International Association
for Cryptologic Research

While digital secret keys appear indispensable in modern cryptography and security, they also routinely constitute a main attack point of the resulting hardware systems. Some recent approaches have tried to overcome this problem by simply avoiding keys and secrets in vulnerable systems. To start with, physical unclonable functions (PUFs) have demonstrated how “classical keys”, i.e., permanently stored digital secret keys, can be evaded, realizing security devices that might be called “classically key-free”. Still, most PUFs induce certain types of physical secrets deep in the hardware, whose disclosure to adversaries breaks security as well. Examples include the manufacturing variations that determine the power-up states of SRAM PUFs, or the signal runtimes of Arbiter PUFs, both of which have been extracted from PUF-hardware in practice, breaking security. A second generation of physical security primitives, such a SIMPLs/PPUFs and Unique Objects, recently has shown promise to overcome this issue, however. Perhaps counterintuitively, they would enable completely “secret-free” hardware, where adversaries might inspect every bit and atom, and learn any information present in any form in the hardware, without being able to break security. This concept paper takes this situation as starting point, and categorizes, formalizes, and surveys the currently emerging areas of key-free and, more importantly, secret-free security. Our treatment puts keys, secrets, and their respective avoidance into the center of the currently emerging physical security methods. It so aims to lay the foundations for future, secret-free security hardware, which would be innately and provably immune against any physical probing and key extraction.

Event date: 19 August to 23 August 2019
Submission deadline: 6 May 2019
Notification: 6 June 2019

Event date: 7 April to 30 November 2019
Submission deadline: 30 June 2019

Event date: 4 December to 6 December 2019
Submission deadline: 29 August 2019
Notification: 21 October 2019

Applications are invited for 2x PhD studentships sponsored by the UK National Cyber Security Centre (NCSC) in the areas of: (1) Applying Deep Learning to Enhance Physical Unclonable Functions; and (2) Deep Learning for Total Network Defence.

ACADEMIC REQUIREMENTS: A minimum 2.1 honours degree or equivalent in Computer Science, Electrical and Electronic Engineering, Mathematics or closely related discipline is required. This is an NCSC-sponsored PhD studentship; therefore, only UK nationals are eligible for this funding. NCSC will be offering the student an opportunity to work more closely with them – e.g., via a short internship or attendance at technical meetings. As such, the recipient of this studentship will have to be appropriately security cleared by NCSC before they start their doctoral studies.

GENERAL INFORMATION: A GCHQ-sponsored PhD studentship provides funding for 3.5 years and commences Oct 2019. It covers approved tuition fees and a maintenance grant of approx.. £22,500 each year (tax-free). A further £5k of funding will also be available per annum for travel to conferences, collaborative partners, NCSC visits, etc.

To Apply, use the online application system available at: https://dap.qub.ac.uk/portal/

Closing date for applications: 31 May 2019

Contact: m.oneill AT ecit.qub.ac.uk

More information: https://www.qub.ac.uk/ecit/Education/PhDProjects/PhDResearchProjects2019/CSITCluster/

The position of Lecturer/Senior Lecturer of Cyber Security is responsible for undertaking research; teaching at undergraduate and postgraduate level including course coordination; research higher degree student supervision; and professional activities in the field of Cyber Security with a focus on cryptography and cyber security automation.

1. Cryptography position:–

We welcome applications from computer scientists with expertise in applied cryptography including but not limited to threshold cryptography, lightweight cryptography, post quantum cryptography, quantum key distribution and management, practical homomorphic encryption, cryptanalysis, data privacy-preserving techniques, and engineering of cryptographic applications according to international standards. Experts in other emerging cryptography research areas are also welcome to apply. Experience or an interest in engineering or standardizing industry-grade cryptographic solutions will be highly regarded. We seek to appoint a scientist with interest and experience in systems thinking and well versed in cryptographic and coding technologies.

2. Automation position:-

We welcome applications from computer scientists with expertise in cyber security autonomy and automation, covering areas including but not limited to exploit generation, reverse engineering, symbolic execution, program testing, fuzzing, vulnerability detection and mitigation, security information and event management. Experts with experience and interest in applying machine learning and AI planning to cyber security are also welcome to apply. Experience or an interest in engineering or standardizing industry-grade cyber security solutions will be highly regarded. We seek to appoint a scientist with interest and experience in systems thinking and well versed in vulnerability discovery and exploitation technologies.

This role is a full-time position; however flexible working arrangements may be negotiated. The University of Queensland values diversity and inclusion and actively encourages applications from those who bring diversity to the University.

