Cryptography

22 pages, 854 KiB

Open AccessArticle

Practical and Provably Secure Distributed Aggregation: Verifiable Additive Homomorphic Secret Sharing

by Georgia Tsaloli, Gustavo Banegas and Aikaterini Mitrokotsa

Cryptography 2020, 4(3), 25; https://doi.org/10.3390/cryptography4030025 - 21 Sep 2020

Cited by 10 | Viewed by 4314

Often clients (e.g., sensors, organizations) need to outsource joint computations that are based on some joint inputs to external untrusted servers. These computations often rely on the aggregation of data collected from multiple clients, while the clients want to guarantee that the results [...] Read more.

Often clients (e.g., sensors, organizations) need to outsource joint computations that are based on some joint inputs to external untrusted servers. These computations often rely on the aggregation of data collected from multiple clients, while the clients want to guarantee that the results are correct and, thus, an output that can be publicly verified is required. However, important security and privacy challenges are raised, since clients may hold sensitive information. In this paper, we propose an approach, called verifiable additive homomorphic secret sharing (VAHSS), to achieve practical and provably secure aggregation of data, while allowing for the clients to protect their secret data and providing public verifiability i.e., everyone should be able to verify the correctness of the computed result. We propose three VAHSS constructions by combining an additive homomorphic secret sharing (HSS) scheme, for computing the sum of the clients’ secret inputs, and three different methods for achieving public verifiability, namely: (i) homomorphic collision-resistant hash functions; (ii) linear homomorphic signatures; as well as (iii) a threshold RSA signature scheme. In all three constructions, we provide a detailed correctness, security, and verifiability analysis and detailed experimental evaluations. Our results demonstrate the efficiency of our proposed constructions, especially from the client side. Full article

(This article belongs to the Special Issue Techniques and Protocols to Preserve and Enhance Privacy)

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n clients outsourcing the joint addition of their joint inputs to m servers. Full article ">Figure 2
Time for PartialEval and PartialProof in our constructions. (a) Time for PartialEval and PartialProof in VAHSS-HSS. (b) Time for PartialEval and PartialProof in VAHSS-LHS. (c) Time for PartialEval and PartialProof in VAHSS-TSS. Full article ">Figure 3
Time for FinalProof in our constructions. (a) Time for the FinalProof algorithm in VAHSS-HSS. (b) Time for the FinalProof algorithm in VAHSS-LHS. (c) Time for the FinalProof algorithm in VAHSS-TSS. Full article ">Figure 4
Time for running Verify for each of our constructions. (a) Time for the Verify algorithm in VAHSS-HSS. (b) Time for the Verify algorithm in VAHSS-LHS. (c) Time for the Verify algorithm in VAHSS-TSS. Full article ">Figure 5
Bandwidth per serve and per client in bytes using VAHSS-HSS. Full article ">Figure 6
Bandwidth per serve and per client in bytes using VAHSS-LHS. Full article ">Figure 7
Bandwidth required per server and per client in bytes using VAHSS-TSS. Full article ">

16 pages, 984 KiB

Open AccessArticle

Chaotic Quantum Key Distribution

by Noah Cowper, Harry Shaw and David Thayer

Cryptography 2020, 4(3), 24; https://doi.org/10.3390/cryptography4030024 - 31 Aug 2020

Cited by 4 | Viewed by 3908

Abstract

The ability to send information securely is a vital aspect of today’s society, and with the developments in quantum computing, new ways to communicate have to be researched. We explored a novel application of quantum key distribution (QKD) and synchronized chaos which was [...] Read more.

The ability to send information securely is a vital aspect of today’s society, and with the developments in quantum computing, new ways to communicate have to be researched. We explored a novel application of quantum key distribution (QKD) and synchronized chaos which was utilized to mask a transmitted message. This communication scheme is not hampered by the ability to send single photons and consequently is not vulnerable to number splitting attacks like other QKD schemes that rely on single photon emission. This was shown by an eavesdropper gaining a maximum amount of information on the key during the first setup and listening to the key reconciliation to gain more information. We proved that there is a maximum amount of information an eavesdropper can gain during the communication, and this is insufficient to decode the message. Full article

(This article belongs to the Special Issue Cryptographic Protocols 2022)

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18 pages, 3389 KiB

Open AccessArticle

Hardware Performance Evaluation of Authenticated Encryption SAEAES with Threshold Implementation

by Takeshi Sugawara

Cryptography 2020, 4(3), 23; https://doi.org/10.3390/cryptography4030023 - 9 Aug 2020

Cited by 2 | Viewed by 4386

Abstract

SAEAES is the authenticated encryption algorithm instantiated by combining the SAEB mode of operation with AES, and a candidate of the NIST’s lightweight cryptography competition. Using AES gives the advantage of backward compatibility with the existing accelerators and coprocessors that the industry has [...] Read more.

