Tight Security Research Articles

Ultra Lightweight Multiple-Time Digital Signature for the Internet of Things Devices

Digital signatures are basic cryptographic tools to provide authentication and integrity in the emerging ubiquitous systems in which resource-constrained devices are expected to operate securely and efficiently. However, existing digital signatures might not be fully practical for such resource-constrained devices (e.g., medical implants) that have energy limitations. Some other computationally efficient alternatives (e.g., one-time/multiple-time signatures) may introduce high memory and/or communication overhead due to large private key and signature sizes. In this paper, our contributions are two-fold: First, we develop a new lightweight multiple-time digital signature scheme called Signer Efficient Multiple-time Elliptic Curve Signature ( <inline-formula><tex-math notation="LaTeX">$\mathtt {SEMECS}{}$</tex-math></inline-formula> ), which is suitable for resource-constrained embedded devices. <inline-formula><tex-math notation="LaTeX">$\mathtt {SEMECS}{}$</tex-math></inline-formula> achieves optimal signature and private key sizes for an EC-based signature <i>without</i> requiring any EC operation (e.g., EC scalar multiplication or addition) at the signer. We prove <inline-formula><tex-math notation="LaTeX">$\mathtt {SEMECS}{}$</tex-math></inline-formula> is secure (in random oracle model) with a tight security reduction. Second, we fully implemented <inline-formula><tex-math notation="LaTeX">$\mathtt {SEMECS}{}$</tex-math></inline-formula> on 8-bit AVR microprocessor with a comprehensive energy consumption analysis and comparison. Our experiments confirm up to 19× less battery-consumption for <inline-formula><tex-math notation="LaTeX">$\mathtt {SEMECS}{}$</tex-math></inline-formula> as compared to its fastest (full-time) counterpart, SchnorrQ, while offering significant performance advantages over its multiple-time counterparts in various fronts. We open-source our implementation for public testing and adoption.

A highly secure stream cipher based on analog-digital hybrid chaotic system

In recent decades, an avalanche of chaos-based cryptosystems have been proposed for information security. Most of these systems are not immune to the dynamical degradation of digital chaos and many have been shown to suffer from a lack of security. In this paper, a stream cipher system based on an analog–digital hybrid chaotic system is presented. The hybrid model can construct digital chaotic maps without degeneration and guarantee synchronization of analog chaotic systems for successful decryption. Moreover, focusing on the characteristics of low-dimensional chaotic maps, a modified three-dimensional Logistic map is proposed to improve the weaknesses of uneven distribution, low complexity and limited parameter space. Combining the three-dimensional Logistic map and the hybrid model, the proposed stream cipher has advantages of huge key space, virtually infinite cycle length and tight security. In particular, it is not affected by the dynamical degradation. Performance and security analyses indicate that the proposed stream cipher is highly resistant to various chaos-based attacks and cryptanalytic attacks.

Generic construction for tightly-secure signatures from discrete log

Tightly secure signature plays a significant role in the research of cryptography and has been studied extensively in the literature. In this paper, we present a generic construction for tightly-secure signatures from the discrete log (DL) assumption in the existential-unforgeability against key only attacks (EUF-KOA) security model, where the adversary is allowed to obtain only the public key, but not any sample signature. Moreover, the generic construction can also be extended into the multi-user setting with corruptions (MU-C) model. Roughly speaking, given any signature scheme, we can efficiently convert it into a signature scheme that features tight security under the DL assumption in the MU-EUF-KOA-C security model with random oracles. Our transformation shows it is easy to construct a DL-equivalent signature in the EUF-KOA security model, although many known DL-based signatures are not equivalent to DL. If the given signature scheme is key-re-randomizable, the transformed scheme is also key-re-randomizable. Hence, our result provides a supplement to Bader et al.'s work (EUROCRYPT 2016).