Closing date for applications: 19 May 2019

Contact: ryan.ko AT uq.edu.au

More information: http://jobs.uq.edu.au/caw/en/job/507415/lecturersenior-lecturer-in-cyber-security-cryptographyautomation

The Information Security Group (ISG) at Royal Holloway University of London are looking for a full time permanent Professor/Reader (Chair/Distinguished or Full Professor) and three full time permanent lecturers (assistant professors).

The ISG is a full department within the university specialising in information/cyber security research and teaching and is one of the biggest specialist research and teaching groups in the UK. Details of the positions and more information about the ISG and Royal Holloway can be found at:

Professor/Reader: https://andersonquigley.com/digitalleaders/\"

Lecturers: https://jobs.royalholloway.ac.uk/vacancy.aspx?ref=0419-139

Additionally Royal Holloway is also looking for a head of Department for Computer Science and Head of Department in Media Arts (see https://andersonquigley.com/digitalleaders/ ).

Closing date for applications: 7 May 2019

Contact: Peter Komisarczuk

Head of Department/Director Information Security Group

Royal Holloway, University of London

Tel: +44 (0)1784443089

peter.komisarczuk (at) rhul.ac.uk

More information: https://jobs.royalholloway.ac.uk/vacancy.aspx?ref=0419-139

Event date: 10 June to 14 June 2019

Event date: 11 November to 13 November 2019
Submission deadline: 12 July 2019
Notification: 13 September 2019

Recently, the NIST launched a competition for lightweight cryptography and a large number of ciphers are expected to be studied and analyzed under this competition. Apart from the classical security, the candidates are desired to be analyzed against physical attacks. Differential Fault Analysis (DFA) is an invasive physical attack method for recovering key information from cipher implementations. Up to date, almost all the block ciphers have been shown to be vulnerable against DFA, while following similar attack patterns. However, so far researchers mostly focused on particular ciphers rather than cipher families, resulting in works that reuse the same idea for different ciphers.

In this article, we aim at bridging this gap, by providing a generic DFA attack method targeting Substitution-Permutation Network (SPN) based families of symmetric block ciphers. We provide an overview of the state-of-the-art of the fault attacks on SPNs, followed by generalized conditions that hold on all the ciphers of this design family. We show that for any SPN, as long as the fault mask injected before a non-linear layer in the last round follows a non-uniform distribution, the key search space can always be reduced. This shows that it is not possible to design an SPN-based cipher that is completely secure against DFA, without randomization. Furthermore, we propose a novel approach to find good fault masks that can leak the key with a small number of instances. We then developed a tool, called Joint Difference Distribution Table (JDDT) for pre-computing the solutions for the fault equations, which allows us to recover the last round key with a very small number of pairs of faulty and non-faulty ciphertexts. We evaluate our methodology on various block ciphers, including PRESENT-80, PRESENT-128, GIFT-64, GIFT-128, AES-128, LED-64, LED-128, Skinny-64-64, Skinny-128-128, PRIDE and PRINCE. The developed technique would allow automated DFA analysis of several candidates in the NIST competition.

Secure computation enables participating parties to jointly compute a function over their inputs while keeping them private. Secret sharing plays an important role for maintaining privacy during the computation. In most schemes, secret sharing over the same finite field is normally utilized throughout all the steps in the secure computation. A major drawback of this “uniform” approach is that one has to set the size of the field to be as large as the maximum of all the lower bounds derived from all the steps in the protocol. This easily leads to a requirement for using a large field which, in turn, makes the protocol inefficient. In this paper, we propose a “non-uniform” approach: dynamically changing the fields so that they are suitable for each step of computation. At the core of our approach is a surprisingly simple method to extend the underlying field of a secret sharing scheme, in a non-interactive manner, while maintaining the secret being shared. Using our approach, default computations can hence be done in a small field, which allows better efficiency, while one would extend to a larger field only at the necessary steps. As the main application of our technique, we show an improvement upon the recent actively secure protocol proposed by Chida et al. (Crypto’18). The improved protocol can handle a binary field, which enables XOR-free computation of a boolean circuit. Other applications include efficient (batch) equality check and consistency check protocols, which are useful for, e.g., password-based threshold authentication

We present a simple algorithm for Miller inversion for the reduced Tate pairing on supersingular elliptic curve of trace zero defined over the finite fields with q elements. Our algorithm runs with O((log q)^3) bit operations.