SAEAES is the authenticated encryption algorithm instantiated by combining the SAEB mode of operation with AES, and a candidate of the NIST’s lightweight cryptography competition. Using AES gives the advantage of backward compatibility with the existing accelerators and coprocessors that the industry has invested in so far. Still, the newer lightweight block cipher (e.g., GIFT) outperforms AES in compact implementation, especially with the side-channel attack countermeasure such as threshold implementation. This paper aims to implement the first threshold implementation of SAEAES and evaluate the cost we are trading with the backward compatibility. We design a new circuit architecture using the column-oriented serialization based on the recent 3-share and uniform threshold implementation (TI) of the AES S-box based on the generalized changing of the guards. Our design uses 18,288 GE with AES’s occupation reaching 97% of the total area. Meanwhile, the circuit area is roughly three times the conventional SAEB-GIFT implementation (6229 GE) because of a large memory size needed for the AES’s non-linear key schedule and the extended states for satisfying uniformity in TI. Full article

(This article belongs to the Special Issue Side Channel and Fault Injection Attacks and Countermeasures)

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10 pages, 709 KiB

Open AccessArticle

Security Analysis of Lightweight IoT Cipher: Chaskey

by Ashutosh Dhar Dwivedi

Cryptography 2020, 4(3), 22; https://doi.org/10.3390/cryptography4030022 - 5 Aug 2020

Cited by 18 | Viewed by 4988

Abstract

This paper presents the differential cryptanalysis of ARX based cipher Chaskey using tree search based heuristic approach. ARX algorithms are suitable for resource-constrained devices such as IoT and very resistant to standard cryptanalysis such as linear or differential. To make a differential attack, [...] Read more.

This paper presents the differential cryptanalysis of ARX based cipher Chaskey using tree search based heuristic approach. ARX algorithms are suitable for resource-constrained devices such as IoT and very resistant to standard cryptanalysis such as linear or differential. To make a differential attack, it is important to make differential characteristics of the cipher. Finding differential characteristics in ARX is the most challenging task nowadays. Due to the bigger block size, it is infeasible to calculate lookup tables for non-linear components. Transition through the non-linear layer of cipher faces a huge state space problem. The problem of huge state space is a serious research topic in artificial intelligence (AI). The proposed heuristic tool use such methods inspired by Nested Tree-based sampling to find differential paths in ARX cipher and successfully applied to get a state of art results for differential cryptanalysis with a very fast and simpler framework. The algorithm can also be applied in different research areas in cryptanalysis where such huge state space is a problem. Full article

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19 pages, 398 KiB

Open AccessArticle

Implementation of a New Strongly-Asymmetric Algorithm and Its Optimization

by Koki Jimbo, Satoshi Iriyama and Massimo Regoli

Cryptography 2020, 4(3), 21; https://doi.org/10.3390/cryptography4030021 - 30 Jul 2020

Cited by 1 | Viewed by 3168

Abstract

A new public key agreement (PKA) algorithm, called the strongly-asymmetric algorithm (SAA-5), was introduced by Accardi et al. The main differences from the usual PKA algorithms are that Bob has some independent public keys and Alice produces her public key by using some [...] Read more.

