International Association
for Cryptologic Research

Privacy protection and scalability are significant issues with blockchain. We propose an anonymous probabilistic payment under the general functionality for solving them. We consider the situation that several payers pay several payees through a tumbler. We have mediated the tumbler of the payment channel hub between payers and payees. Unlinkability means that the link, which payer pays which payee via the tumbler, is broken. A cryptographic puzzle plays a role in controlling the intermediation and execution of transactions. Masking the puzzle enables the payer and the payee to unlink their payments. The overview of the proposed protocol is similar to TumbleBit (NDSS 2017). We confirm the protocol realizes the ideal functionalities discussed in TumbleBit. The functionality required for our proposal is the hashed time lock contract that various cryptocurrencies use. This request is general, not restricted to any particular cryptocurrency. Our proposal includes a probabilistic payment. In probabilistic payment, one pays an ordinary mount with a certain probability. One pays a small amount as an expected value. One can run fewer transactions than a deterministic payment. It contributes scalability. We introduce a novel fractional oblivious transfer for probabilistic payment. We call it the ring fractional oblivious transfer (RFOT). RFOT is based on the ring learning with errors (RLWE) encryption. Our trick is based on the fact that an element of the ring is indistinguishable from the circular shifted element. We confirm that RFOT holds the properties of fractional hiding and binding presented in the DAM scheme (Eurocrypt 2017).

In modern distributed systems, an adversary’s limitations when corrupting subsets of servers may not necessarily be based on threshold constraints, but rather based on other technical or organizational characteristics in the systems. For example, it can be based on the operating systems they run, the cost of corrupting insiders in a sub-organization, et cetera. This means that the corruption patterns (and thus protection guarantees) are not based on the adversary being limited by a threshold, but on the adversary being limited by other constraints, in particular by what is known as a General Adversary Structure (GAS). GAS settings may come up in situations like large enterprises, computing and networking infrastructure of Internet Service Providers, data centers and cloud infrastructure, IT infrastructure of government agencies, computerized military systems, and critical infrastructure. We consider efficient secure multiparty computation (MPC) under such dynamically-changing GAS settings. During these changes, one desires to protect against and during corruption profile change, which renders some (secret sharing-based) encoding schemes underlying the MPC protocol more efficient than others when operating with the (currently) considered GAS. One of our contributions is a set of novel protocols to efficiently and securely convert back and forth between different MPC schemes for GAS; this process is often called share conversion. Specifically, we consider two MPC schemes, one based on additive secret sharing and the other based on Monotone Span Programs (MSP). The ability to efficiently convert between the secret sharing representations of these MPC schemes enables us to construct the first communication-efficient structure-adaptive proactive MPC protocol for dynamic GAS settings. By structure-adaptive, we mean that the choice of the MPC protocol to execute in future rounds after the GAS is changed (as specified by an administrative entity) is chosen to ensure communication-efficiency (the typical bottleneck in MPC). Furthermore, since such secure collaborative computing may be long-lived, we consider the mobile adversary setting, often called the proactive security setting. As our second contribution, we construct communication-efficient MPC protocols that can adapt to the proactive security setting. Proactive security assumes that at each (well defined) period of time the adversary corrupts different parties and over time may visit the entire system and corrupt all parties, provided that in each period it controls groups obeying the GAS constraints. In our protocol, the shares can be refreshed, meaning that parties receive new shares reconstructing the same secret, and some parties who lost their shares because of the reboot/resetting can recover their shares. As our third contribution, we consider another aspect of global long-term computations, namely, that of the dynamic groups. It is worth pointing out that such a setting with dynamic groups and GAS was not dealt with in existing literature on (proactive) MPC. In dynamic group settings, parties can be added and eliminated from the computation, under different GAS restrictions. We extend our protocols to this additional dynamic group settings defined by different GAS.

Cryptography is one of the basic phenomena of security systems. However, some of the widely used public key cryptography algorithms can be broken by using quantum computers. Therefore, many post-quantum cryptography algorithms are proposed in recent years to handle this issue. NTRU is one of the most important of these quantum-safe algorithms. Besides the importance of cryptography algorithms, the architecture where they are implemented is also essential. In this study, we developed an NTRU public key cryptosystem application and designed several processors to compare them in many aspects. We address two dierent architectures in this work. The RISC-V is chosen as it is the most lately version of classical RISC architecture. As competitor to this, we preferred transport triggered architecture (TTA) which oers high level customization and scalability. Details of all dierent implementations and the test results obtained with them are shared and discussed.