Oblivious RAM (ORAM) and private information retrieval (PIR) are classic cryptographic primitives used to hide the access pattern to data whose storage has been outsourced to an untrusted server. Unfortunately, both primitives require considerable overhead compared to plaintext access. For large-scale storage infrastructure with highly frequent access requests, the degradation in response time and the exorbitant increase in resource costs incurred by either ORAM or PIR prevent their usage. In an ideal scenario, a privacy-preserving storage protocols with small overhead would be implemented for these heavily trafficked storage systems to avoid negatively impacting either performance and/or costs. In this work, we study the problem of the best $\mathit{storage\ access\ privacy}$ that is achievable with only $\mathit{small\ overhead}$ over plaintext access.

To answer this question, we consider $\mathit{differential\ privacy\ access}$ which is a generalization of the $\mathit{oblivious\ access}$ security notion that are considered by ORAM and PIR. Quite surprisingly, we present strong evidence that constant overhead storage schemes may only be achieved with privacy budgets of $\epsilon = \Omega(\log n)$. We present asymptotically optimal constructions for differentially private variants of both ORAM and PIR with privacy budgets $\epsilon = \Theta(\log n)$ with only $O(1)$ overhead. In addition, we consider a more complex storage primitive called key-value storage in which data is indexed by keys from a large universe (as opposed to consecutive integers in ORAM and PIR). We present a differentially private key-value storage scheme with $\epsilon = \Theta(\log n)$ and $O(\log\log n)$ overhead. This construction uses a new oblivious, two-choice hashing scheme that may be of independent interest.

The WPA3 certification aims to secure Wi-Fi networks, and provides several advantages over its predecessor WPA2, such as protection against offline dictionary attacks and forward secrecy.

Unfortunately, we show that WPA3 is affected by several design flaws, and analyze these flaws both theoretically and practically. Most prominently, we show that WPA3's Simultaneous Authentication of Equals (SAE) handshake, commonly known as Dragonfly, is affected by password partitioning attacks. These attacks resemble dictionary attacks and allow an adversary to recover the password by abusing timing or cache-based side-channel leaks. Our side-channel attacks target the protocol's password encoding method. For instance, our cache-based attack exploits SAE's hash-to-curve algorithm.

The resulting attacks are efficient and low cost: brute-forcing all 8-character lowercase password requires less than 125$ in Amazon EC2 instances.

In light of ongoing standardization efforts on hash-to-curve, Password-Authenticated Key Exchanges (PAKEs), and Dragonfly as a TLS handshake, our findings are also of more general interest.

Finally, we discuss how to mitigate our attacks in a backwards-compatible manner, and explain how minor changes to the protocol could have prevented most of our attacks.

With Attribute-based Signatures (ABS) users can simultaneously sign messages and prove compliance of their attributes, issued by designated attribute authorities, with some verification policy. Neither signer's identity nor possessed attributes are leaked during the verification process, making ABS schemes a handy tool for applications requiring privacy-preserving authentication. Earlier ABS schemes lacked support for hierarchical delegation of attributes (across tiers of attribute authorities down to the signers), a distinct property that has made traditional PKIs more scalable and widely adoptable.

This changed recently with the introduction of Hierarchical ABS (HABS) schemes, where support for attribute delegation was proposed in combination with stronger privacy guarantees for the delegation paths (path anonymity) and new accountability mechanisms allowing a dedicated tracing authority to identify these paths (path traceability) and the signer, along with delegated attributes, if needed. Yet, current HABS construction is generic with inefficient delegation process resulting in sub-optimal signature lengths of order $O(k^{2}|\Psi|)$ where $\Psi$ is the policy size and $k$ the height of the hierarchy.

This paper proposes a direct HABS construction in bilinear groups that significantly improves on these bounds and satisfies the original security and privacy requirements. At the core of our HABS scheme is a new delegation process based on the length-reducing homomorphic trapdoor commitments to group elements for which we introduce a new delegation technique allowing step-wise commitments to additional elements without changing the length of the original commitment and its opening. While also being of independent interest, this technique results in shorter HABS keys and achieves the signature-length growth of $O(k|\Psi|)$ which is optimal due to the path-traceability requirement.

Cube attacks are an important type of key recovery attacks against stream ciphers. In particular, it is shown to be powerful against Trivium-like ciphers. Traditional cube attacks are experimental attacks which could only exploit cubes of size less than 40. At CRYPTO 2017, division property based cube attacks were proposed by Todo et al., and an advantage of introducing the division property to cube attacks is that large cube sizes which are beyond the experimental range could be explored, and so powerful theoretical attacks were mounted to many lightweight stream ciphers.

