption failures. The results have shown that fixing the norm of the error distribution indeed reduces the stochastic dependence of decryption failures. Therefore, the independence assumption gives a very close approximation to the true behavior of the cryptosystem. Second, we analyze and explore the influence of the LWE/RLWE parameters on the stochastic dependence. This exploration gives designers of LWE/RLWE based schemes the opportunity to compare different schemes with respect to the inaccuracy made by using the independence assumption. This work shows that the stochastic dependence depends on three LWE/RLWE parameters in different ways: i) it increases with higher lattice dimensions ($n$) and higher standard deviations of the error distribution ($\sqrt{k/2}$); and ii) it decreases with higher modulus ($q$).

A trapdoor over NTRU lattice proposed by Ducas, Lyubashevsky and Prest~(ASIACRYPT 2014) has been widely used in various crytographic primitives such as identity-based encryption~(IBE) and digital signature, due to its high efficiency compared to previous lattice trapdoors. However, the most of applications use this trapdoor with the power-of-two cyclotomic rings, and hence to obtain higher security level one should double the ring dimension which results in a huge loss of efficiency.

In this paper, we give a new way to overcome this problem by introducing a generalized notion of NTRU lattices which we call \emph{Module-NTRU}~(MNTRU) lattices, and show how to efficiently generate a trapdoor over MNTRU lattices. Moreover, beyond giving parameter flexibility, we further show that the Gram-Schmidt norm of the trapdoor can be reached to about $q^{1/d},$ where MNTRU covers $d \ge 2$ cases while including NTRU as $d = 2$ case. Since the efficiency of trapdoor-based IBE is closely related to the Gram-Schmidt norm of trapdoor, our trapdoor over MNTRU lattice brings more efficient IBE scheme than the previously best one of Ducas, Lyubashevsky and Prest, while providing the same security level.

Distributed computational networks allow for effective hardware encryption systems and the rise of Quantum level encryption as well for Qubit based processing. Part of the reason distributed architecture can lead to Qubit level encryption is similar mechanisms applied to cryptographic hashing. In the work presented in this paper, we will look at the decentralized-internet SDK and protocol, grid computing architecture, and mathematical approaches to parallel Qubit-based processing. The utilization for hardware oriented cryptography, modeled around distributed computing, will allow for an even more secure approach to Quantum authentication. The importance of works such as these, are due to the lack of security classical computing has in relation to encryption. Once mathematical formalities surpass NP-hardness, classical encryption mechanisms can be easily surpassed. However, a latent model for increased complexity in post-quantum level encryption likely forbids this trade-off. Given that Quantum Algorithms speed up superpolynomially, than deterministic NP-hardness would likely pose less harm to quantum encryption networks. Furthermore, with Qubit-based parallel processing, complexity models for encryption can harden in difficulty over time.

In a highly influential paper from fifteen years ago, Canetti, Goldreich, and Halevi showed a fundamental separation between the Random Oracle Model (ROM) and the Standard Model. They constructed a signature scheme which can be shown to be secure in the ROM, but is insecure when instantiated with any hash function (and thus insecure in the standard model). In 2011, Boneh et al. defined the notion of the Quantum Random Oracle Model (QROM), where queries to the random oracle may be made in quantum superposition. Because the QROM generalizes the ROM, a proof of security in the QROM is stronger than one in the ROM. This leaves open the possibility that security in the QROM could imply security in the standard model. In this work, we show that this is not the case, and that security in the QROM cannot imply standard model security. We do this by showing that the original schemes that show a separation between the standard model and the ROM are also secure in the QROM. We consider two schemes that establish such a separation, one with length-restricted messages, and one without, and show both to be secure in the QROM. Our results give further understanding to the landscape of proofs in the ROM versus the QROM or standard model, and point towards the QROM and ROM being much closer to each other than either is to standard model security.

Event date: 1 May to 22 May 2020
Submission deadline: 22 February 2020

The Institute of Cybersecurity and Cryptology (iC2) as a part of the School of Computing and Information Technology (SCIT) is seeking a Lecturer with expertise in cyber security. The primary task of this position is to support the newly developed online course in Master of Cyber Security. Experience with delivering online course in cyber security is highly desirable.

Closing date for applications:

Contact: Professor Willy Susilo

More information: https://uowjobs.taleo.net/careersection/in/jobdetail.ftl?job=191851&tz=GMT%2B11%3A00&tzname=Australia%2FSydney

The Institute of Cybersecurity and Cryptology (iC2) as a part of The School of Computing and Information Technology (SCIT) is looking to recruit two new staff members (Level B) to start ideally to be ready to teach in Spring 2020 predominately to meet the teaching requirements by UOW's SWS undertaking. SCIT aims to be a world class Research School and this position is expected to contribute towards that aim. One important part of the degrees offered by SCIT is the Bachelor of Computer Science (majoring cybersecurity) and Master of Computer Science (with major in Information Security).