In digital world cryptographic algorithms protect sensitive information from intruder during communication. True random number generation is used for Cryptography algorithms as key value encryption and decryption process. To develop unbreakable algorithms key as one important parameter for Cryptography .We proposed DNA based True random number generation.DNA is deoxyribonucleic acid chemical molecule present in all living cells. DNA molecule consists of 4 nucleotides A-adenine,T-Thymine,G-Guanine and CCytosine. DNA molecules have uniqueness properties like Each person in the world distinguish based on DNA sequences and genes. The proposed algorithm pass NIST SP 800-22 test suite for DNA based true random number generation with highest Entropy,FFT,Block Frequency and Linear Complexity.

Gimli is a family of cryptographic primitives (both a hash function and an AEAD scheme) that has been selected for the second round of the NIST competition for standardizing new lightweight designs. The candidate Gimli is based on the permutation Gimli, which was presented at CHES 2017. In this paper, we study the security of both the permutation and the constructions that are based on it. We exploit the slow diffusion in Gimli and its internal symmetries to build, for the first time, a distinguisher on the full permutation of complexity 2^64 . We also provide a practical distinguisher on 23 out of the full 24 rounds of Gimli that has been implemented.

Next, we give (full state) collision and semi-free-start collision attacks on Gimli-Hash, reaching respectively up to 12 and 18 rounds. On the practical side, we compute a collision on 8-round Gimli-Hash. In the quantum setting, these attacks reach 2 more rounds. Finally, we perform the first study of linear trails in the permutation, and we propose differential-linear cryptanalysis that reach up to 17 rounds of Gimli.

In the implementation of post-quantum primitives, it is well known that all computations that handle secret information need to be implemented to run in constant time. Using the Fujisaki-Okamoto transformation or any of its different variants, a CPA-secure primitive can be converted into an IND-CCA secure KEM. In this paper we show that although the transformation does not handle secret information apart from calls to the CPA-secure primitive, it has to be implemented in constant time. Namely, if the ciphertext comparison step in the transformation is leaking side-channel information, we can launch a key-recovery attack. Several proposed schemes in round 2 of the NIST post-quantum standardization project are susceptible to the proposed attack and we develop and show the details of the attack on one of them, being FrodoKEM. It is implemented on the reference implementation of FrodoKEM, which is claimed to be secure against all timing attacks. Experiments show that the attack code is able to extract the secret key for all security levels using about \(2^{30}\) decapsulation calls.

Side-channel analysis and fault-injection attacks are known as serious threats to cryptographic hardware implementations and the combined protection against both is currently an open line of research. A promising countermeasure with considerable implementation overhead appears to be a mix of first-order secure Threshold Implementations and linear Error-Correcting Codes.

In this paper we employ for the first time the inherent structure of non-systematic codes as fault countermeasure which dynamically mutates the applied generator matrices to achieve a higher-order side-channel and fault-protected design. As a case study, we apply our scheme to the PRESENT block cipher that do not show any higher-order side-channel leakage after measuring 150 million power traces.

Loyalty programs in the form of punch cards that can be redeemed for benefits have long been a ubiquitous element of the consumer landscape. However, their increasingly popular digital equivalents, while providing more convenience and better bookkeeping, pose a considerable risk to consumer privacy. This paper introduces a privacy-preserving punch card protocol that allows firms to digitize their loyalty programs without forcing customers to submit to corporate surveillance. We also present a number of extensions that allow our scheme to provide other privacy-preserving customer loyalty features.

Compared to the best prior work, we achieve a 14x reduction in the computation and a 25x reduction in communication required to perform a "hole punch," a 62x reduction in the communication required to redeem a punch card, and a 394x reduction in the computation time required to redeem a card. Much of our performance improvement can be attributed to removing the reliance on pairings present in prior work, which has only addressed this problem in the context of more general loyalty systems. By tailoring our scheme to punch cards and related loyalty systems, we demonstrate that we can reduce communication and computation costs by orders of magnitude.

Protocols for secure Multi-Party Computation (MPC) can be classified according to the underlying communication model. Two prominent communication models considered in the literature are the synchronous and asynchronous models, which considerably differ in terms of the achievable security guarantees. Synchronous MPC protocols can achieve the optimal corruption threshold $n/2$ and allow every party to give input, but become completely insecure when synchrony assumptions are violated. On the other hand, asynchronous MPC protocols remain secure under arbitrary network conditions, but can tolerate only $n/3$ corruptions and parties with slow connections unavoidably cannot give input.