In this paper, we revisit the division property based cube attacks. There is an important assumption, called Weak Assumption, proposed in division property based cube attacks to support the effectiveness of key recovery. Todo et al. in CRYPTO 2017 said that the Weak Assumption was expected to hold for theoretically recovered superpolies of Trivium according to some experimental results on small cubes. In this paper, based on some new techniques to remove invalid division trails, some best key recovery results given at CRYPTO 2017 and CRYPTO 2018 on Trivium are proved to be distinguishers. First, we build a relationship between the bit-based division property and the algebraic degree evaluation on a set of active variables. Second, based on our algebraic point of view, we propose a new variant of division property which incorporates the distribution of active variables. Third, a new class of invalid division trails are characterized and new techniques based on MILP models to remove them are proposed. Hopefully this paper could give some new insights on accurately evaluating the propagation of the bit-based division property and also attract some attention on the validity of division property based cube attacks against stream ciphers.

It is known that information-theoretically secure computation can be done by using a deck of physical cards. In card-based protocols, shuffles, which covertly rearrange the order of cards according to a permutation chosen randomly, are the heaviest operations. Due to this, the number of shuffles in a protocol is desired to be small. However, as far as we know, there are no general-purpose protocols with a constant number of shuffles. In this paper, we construct a general-purpose protocol with a constant number of shuffles; surprisingly, just one (somewhat complicated) shuffle. This is achieved by introducing the garbled circuit methodology. Moreover, to make our shuffle simpler, we also develop a novel technique for aggregating several pile-scramble shuffles (which are efficiently implementable) into one pile-scramble shuffle. Consequently, we also construct a general-purpose protocol with two pile-scramble shuffles. Both techniques may lead to many other applications in this area.

We construct efficient, unconditional non-malleable codes that are secure against tampering functions computed by decision trees of depth $d = n^{1/4-o(1)}$. In particular, each bit of the tampered codeword is set arbitrarily after adaptively reading up to $d$ arbitrary locations within the original codeword. Prior to this work, no efficient unconditional non-malleable codes were known for decision trees beyond depth $O(\log^2 n)$.

Our result also yields efficient, unconditional non-malleable codes that are $\exp(-n^{\Omega(1)})$-secure against constant-depth circuits of $\exp(n^{\Omega(1)})$-size. Prior work of Chattopadhyay and Li (STOC 2017) and Ball et al. (FOCS 2018) only provide protection against $\exp(O(\log^2n))$-size circuits with $\exp(-O(\log^2n))$-security.

We achieve our result through simple non-malleable reductions of decision tree tampering to split-state tampering. As an intermediary, we give a simple and generic reduction of leakage-resilient split-state tampering to split-state tampering with improved parameters. Prior work of Aggarwal et al. (TCC 2015) only provides a reduction to split-state non-malleable codes with decoders that exhibit particular properties.

We introduce pRate, a novel reputation management scheme with strong security and privacy guarantees for the users and their reputation scores. The reputation scores are computed based on the (aggregated) number(s) of stars that users receive from their raters. pRate allows users to advertise privacy-friendly statements about their reputation when searching for potential transaction partners. Ratings can only be submitted by partners who have been initially authorised by the ratee and issued a rating token. The scheme is managed by a possibly untrusted reputation manager who can register users and assist ratees in updating their reputation scores, yet without learning these scores. In addition to ensuring the secrecy of the ratings, a distinctive feature of pRate over prior proposals, is that it hides the identities of raters and ratees from each other during the transaction and rating stages. The scheme is built from a number of efficient cryptographic primitives; its security is formally modeled and proven to hold under widely used assumptions on bilinear groups.

We prove an $\Omega(d \lg n/ (\lg\lg n)^2)$ lower bound on the dynamic cell-probe complexity of statistically $\mathit{oblivious}$ approximate-near-neighbor search ($\mathsf{ANN}$) over the $d$-dimensional Hamming cube. For the natural setting of $d = \Theta(\log n)$, our result implies an $\tilde{\Omega}(\lg^2 n)$ lower bound, which is a quadratic improvement over the highest (non-oblivious) cell-probe lower bound for $\mathsf{ANN}$. This is the first super-logarithmic $\mathit{unconditional}$ lower bound for $\mathsf{ANN}$ against general (non black-box) data structures. We also show that any oblivious $\mathit{static}$ data structure for decomposable search problems (like $\mathsf{ANN}$) can be obliviously dynamized with $O(\log n)$ overhead in update and query time, strengthening a classic result of Bentley and Saxe (Algorithmica, 1980).