A Pairing-Free Identity-Based Identification Scheme with Tight Security Using Modified-Schnorr Signatures

The security of cryptographic schemes is proven secure by reducing an attacker which breaks the scheme to an algorithm that could be used to solve the underlying hard assumption (e.g., Discrete Logarithm, Decisional Diffie–Hellman). The reduction is considered tight if it results in approximately similar probability bounds to that of solving the underlying hard assumption. Tight security is desirable as it improves security guarantees and allows the use of shorter parameters without the risk of compromising security. In this work, we propose an identity-based identification (IBI) scheme with tight security based on a variant of the Schnorr signature scheme known as TNC signatures. The proposed IBI scheme enjoys shorter parameters and key sizes as compared to existing IBI schemes without increasing the number of operations required for its identification protocol. Our scheme is suitable to be used for lightweight authentication in resource-constrained Wireless Sensor Networks (WSNs) as it utilizes the lowest amount of bandwidth when compared to other state-of-the-art symmetric key lightweight authentication schemes. Although it is costlier than its symmetric key counterparts in terms of operational costs due to its asymmetric key nature, it enjoys other benefits such as decentralized authentication and scalable key management. As a proof of concept to substantiate our claims, we perform an implementation of our scheme to demonstrate its speed and memory usage when it runs on both high and low-end devices.

Hybrid encryption using playfair and RSA cryptosystems

The security is demanded to transport important data over the network. In this work a hybrid encryption depending on playfair cipher and RSA algorithm is proposed to give more confidentially and get rid of the defects of the two methods. The first cipher text is obtained by playfair cipher by using (812) expanded key matrix that is filled by decimal ASCII characters of Alphabets, numbers and common characters of ASCII table while the final cipher text is obtained by RSA cryptosystem by applying it for blocks of two characters. The proposed hybrid encryption avoids to take large numbers in RSA algorithm and performs complex operations that need a long time to do. The proposed hybrid cipher is tight security that is difficult to analyze and detect from hackers and intruders.

Security of Personal Data in Social Networks

The Information Society has created different possibilities for remote access to distributed information resources and communications between users (virtual environments, cloud services, social media, etc.). With millions of users’ data (or billions, in the case of Facebook) floating around the web, the need for tight security from social media platforms is obvious. The wide age range and technology experience level of social media users makes security management even more complex. A social platform needs to not only combat hackers, but also has to protect users whose personal security practices might be elementary.

On Length Independent Security Bounds for the PMAC Family

At FSE 2017, Gaži et al. demonstrated a pseudorandom function (PRF) distinguisher (Gaži et al., ToSC 2016(2)) on PMAC with Ω(lq2/2n) advantage, where q, l, and n, denote the number of queries, maximum permissible query length (in terms of n-bit blocks), and block size of the underlying block cipher. This, in combination with the upper bounds of Ο(lq2/2n) (Minematsu and Matsushima, FSE 2007) and Ο(qσ/2n) (Nandi and Mandal, J. Mathematical Cryptology 2008(2)), resolved the long-standing problem of exact security of PMAC. Gaži et al. also showed that the dependency on l can be dropped (i.e. O(q2/2n) bound up to l ≤ 2n/2) for a simplified version of PMAC, called sPMAC, by replacing the Gray code-based masking in PMAC with any 4-wise independent universal hash-based masking. Recently, Naito proposed another variant of PMAC with two powering-up maskings (Naito, ToSC 2019(2)) that achieves l-free bound of O(q2/2n), provided l ≤ 2n/2. In this work, we first identify a flaw in the analysis of Naito’s PMAC variant that invalidates the security proof. Apparently, the flaw is not easy to fix under the existing proof setup. We then formulate an equivalent problem which must be solved in order to achieve l-free security bounds for this variant. Second, we show that sPMAC achieves O(q2/2n) bound for a weaker notion of universality as compared to the earlier condition of 4-wise independence. Third, we analyze the security of PMAC1 (a popular variant of PMAC) with a simple modification in the linear combination of block cipher outputs. We show that this simple modification of PMAC1 has tight security O(q2/2n) provided l ≤ 2n/4. Even if l &lt; 2n/4, we still achieve same tight bound as long as total number of blocks in all queries is less than 22n/3.

Secured Novel Lightweight IoT End Device Architecture using Confidentiality, Integrity, Authenticity &amp; Availability based tight security approach