Closing date for applications:

Contact: Professor Willy Susilo

More information: https://uowjobs.taleo.net/careersection/in/jobdetail.ftl?job=191859&tz=GMT%2B11%3A00&tzname=Australia%2FSydney

The Institute of Cybersecurity and Cryptology (iC2) as a part of the School of Computing and Information Technology (SCIT) is seeking a full-time continuing Associate Professor with expertise in cyber security. The position will act as the Academic Program Director for delivering a new degree for the Master in Cyber Security.

Closing date for applications:

Contact: Willy Susilo

More information: https://uowjobs.taleo.net/careersection/in/jobdetail.ftl?job=191858&tz=GMT%2B11%3A00&tzname=Australia%2FSydney

Event date: 8 July to 10 July 2020
Submission deadline: 14 February 2020
Notification: 15 April 2020

Simplistic assumptions, modeling attack discovery by a Poisson point process, lead to quantifiable statistical estimates for security assurances, supporting the wisdom that more independent effort spent on cryptanalysis leads to better security assurance, but hinting security assurance also relies significantly upon general optimism.

The estimates also suggest somewhat better security assurance from compounding two independent cryptosystems, but perhaps not enough to outweigh the extra cost.

We investigate the minimal assumptions necessary for minimal interaction zero-knowledge type primitives—ZAPs (two-round, public coin, witness indistinguishable proofs), NIWI (non-interactive witness indistinguishable proofs) and NIZK (non-interactive zero-knowledge proofs)—in the standard (no trusted setup) model. Since our goal is to obtain constructions from Minicrypt and/or worst-case assumptions only, we consider the setting where the prover is computationally more powerful than the simulator/zero-knowledge distinguisher. This covers both the traditional setting of computationally unbounded provers, as well as a new “fine-grained” setting that we introduce, where the prover is polynomial time and the verifier/simulator/zero-knowledge adversary are in a lower complexity class, such as NC1.

We present constructions of ZAPs and NIWI for AM from Minicrypt and worst-case assumptions. We also present (a form of) NIZK with uniform soundness for NP, from Minicrypt and worst-case assumptions. We present analogous “fine-grained” constructions of all of the above, where the zero- knowledge adversary is limited to NC1. Specifically, we achieve “fine-grained” ZAPs and NIWI for NP from worst-case assumptions only and achieve a form of “fine-grained” NIZK with uniform soundness for NP from worst-case and Minicrypt assumptions.

The active participation of external entities in the manufacturing flow has produced numerous hardware security issues in which piracy and overproduction are likely to be the most ubiquitous and expensive ones. The main approach to prevent unauthorized products from functioning is logic encryption that inserts key-controlled gates to the original circuit in a way that the valid behavior of the circuit only happens when the correct key is applied. The challenge for the security designer is to ensure neither the correct key nor the original circuit can be revealed by different analyses of the encrypted circuit. However, in state-of-the-art logic encryption works, a lot of performance is sold to guarantee security against powerful logic and structural attacks. This contradicts the primary reason of logic encryption that is to protect a precious design from being pirated and overproduced. In this paper, we propose a bilateral logic encryption platform that maintains high degree of security with small circuit modification. The robustness against exact and approximate attacks is also demonstrated.

Common for the overwhelming majority of privacy-preserving greater-than integer comparison schemes is that cryptographic computations are conducted in a bitwise manner. To ensure the secrecy, each bit must be encoded in such a way that nothing is revealed to the opposite party. The most noted disadvantage is that the computational and communication cost of the bitwise encoding is as best linear to the number of bits. Also, many proposed schemes have complex designs that may be difficult to implement and are not intuitive. Carlton et al. proposed in 2018 an interesting scheme that avoids bitwise decomposition and works on whole integers. % It uses a special composite RSA modulus. A variant was proposed by Bourse et al. in 2019. In this paper, we show that in particular the Bourse scheme does not provide the claimed security. Inspired by the two mentioned papers, we propose a comparison scheme with a somewhat simpler construction and with clear security reductions.

Internet of Things(IoT) consists of a large number of interconnected coexist heterogeneous entities, including Radio-frequency identification(RFIDs) based devices and other sensors to detect and transfer various information such as temperature, personal health data, brightness, etc. Security, in particular, authentication, is one of the most important parts of information security infrastructure in  IoT systems. Given that an IoT system has many resource-constrained devices, a goal could be designing a proper authentication protocol that is lightweight and can resist against various common attacks, targeting such devices. Recently, using Physical Unclonable Functions (PUF) to design lightweight authentication protocols has received a lot of attention among researchers. In this paper, we analyze two recently proposed authentication protocols based on PUF chains called PHEMAP and Salted PHEMAP. We show that these protocols are vulnerable to impersonate, desynchronization and traceability attacks.