A natural question is whether there exists a protocol for MPC that can tolerate up to $t_s < n/2$ corruptions under a synchronous network and $t_a < n/3$ corruptions even when the network is asynchronous. We answer this question by showing tight feasibility and impossibility results. More specifically, we show that such a protocol exists if and only if $t_a + 2t_s < n$ and the number of inputs taken into account under an asynchronous network is at most $n-t_s$.

Timed-release encryption (TRE) makes it possible to send information ``into the future'' such that a pre-determined amount of time needs to pass before the information can be decrypted, which has found numerous applications. The most prominent construction is based on sequential squaring in RSA groups, proposed by Rivest et al. in 1996. Malavolta and Thyagarajan (CRYPTO'19) recently proposed an interesting variant of TRE called homomorphic time-lock puzzles (HTLPs). Here one considers multiple puzzles which can be independently generated by different entities. One can homomorphically evaluate a circuit over these puzzles to obtain a new puzzle. Solving this new puzzle yields the output of a circuit evaluated on all solutions of the original puzzles. While this is an interesting concept and enables various new applications, for constructions under standard assumptions one has to rely on sequential squaring.

We observe that viewing HTLPs as homomorphic TRE gives rise to a simple generic construction that avoids the homomorphic evaluation on the puzzles and thus the restriction of relying on sequential squaring. It can be instantiated based on any TLP, such as those based on one-way functions and the LWE assumption (via randomized encodings), while providing essentially the same functionality for applications. Moreover, it overcomes the limitation of the approach of Malavolta and Thyagarajan that, despite the homomorphism, one puzzle needs to be solved per decrypted ciphertext. Hence, we obtain a ``solve one, get many for free'' property for an arbitrary amount of encrypted data, as we only need to solve a single puzzle independent of the number of ciphertexts. In addition, we introduce the notion of incremental TLPs as a particularly useful generalization of TLPs, which yields particularly practical (homomorphic) TRE schemes. Finally, we demonstrate various applications by firstly showcasing their cryptographic application to construct dual variants of timed-release functional encryption and also show that we can instantiate previous applications of HTLPs in a simpler and more efficient way.

In this article, we propose GIFT-COFB, an Authenticated Encryption with Associated Data (AEAD) scheme, based on the GIFT lightweight block cipher and the COFB lightweight AEAD operating mode. We explain how these two primitives can fit together and the various design adjustments possible for performance and security improvements. We show that our design provides excellent performances in all constrained scenarios, hardware or software, while being based on a provably-secure mode and a well analysed block cipher.

Today's most compact zero-knowledge arguments are based on the hardness of the discrete logarithm problem and related classical assumptions. If one is interested in quantum-safe solutions, then all of the known techniques stem from the PCP-based framework of Kilian (STOC 92) which can be instantiated based on the hardness of any collision-resistant hash function. Both approaches produce asymptotically logarithmic sized arguments but, by exploiting extra algebraic structure, the discrete logarithm arguments are a few orders of magnitude more compact in practice than the generic constructions.

In this work, we present the first (poly)-logarithmic, potentially post-quantum zero-knowledge arguments that deviate from the PCP approach. At the core of succinct zero-knowledge proofs are succinct commitment schemes (in which the commitment and the opening proof are sub-linear in the message size), and we propose two such constructions based on the hardness of the (Ring)-Short Integer Solution (Ring-SIS) problem, each having certain trade-offs. For commitments to $N$ secret values, the communication complexity of our first scheme is $\tilde{O}(N^{1/c})$ for any positive integer $c$, and $O(\log^2 N)$ for the second. Both of these are a significant theoretical improvement over the previously best lattice construction by Bootle et al. (CRYPTO 2018) which gave $O(\sqrt{N})$-sized proofs.

In the setting of continual-leakage (CL) --- Brakerski \emph{et al.}, Dodis \emph{et al.}, FOCS 2010 --- the secret key of a cryptographic scheme evolves according to time periods; the adversary gets some bounded leakage function of its choice applied to the current secret key in each time period. This model necessitates a \emph{randomized} key update procedure, as otherwise the adversary can leak a future secret key bit by bit over time. Unfortunately, this is a major source of difficulty, for example in handling leakage on updates. On the other hand, the above reason why a randomized key update procedure is required is arguably unsatisfying, since in practice a leakage function will not continually compute the update procedure and leak a future key in whole.