IoT end devices essential security parameters are Confidentiality, Integrity, Authenticity and Availability(CIAA). Breach of any of these security parameters means compromise with security thus collapsing the device. Even partial breach in security refers to loop holes in security hence unsecure IoT end device. Due to wearable nature of IoT end devices implementing security and maintaining lightweight is a challenge. Conventional security algorithms incur memory and processing overheads in wearable IoT end devices therefore lightweight security algorithms is compulsory. The existing architectures merely consider security enhancement using conventional security algorithm without focusing on lightweight therefore this paper analyzes existing IoT end device architectures and concludes that all are overarchitectured. Due to over- architecture the components of existing architectures are more visible to the external world and invites more attacks hence unsecured. On the other hand lightweight IoT end device resources ensure less complexity hence less internal bugs, less attack surface area, less visibility to external world thus more secure.&#x0D; Mandatory security requirements in wearable IoT end devices are still an extensive research issue. Therefore this paper focuses on mandatory boot process security requirements, software security requirements and security requirements during communication. Our proposed architecture is implemented over ESP32 microcontroller with the application of Arduino IDE. Lightweight secured internet of things (SIT) algorithm was implemented for lightweight CIAA due to light security requirements in wearable devices. Finally this paper compares the latest lightweight and secure architecture with the proposed lightweight and secure architecture and concludes that proposed architecture is robust in terms of lightweight and security.

Adaptively secure lattice-based revocable IBE in the QROM: compact parameters, tight security, and anonymity

Adaptively secure lattice-based revocable IBE in the QROM: compact parameters, tight security, and anonymity

On the Tight Security of TLS 1.3: Theoretically Sound Cryptographic Parameters for Real-World Deployments

We consider the theoretically sound selection of cryptographic parameters, such as the size of algebraic groups or RSA keys, for TLS 1.3 in practice. While prior works gave security proofs for TLS 1.3, their security loss is quadratic in the total number of sessions across all users, which due to the pervasive use of TLS is huge. Therefore, in order to deploy TLS 1.3 in a theoretically sound way, it would be necessary to compensate this loss with unreasonably large parameters that would be infeasible for practical use at large scale. Hence, while these previous works show that in principle the design of TLS 1.3 is secure in an asymptotic sense, they do not yet provide any useful concrete security guarantees for real-world parameters used in practice. In this work, we provide a new security proof for the cryptographic core of TLS 1.3 in the random oracle model, which reduces the security of TLS 1.3 tightly (that is, with constant security loss) to the (multi-user) security of its building blocks. For some building blocks, such as the symmetric record layer encryption scheme, we can then rely on prior work to establish tight security. For others, such as the RSA-PSS digital signature scheme currently used in TLS 1.3, we obtain at least a linear loss in the number of users, independent of the number of sessions, which is much easier to compensate with reasonable parameters. Our work also shows that by replacing the RSA-PSS scheme with a tightly secure scheme (e.g., in a future TLS version), one can obtain the first fully tightly secure TLS protocol. Our results enable a theoretically sound selection of parameters for TLS 1.3, even in large-scale settings with many users and sessions per user.

Revisiting NIZK-Based Technique for Chosen-Ciphertext Security: Security Analysis and Corrected Proofs

Non-interactive zero-knowledge (NIZK) proofs for chosen-ciphertext security are generally considered to give an impractical construction. An interesting recent work by Seo, Abdalla, Lee, and Park (Information Sciences, July 2019) proposed an efficient semi-generic conversion method for achieving chosen-ciphertext security based on NIZK proofs in the random oracle model. The recent work by Seo et al. demonstrated that the semi-generic conversion method transforms a one-way (OW)-secure key encapsulation mechanism (KEM) into a chosen-ciphertext secure KEM while preserving tight security reduction. This paper shows that the security analysis of the semi-generic conversion method has a flaw, which comes from the OW security condition of the underlying KEM. Without changing the conversion method, this paper presents a revised security proof under the changed conditions that (1) the underlying KEM must be chosen-plaintext secure in terms of indistinguishability and (2) an NIZK proof derived from the underlying KEM via the Fiat–Shamir transform must have the properties of zero-knowledge and simulation soundness. This work extended the security proof strategy to the case of identity-based KEM (IBKEM) and also revise the security proof for IBKEM of previous method by Seo et al. Finally, this work gives a corrected security proof by applying the new proofs to several existing (IB)KEMs.

Impossibility on the Schnorr Signature from the One-More DL Assumption in the Non-Programmable Random Oracle Model

The Schnorr signature is one of the representative signature schemes and its security was widely discussed. In the random oracle model (ROM), it is provable from the DL assumption, whereas there is negative circumstantial evidence in the standard model. Fleischhacker, Jager, and Schröder showed that the tight security of the Schnorr signature is unprovable from a strong cryptographic assumption, such as the One-More DL (OM-DL) assumption and the computational and decisional Diffie-Hellman assumption, in the ROM via a generic reduction as long as the underlying cryptographic assumption holds. However, it remains open whether or not the impossibility of the provable security of the Schnorr signature from a strong assumption via a non-tight and reasonable reduction. In this paper, we show that the security of the Schnorr signature is unprovable from the OM-DL assumption in the non-programmable ROM as long as the OM-DL assumption holds. Our impossibility result is proven via a non-tight Turing reduction.