We review several widely deployed solutions for the Byzantine Fault Tolerance (BFT) problem and analyze their security in asynchronous networks. There are two types of widely accepted definitions for partial synchronous net- works. In the Type I network, Denial of Service (DoS) attack is not allowed and in the Type II network, DoS attack is allowed before the Global Stabilization Time (GST). When DoS attack is allowed, the point-to-point communication channel and the broadcast channel are not reliable. We show that if either the broadcast channel or the point-to-point communication channel is not reliable (before or after GST) then several widely deployed BFT protocols such as PBFT and Tendermint BFT would reach a deadlock and could not achieve liveness property. Specifically, we show that if a malicious participant could broadcast a message to a subset of users instead of all users (before or after GST), then PBFT, Tendermint BFT, and several other BFT systems (e.g., Polkadot’s GRANDPA) would reach a deadlock. To make things worse, we show that, for most of our attacks, the adversary only needs to control one participant to carry out the attack instead of controlling (n-1)/3 participants. Thus these BFT protocols are not secure in the Type II partial synchronous networks. Furthermore, in these protocols, if a participant does not receive appropriate messages within a fixed time period, it initiates a view change process. After a view change, participants will no long accept messages from previous views. Thus our attacks on these protocols in Type II networks will work in the Type I network also. Consequently, these protocols are not secure in any of the widely accepted partial synchronous networks. It should be noted that PBFT has been adopted in many blockchain systems such as Hyperledger sawtooth and Tendermint BFT has been adopted in more than 40% deployed Proof of Stake Blockchains such as Cosmos and Hyperledger burrow. Based on our analysis of BFT security requirements for partial synchronous networks, we propose a BFT protocol BDLS and prove its security in partial synchronous networks. The BDLS protocol could be used in several application scenarios such as state machine replication or as blockchain finality gadgets.

This paper presents an attack based on side-channel information and information set decoding on the Niederreiter cryptosystem and an evaluation of the practicality of the attack using a physical side channel. First, we describe a basic plaintext-recovery attack on the decryption algorithm of the Niederreiter cryptosystem. Our attack is an adaptation of the timing side-channel plaintext-recovery attack by Shoufan et al. from 2010 on the McEliece cryptosystem using the non-constant time Patterson's algorithm for decoding. We then enhance our attack by utilizing an Information Set Decoding approach to support the basic attack and we introduce column chunking to further significantly reduce the number of required side-channel measurements. Our practical evaluation of the attack targets the FPGA-implementation of the Niederreiter cryptosystem in the NIST submission ``Classic McEliece'' with a constant time decoding algorithm and is feasible for all proposed parameters sets of this submission. The attack idea is to distinguish between successful and failed error correction based on the Hamming weight of the decrypted plaintext using the electromagnetic field as side channel. We theoretically estimate that our attack improvements have a significant impact on reducing the number of required side-channel traces. We confirm our findings experimentally and run successful attacks against the ``Classic McEliece'' NIST submission parameter sets. E.g., for the 256bit-security parameter set kem/mceliece6960119 we require starting from a basic attack with 6962 traces over a plain ISD approach with 5415 traces down to on average about 606 traces to mount a successful plaintext recovery attack.

Given the inherent ad-hoc nature of popular communication platforms, out-of-band authenticated key-exchange protocols are becoming widely deployed: Key exchange protocols that enable users to detect man-in-the-middle attacks by manually authenticating one short value. In this work we put forward the notion of immediate key delivery for such protocols, requiring that even if some users participate in the protocol but do not complete it (e.g., due to losing data connectivity or to other common synchronicity issues), then the remaining users should still agree on a shared secret. A property of a similar flavor was introduced by Alwen, Correti and Dodis (EUROCRYPT '19) asking for immediate decryption of messages in user-to-user messaging while assuming that a shared secret has already been established -- but the underlying issue is crucial already during the initial key exchange and goes far beyond the context of messaging.

Equipped with our immediate key delivery property, we formalize strong notions of security for out-of-band authenticated group key exchange, and demonstrate that the existing protocols either do not satisfy our notions of security or are impractical (these include, in particular, the protocols deployed by Telegram, Signal and WhatsApp). Then, based on the existence of any passively-secure key-exchange protocol (e.g., the Diffie-Hellman protocol), we construct an out-of-band authenticated group key-exchange protocol satisfying our notions of security. Our protocol is inspired by techniques that have been developed in the context of fair string sampling in order to minimize the effect of adversarial aborts, and offers the optimal tradeoff between the length of its out-of-band value and its security.

Updatable encryption allows a client to outsource ciphertexts to some untrusted server and periodically rotate the encryption key. The server can update ciphertexts from an old key to a new key with the help of an update token, received from the client, which should not reveal anything about keys or plaintexts to an adversary. We provide a new and highly efficient updatable encryption scheme called SHINE. Ciphertext generation consists of applying one permutation and one exponentiation (per message block), while updating ciphertexts requires just one exponentiation. We also define a new security notion for updatable encryption schemes that implies prior notions (for schemes with randomized and deterministic updates). We prove that SHINE and the previous best scheme, RISE, are secure under our new definition.