A new public key agreement (PKA) algorithm, called the strongly-asymmetric algorithm (SAA-5), was introduced by Accardi et al. The main differences from the usual PKA algorithms are that Bob has some independent public keys and Alice produces her public key by using some part of the public keys from Bob. Then, the preparation and calculation processes are essentially asymmetric. This algorithms has several free parameters more than the usual symmetric PKA algorithms and the velocity of calculation is largely dependent on the parameters chosen; however, the performance of it has not yet been tested. The purpose of our study was to discuss efficient parameters to share the key with high speeds in SAA-5 and to optimize SAA-5 in terms of calculation speed. To find efficient parameters of SAA-5, we compared the calculation speed with Diffie–Hellman (D-H) while varying values of some parameters under the circumstance where the length of the secret shared key (SSK) was fixed. For optimization, we discuss a more general framework of SAA-5 to find more efficient operations. By fixing the parameters of the framework properly, a new PKA algorithm with the same security level as SAA-5 was produced. The result shows that the calculation speed of the proposed PKA algorithm is faster than D-H, especially for large key lengths. The calculation speed of the proposed PKA algorithm increases linearly as the SSK length increases, whereas D-H increases exponentially. Full article

(This article belongs to the Special Issue Cryptographic Protocols 2022)

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13 pages, 379 KiB

Open AccessArticle

Optimized CSIDH Implementation Using a 2-Torsion Point

by Donghoe Heo, Suhri Kim, Kisoon Yoon, Young-Ho Park and Seokhie Hong

Cryptography 2020, 4(3), 20; https://doi.org/10.3390/cryptography4030020 - 29 Jul 2020

Cited by 3 | Viewed by 3322

Abstract

The implementation of isogeny-based cryptography mainly use Montgomery curves, as they offer fast elliptic curve arithmetic and isogeny computation. However, although Montgomery curves have efficient 3- and 4-isogeny formula, it becomes inefficient when recovering the coefficient of the image curve for large degree [...] Read more.

The implementation of isogeny-based cryptography mainly use Montgomery curves, as they offer fast elliptic curve arithmetic and isogeny computation. However, although Montgomery curves have efficient 3- and 4-isogeny formula, it becomes inefficient when recovering the coefficient of the image curve for large degree isogenies. Because the Commutative Supersingular Isogeny Diffie-Hellman (CSIDH) requires odd-degree isogenies up to at least 587, this inefficiency is the main bottleneck of using a Montgomery curve for CSIDH. In this paper, we present a new optimization method for faster CSIDH protocols entirely on Montgomery curves. To this end, we present a new parameter for CSIDH, in which the three rational two-torsion points exist. By using the proposed parameters, the CSIDH moves around the surface. The curve coefficient of the image curve can be recovered by a two-torsion point. We also proved that the CSIDH while using the proposed parameter guarantees a free and transitive group action. Additionally, we present the implementation result using our method. We demonstrated that our method is 6.4% faster than the original CSIDH. Our works show that quite higher performance of CSIDH is achieved while only using Montgomery curves. Full article

(This article belongs to the Special Issue Post-Quantum Cryptography: From Theoretical Foundations to Practical Deployments)

24 pages, 5043 KiB

Open AccessArticle

Tamper and Clone-Resistant Authentication Scheme for Medical Image Systems

by Mayssa Tayachi, Saleh Mulhem, Wael Adi, Laurent Nana, Anca Pascu and Faouzi Benzarti

Cryptography 2020, 4(3), 19; https://doi.org/10.3390/cryptography4030019 - 6 Jul 2020

Cited by 2 | Viewed by 4448

Abstract

Telemedicine applications are more and more used due to the rapid development of digital imaging and information and communication technologies. Medical information which include digital medical images and patient’s information are extracted and transmitted over insecure networks for clinical diagnosis and treatments. Digital [...] Read more.

Telemedicine applications are more and more used due to the rapid development of digital imaging and information and communication technologies. Medical information which include digital medical images and patient’s information are extracted and transmitted over insecure networks for clinical diagnosis and treatments. Digital watermarking is one of the main approaches used to ensure the security of medical images. Nevertheless, in some cases, the only use of digital watermarking is not sufficient to reach a high level of security. Indeed, the watermark could carry essential patient information and needs to be protected. In such cases, cryptography may be used to protect the watermark and to improve the overall secured management in the medical environment. In this paper, we propose a clone-resistant watermarking approach combining a difference expansion watermarking technique with a cryptographic technique based on secret keys generated by a clone-resistant device called Secret Unknown Ciphers (SUCs). The use of SUCs to sign the watermark enforces the security of medical images during their transfer and storage. Experimental results show that the system provides a high level of security against various forms of attacks. Full article

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Cryptography, Volume 4, Issue 3 (September 2020) – 7 articles

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