Our goal is to provide a general security model for continual leakage with deterministic key updates, and constructions that improve in various respects on prior work. In fact, as described below we incorporate forward security into our model as well. For our basic security model we take an \emph{entropy-based} approach, leading to a model we call \emph{entropic continual leakage} (ECL). In the ECL model, the adversary is allowed to make a limited total number of leakage queries that, as in CL, can depend arbitrarily on other keys (in particular, we do not completely bar the leakage function from ``computing the update procedure''), but an \emph{unlimited} total number of what we call ``local'' leakage queries. The latter does not decrease computational entropy of other keys. Hence, in some sense, the local leakage queries do not compute the key update procedure. Another major benefit of allowing deterministic key updates is that we can more readily incorporate forward security (FS) in our constructions, recently pointed out by Bellare \emph{et al.} (CANS 2017) to be an important security hedge in this context. This is because techniques for achieving FS often require deterministic updates. Accordingly, we also introduce the FS+ECL model (which is in fact incomparable to the CL model). We target this enhanced model for our constructions and provide constructions of public-key encryption (based on non-interactive key exchange) and digital signatures (based on identification schemes) that improve over the assumptions or leakage rates of the FS+CL schemes of Bellare \emph{et al.}. These results demonstrate the feasibility of improved constructions in our more realistic model. Finally, as a result of independent interest, we present a public-key encryption scheme in the FS+CL model (with randomized update) that improves on both the assumptions and leakage rates compared to the scheme of Bellare \emph{et al}.

We present a new short zero-knowledge argument for the range proof and the arithmetic circuits without a trusted setup. In particular, the proof size of our protocol is the shortest of the category of proof systems with a trustless setup. More concretely, when proving a committed value is a positive integer less than 64 bits, except for negligible error in the $128$-bit security parameter, the proof size is $576$ byte long, which is of $85.7\%$ size of the previous shortest one due to B\"unz et al.~(Bulletproofs, IEEE Security and Privacy 2018), while computational overheads in both proof generation and verification are comparable with those of Bulletproofs, respectively. Bulletproofs is established as one of important privacy enhancing technologies for distributed ledger, due to its trustless feature and short proof size. In particular, it has been implemented and optimized in various programming languages for practical usages by independent entities since it proposed. The essence of Bulletproofs is based on the logarithmic inner product argument with no zero-knowledge. In this paper, we revisit Bulletproofs from the viewpoint of the first sublinear zero-knowledge argument for linear algebra due to Groth~(CRYPTO 2009) and then propose Bulletproofs+, an improved variety of Bulletproofs. The main ingredient of our proposal is the zero-knowledge weighted inner product argument (zk-WIP) to which we reduce both the range proof and the arithmetic circuit proof. The benefit of reducing to the zk-WIP is a minimal transmission cost during the reduction process. Note the zk-WIP has all nice features of the inner product argument such as an aggregating range proof and batch verification.

We provide a simple and complete proof of the famous Pi&#8853;Pj Theorem in the particular case where &#958;max=2. This Theorem gives a lower bound for the number of solutions of simple linear systems of equations in the case where all the variables have to be pairwise distinct. Such systems often occur in cryptographic proofs of security, and this particular Theorem can be used to prove that the function x&#8614;P(0||x)&#8853;P(1||x) is an optimally secure pseudorandom function when P is a uniformly random permutation.

Event date: 14 June to 17 June 2021
Submission deadline: 5 February 2021
Notification: 5 April 2021

About be-ys

Be-ys creates and monitors digital solutions for sensitive data processing in demanding business sectors such as healthcare and banking.
We are the national leader in data security, which is expanding internationally and deploying its solutions using state-of-the-art technologies.
We are now looking for new talents to strengthen our leading position and continue bringing innovation to the market.

Job Description

Our Be ys Pay subsidiary has created worldwide payment solutions. Our aim is to develop disruptive technologies for bank payment systems with smart card, mobile device and Blockchain. As part of its development, we are looking for a Software Developer for Payment Systems.
As part of an expert team dedicated to the payment technology, smart card, blockchain, cryptography and cryptography business sectors, your main tasks will be to develop products in C, C++, Java and NodeJS languages for smart card personalization, payment transaction authorization, token generation/validation and wallets for mobile devices.
You will be responsible for the development and implementation of algorithms, protocols and applications for PC or mobile devices for smart card issuance, as well as the development of solutions for the validation and generation of tokens for banking payment systems.

Profile description

• You have a 5-year degree in engineering, development and/or crypto
• You have an excellent knowledge of C, C++, Java and cryptography.
• Knowledge of payment technology with EMV standard and Blockchain would be a plus.
• You enjoy working as part of a team and working collaboratively in an agile mode.
• You are autonomous, proactive and have an interest in experimenting.
• You like innovation and enjoy working in a constantly changing environment.
• You must be fluent in English (written and spoken).