Ensuring Quality Safety in Schools: A Participatory Action Research Approach

The focus of this article is on the quality safety in Schools. Although safety in schools is a worldwide problem, in South Africa this seems to be getting worse for they are broken into, vandalized and set alight in vast majority. Taking a heed to around 1600 number of schools robbed, vandalized and torched during this frustrating and terrifying period of COVID -19, one would agree that schools are not protected. People seemed to have lost ethics and ownership towards schools. Schools appeared to be the safest place as well as conducive for study in the previous decades. Safety school promotes social and creative learning. Schools are robbed their groceries, equipments including computers and other paraphernalia for learning and teaching support. On the 10th July 2020, four schools in Limpopo Province had been broken into and all groceries were robbed at a gun point.&#x0D; Taking a number of instances into consideration, which occurred before horrifying situation of Covid-19, one would see a need for an investigation. Although schools are advised to establish tight and quality security fence, school equipments and groceries are still not safe. There is a variety of literature which focused on the roles of teachers, administrators and students in creating safe schools. For this study, the researcher focused on the role of Community towards ensuring quality safety in school as a Community resource. Therefore it is the Community’s obligation to ensure quality safety in Schools. Community needs to develop strategies to ensure safety in Schools for their children. In this study, the researcher established a model which is Community Support Team versus School Support Team.&#x0D; Therefore the researcher adopted a Participatory Action Research Approach to empower Community to strategize for ensuring quality safety in Schools. The researcher employed qualitative technique to collect data from the community members around four selected schools in a rural area.

A Tightly Secure DDH-based Multisignature with Public-Key Aggregation

From the birth of the blockchain technology, multisignatures attract much attention as a tool for handling blockchain transactions. Concerning the application to the blockchain, multisignatures with public-key aggregation, which can compress public keys of signers to a single public key, is preferable to the standard multisignature because the public keys and the signature used in a transaction are stored to verify the transaction later. Several multisignature schemes with public key aggregation are proposed, however, there are no known schemes having a tight security reduction. We propose a first multisignature with public-key aggregation whose security is proven to be tightly secure under the DDH assumption in the random oracle model. Our multisignature is based on the DDH-based multisignature by Le, Yang, and Ghorbani, however, our security proof is different from theirs. The idea of our security proof originates from another DDH-based multisignature by Le, Bonnecaze, and Gabillon whose security proof is tightly one. By tailoring their security proof to a setting which admits the public-key aggregation, we can prove the tight security of our multisignature.

Improved RSA lossy trapdoor function and applications

Kakvi and Kiltz (EUROCRYPT'12) proposed the first tight security reduction for RSA full domain hash signature scheme (RSA-FDH) with public exponent e < N1/4 in the random oracle (RO) model, and they left an open problem which called for a tightly secure RSA-FDH for N1/4 < e < N. In this paper, we consider the improved RSA (iRSA) trapdoor functions, introduced by Cao (Science in China'01), are functions that the security can be strictly proved to be equivalent to the factoring. We show that iRSA-FDH has a tight security reduction for e < N. Technically we construct iRSA lossy trapdoor functions, and then we apply the lossiness of the iRSA trapdoor functions to obtain tight security reductions for iRSA-FDH in the RO model. Finally, we propose a tightly secure blind signature scheme based on our iRSA lossy trapdoor functions in the RO model.

Tighter Security Proofs for GPV-IBE in the Quantum Random Oracle Model

Tighter Security Proofs for GPV-IBE in the Quantum Random Oracle Model

Applicability of Squeezed- and Coherent-State Continuous-Variable Quantum Key Distribution over Satellite Links.

We address the applicability of quantum key distribution with continuous-variable coherent and squeezed states over long-distance satellite-based links, considering low Earth orbits and taking into account strong varying channel attenuation, atmospheric turbulence and finite data ensemble size effects. We obtain tight security bounds on the untrusted excess noise on the channel output, which suggest that substantial efforts aimed at setup stabilization and reduction of noise and loss are required, or the protocols can be realistically implemented over satellite links once either individual or passive collective attacks are assumed. Furthermore, splitting the satellite pass into discrete segments and extracting the key from each rather than from the overall single pass allows one to effectively improve robustness against the untrusted channel noise and establish a secure key under active collective attacks. We show that feasible amounts of optimized signal squeezing can substantially improve the applicability of the protocols allowing for lower system clock rates and aperture sizes and resulting in higher robustness against channel attenuation and noise compared to the coherent-state protocol.

