A HYBRIDIZED ENCRYPTION SCHEME BASED ON ELLIPTIC CURVE CRYPTOGRAPHY FOR SECURING DATA IN SMART HEALTHCARE

Recent developments in smart healthcare have brought us a great deal of convenience. Connecting common objects to the Internet is made possible by the Internet of Things (IoT). These connected gadgets have sensors and actuators for data collection and transfer. However, if users' private health information is compromised or exposed, it will seriously harm their privacy and may endanger their lives. In order to encrypt data and establish perfectly alright access control for such sensitive information, attribute-based encryption (ABE) has typically been used. Traditional ABE, however, has a high processing overhead. As a result, an effective security system algorithm based on ABE and Fully Homomorphic Encryption (FHE) is developed to protect health-related data. ABE is a workable option for one-to-many communication and perfectly alright access management of encrypting data in a cloud environment. Without needing to decode the encrypted data, cloud servers can use the FHE algorithm to take valid actions on it. Because of its potential to provide excellent security with a tiny key size, elliptic curve cryptography (ECC) algorithm is also used. As a result, when compared to related existing methods in the literature, the suggested hybridized algorithm (ABE-FHE-ECC) has reduced computation and storage overheads. A comprehensive safety evidence clearly shows that the suggested method is protected by the Decisional Bilinear Diffie-Hellman postulate. The experimental results demonstrate that this system is more effective for devices with limited resources than the conventional ABE when the system’s performance is assessed by utilizing standard model

Survey on securing data storage in the cloud

Cloud Computing has become a well-known primitive nowadays; many researchers and companies are embracing this fascinating technology with feverish haste. In the meantime, security and privacy challenges are brought forward while the number of cloud storage user increases expeditiously. In this work, we conduct an in-depth survey on recent research activities of cloud storage security in association with cloud computing. After an overview of the cloud storage system and its security problem, we focus on the key security requirement triad, i.e., data integrity, data confidentiality, and availability. For each of the three security objectives, we discuss the new unique challenges faced by the cloud storage services, summarize key issues discussed in the current literature, examine, and compare the existing and emerging approaches proposed to meet those new challenges, and point out possible extensions and futuristic research opportunities. The goal of our paper is to provide a state-of-the-art knowledge to new researchers who would like to join this exciting new field

Efficient secret key reusing attribute-based encryption from lattices

Attribute-based encryption (ABE) schemes by lattices are likely to resist quantum attacks, and can be widely applied to many Internet of Thing or cloud scenarios. One of the most attractive feature for ABE is the ability of fine-grained access control which provides an effective way to ensure data security. In this work, we propose an efficient ciphertext policy attribute-based encryption scheme based on hardness assumption of LWE. Being different from other similar schemes, a user\u27s secret key can only be generated once only and it can be used to decrypt ciphertext under different access policies by making combinations of secret key fragments. Specially, we propose a method for binding users\u27 secret keys with their attributes and identities, which solves the collusion attack problem. The security of the scheme is proved to be selective secure under the LWE assumption

Reducing the computational complexity of fuzzy identity-based encryption from lattice

In order to provide access control on encrypted data, Attribute-based encryption (ABE) defines each user using a set of attributes. Fuzzy identity-based encryption (FIBE) is a variant of ABE that allows for a threshold access structure for users. To address the potential threat posed by future quantum computers, this paper presents a post-quantum fuzzy IBE scheme based on lattices. However, current lattice-based ABE schemes face challenges related to computational complexity and the length of ciphertext and keys. This paper aims to improve the performance of an existing fuzzy IBE scheme by reducing key length and computational complexity during the encryption phase. While negative attributes are not utilized in our scheme, we prove its security under the learning with error (LWE) hard problem assumption in the selective security model. These improvements have significant implications for the field of ABE