Closing date for applications:

Contact: Above all, we are looking for potential. We believe that passion for the job and skills are the key to a successful employee.
We transform your energy into talent.
To apply, please send your resume to: recrutement@almerys.com

Securing components for the IoT market, as well as critical cyberphysical infrastructures, requires analyzing their vulnerabilities and defining hardware and software countermeasures at the fair cost. The increasing complexity of the processors and the applications they run means that the software fault models (such as instruction skips, or instruction replacement) usually used to analyze the vulnerability of their code are no longer sufficient to express the diversity of faulty behaviors in modern architectures [1]. Indeed, architecture designers have progressively added many complex hardware blocks (such as pipeline, cache memory, branch prediction, or speculative execution) to processors in order to optimize program execution. At the same time, fault injection techniques are constantly progressing (e.g., localized ElectroMagnetic or laser attacks, glitch injection attacks) allowing today higher-order injections (both multi-temporal and multi-spatial). Faced with these attacks, designers must implement countermeasures to detect or mask the effects of injected faults. These countermeasures can be implemented at the hardware level (e.g., duplication of elements, error correcting codes, isolation mechanisms) or at the software level (e.g., duplication of instructions or algorithms, insertion of security tests, signature verification). The design and validation of these countermeasures requires a realistic representation of the effects of faulty attacks (fault model) at the hardware and/or software level. The difficulties encountered are then: (1) the relevance of the fault models: do these fault models correctly represent the effects that an attacker can generate on a target processor? (2) the adequacy of countermeasures: do the countermeasures effectively protect the system, are they oversized and therefore too costly? (3) the link between software and hardware countermeasures: how to combine software and hardware countermeasures efficiently and at the fair cost, how to link the different levels for fault modeling? The CLAM project and the thesis that we propose aim to answer these questions by associating 3 French laboratories with complementary specialties.

Closing date for applications:

Contact: vincent.beroulle(at)lcis.grenoble-inp.fr; paolo.maistri(at)univ-grenoble-alpes.fr

More information: https://lcis.grenoble-inp.fr/medias/fichier/clam-thesis-subject-lcis-valence-en-_1592239520450-pdf?ID_FICHE=559219&INLIN

The Department of Information Technology at Uppsala University invites applications for an Associate Professor in Computer Science with specialization in Cybersecurity The department hosts many successful research efforts on different aspects of cybersecurity, which have attracted a significant amount of external funding. We are now in the process to establish cybersecurity as a strong and visible area in research and teaching. The holder of the position is expected to develop a teaching and research profile in cybersecurity, as well as to take leadership responsibilities in cybersecurity activities within the department. Application Deadline: June 22.

Closing date for applications:

Contact: Christian Rohner (christian.rohner@it.uu.se)

More information: https://uu.se/en/about-uu/join-us/details/?positionId=325568

The new-age processor is going to require hardware-oriented solutions as a primary design criterion for the security against threats. Alternative computational architectures proposed in recent years drive this idea by the inclusion of multi-value logic operations. The realization of multi-value logic gates and testing the advantages of polymorphic inputs and outputs of a circuit, however, remains elusive due to the existing technology gap. In this project, we put forward a new logic-locking framework that will allow us to incorporate multi-value and multi-layer logic with existing CMOS-based logic-locking architectures. Enabling future-generation processors with BioNanoLock is the prime target of the project with small (10-100 logic gates) to medium-sized (100-10000 logic gates) circuits as an intermediate goal. We also envision developing heterogeneous integrated systems for secure information processing in the long-term. In BioNanoLock, an encoded DNA sequence acts as a secret ‘biological activation-key’. This key is molecularly recognized as a unique and secret pattern of key-gates (called biological key-gates) or activates them. This, in turn, enables the CMOS-based key-gates in the logic-locked circuit with the appropriate key value. Different voltage-levels in the multi-valued logic define the “on” or “off” state of the key-gates, thereby adding another level of ambiguity for an attacker and making it harder for the attacker to unlock the circuit. Moving away from the classical CMOS-based techniques for logic locking, the BioNanoLock project enables the researchers to delve into novel logic locking techniques. The project also provides opportunities to map the new logic locking paradigms and attack methodologies to a different class of problems in the complexity theory. As novel simulation methodologies are unexplored in the interdisciplinary domain, the project provides ample opportunities for research and innovation.

Closing date for applications:

Contact: Dr. Farhad Merchant (farhad.merchant@ice.rwth-aachen.de)

More information: https://www.ice.rwth-aachen.de/institute/jobs/job-offer-research-assistant-phd-student-for-bionanolock-project-1/