COVID 19 - CHALLENGES, ECONOMIC PROBLEMS

The article is focused on problems in the Georgian economy caused by the new coronavirus epidemic. The current implementation of the state budget of Georgia for 2020 has been analyzed, attention has been drawn to the difficulties of both tax and total revenue performance. The main focus is on the effectiveness of business support measures and the transparency and legality of spending money. Measures have been taken on the operative elaboration and implementation of the relevant micro-fiscal policy, in response to the shocks in demand-supply. Coronavirus has caused many problems in the world economy. The world economy fell by 7.5% in the United States on March 9, which has not happened on Wall Street since 2008 global economic crisis. Of course, the influence of Coronavirus on the Georgia’s economy is severe, and the country is trying to deal with it in every possible way. If we analyze the current state budget execution this year, it can be seen that the current state budget for 2020 has been implemented in the first quarter. However, we should not expect the second quarter of the state budget for the same year, as this trend is already visible in April and May. The problems will be reflected in May, both in terms of tax revenues and total revenues as well, which is expected to double the state budget deficit of 2.5%, which means a complete failure of the two quarters. It can be said that the shock of the economy that accompanies coronavirus is quite strange and it affects to the supply and demand at the same time. We see negative risks on the supply side, which is reflected in the high cost of doing business, the demand will decrease as for increased uncertainty, tighter security measures and restrictions on free movement, as a result, the ability of consumers to spend their own money will be reduced. Experience has shown that 1/3 of the economic losses will be caused by direct losses: job cuts, quarantine and etc. 2/3 of economic losses will be indirect - which will be related to the decrease in consumer confidence, changes in the behavior of business entities, as well as the tightening of access to credit resources. It can be said that the global financial market is now more stable than it was before the 2008 crisis, but the main challenge in the current situation is still to manage uncertainty. In such a situation, it is inevitable that the funds from the budget will be prioritized for health care, so that the health care of the citizens not to be hindered. It seems inevitable for us to resolve the demand – to develop appropriate microfiscal policies in response to the shocks in supply. It is welcome that the European Investment Bank supports Georgia in the fight against the new coronavirus, which is to support Georgian business, support the health care system and accelerate the implementation of existing projects. The World Bank provided $ 15 billion quick and instant assistance to address the first challenges of COVID-19, this was mainly in the field of health and social care. The World Bank is currently working on three financial assistance packages: 1. To assist the government in responding to health and social protection challenges, 2. Substantiation will be provided to the state budget to reduce the expected deficit, 3. The World Bank intends to help small and medium-sized businesses to restore jobs and develop the economy, with a particular focus on affected sectors such as tourism, the first phase shall be completed by the end of April, which will be followed consistently. The World Bank has highlighted such an important circumstance as the inevitability of a zoological recession, which will be followed by a slowdown in economic growth, which in the case of Georgia will be 4% (which is significant to consider). According to the government›s decision, 2 billion GEL has been allocated for direct assistance to the economy, in order to provide emergency financial and material assistance to a number of different categories of affected citizens. Particular attention is paid to operative execution and control of measures envisaged in the concrete plan of economic stimulus and the anti-crisis plan of the government.

Selected Terrorist Attacks in Civil Aviaton in the Early Part of the 21st Century

Developments in transport, the world's geopolitical order and technical innovations at the beginning of the millennium have also brought the real threat of terrorism back to civil aviation. The biggest catastrophe was the terrorist attacks of September 11, 2001 in the USA. Following this event, global terrorism became a much-discussed issue in today's world, while current threats have motivated significant improvements and tighter security in civil aviation in all developed countries around the world.

The radiologist empowerment through virtual multidisciplinary tumor boards: The commitment of oncologic care during COVID-19 pandemic

• Implementing a virtual tumor board program should represent a feasible goal for every health-care provider pursuing clinical excellence. • Even in time of COVID-19, the multidisciplinary commitment to oncologic care should remain imperative, as cancer may not forgive delays. • Working daily with advanced computer technologies, radiologists should lead virtual multidisciplinary tumor boards by present key images.