Improved (Hierarchical) Inner-Product Encryption from Lattices

Inner-product encryption (IPE) provides fine-grained access control and has attractive applications. Agrawal, Freeman, and Vaikuntanathan~(Asiacrypt 2011) proposed the first IPE scheme from lattices by twisting the identity-based encryption (IBE) scheme by Agrawal, Boneh, and Boyen~(Eurocrypt 2010). Their IPE scheme supports inner-product predicates over $R^{\mu}$, where the ring is $R = \mathbb{Z}_q$. Several applications require the ring $R$ to be exponentially large and, thus, they set $q = 2^{O(n)}$ to implement such applications. This choice results in the AFV IPE scheme with public parameters of size $O(\mu n^2 \lg^3{q}) = O(\mu n^5)$ and ciphertexts of size $O(\mu n \lg^3{q}) = O(\mu n^4)$, where $n$ is the security parameter. Hence, this makes the scheme impractical, as they noted. We address this efficiency issue by ``untwisting\u27\u27 their twist and providing another twist. Our scheme supports inner-product predicates over $R^\mu$ where $R = \mathrm{GF}(q^n)$ instead of $\mathbb{Z}_q$. Our scheme has public parameters of size $O(\mu n^2 \lg^2{q})$ and ciphertexts of size $O(\mu n \lg^2{q})$. Since the cardinality of $\mathrm{GF}(q^n)$ is inherently exponential in $n$, we have no need to set $q$ as the exponential size for applications. As side contributions, we extend our IPE scheme to a hierarchical IPE (HIPE) scheme and propose a fuzzy IBE scheme from IPE. Our HIPE scheme is more efficient than that developed by Abdalla, De Caro, and Mochetti (Latincrypt 2012). Our fuzzy IBE is secure under a much weaker assumption than that employed by Agrawal et al.~(PKC 2012), who constructed the first lattice-based fuzzy IBE scheme

Contributions to Lattice–based Cryptography

Post–quantum cryptography (PQC) is a new and fast–growing part of Cryptography. It focuses on developing cryptographic algorithms and protocols that resist quantum adversaries (i.e., the adversaries who have access to quantum computers). To construct a new PQC primitive, a designer must use a mathematical problem intractable for the quantum adversary. Many intractability assumptions are being used in PQC. There seems to be a consensus in the research community that the most promising are intractable/hard problems in lattices. However, lattice–based cryptography still needs more research to make it more efficient and practical. The thesis contributes toward achieving either the novelty or the practicality of lattice– based cryptographic systems

Revocable Hierarchical Attribute-based Signatures from Lattices

Attribute-based Signatures (ABS) allow users to obtain attributes from issuing authorities, and sign messages whilst simultaneously proving compliance of their attributes with a verification policy. ABS demands that both the signer and the set of attributes used to satisfy a policy remain hidden to the verifier. Hierarchical ABS (HABS) supporting roots of trust and delegation were recently proposed to alleviate scalability issues in centralised ABS schemes. An important yet challenging property for privacy-preserving ABS is revocation, which may be applied to signers or some of the attributes they possess. Existing ABS schemes lack efficient revocation of either signers or their attributes, relying on generic costly proofs.Moreover, in HABS there is a further need to support revocation of authorities on the delegation paths, which is not provided by existing HABS constructions. This paper proposes a direct HABS scheme with a Verifier-Local Revocation (VLR) property. We extend the original HABS security model to address revocation and develop a new attribute delegation technique with appropriate VLR mechanism for HABS, which also implies the first ABS scheme to support VLR. Moreover, our scheme supports inner-product signing policies, offering a wider class of attribute relations than previous HABS schemes, and is the first to be based on lattices, which are thought to offer post-quantum security

Encriptação com predicados baseada em reticulados

Orientadores: Ricardo Dahab, Michel AbdallaTese (doutorado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: Em um sistema de criptografia funcional, uma autoridade de posse de uma chave mestra pode gerar uma chave secreta que permite o cálculo de uma função sobre a mensagem nos dados criptografados. Assim, é possível calcular tal função no texto cifrado usando somente a chave secreta. Exemplos importantes de criptografia funcional são Criptografia Baseada em Identidades, Criptografia Baseada em Atributos, Criptografia com Produto Escalar, Criptografia Difusa Baseada em Identidades, Criptografia de Vector Oculto, Criptografia Baseada em Certificados, Criptografia com Pesquisa de Palavra-Chave e Criptografia Baseada em Identidades com Curinga. Esquemas de criptografia com predicados são uma especialização de esquemas de criptografia funcionais, em que a função utilizada não fornece informações sobre a mensagem, mas determina se a decriptação deve ou não funcionar corretamente. Criptografia baseada em reticulados é uma importante alternativa para os principais sistemas criptográficos utilizados atualmente, uma vez que elas são supostamente seguras contra algoritmos quânticos. O Algoritmo de Shor é capaz de resolver o Problema da Fatoração Inteira e o Problema do Logaritmo Discreto em tempo polinomial em um computador quântico, quebrando os sistemas criptográficos mais usados e importantes atualmente, como o RSA, o Diffie-Hellman e a Criptografia de Curvas Elípticas. Neste trabalho nos concentramos em esquemas de criptografia com predicados baseados em reticulados. Nós estudamos e descrevemos os principais sistemas baseados em reticulados encontrados na literatura, estendendo-os a versões hierárquicas e mostrando como o uso de um reticulado com estrutura ideal afeta a prova de segurança. Para cada esquema, uma prova formal de segurança é detalhada, as análises de complexidade e do tamanho das variáveis são mostradas e a escolha dos parâmetros garantindo o funcionamento correto da decriptação é dadaAbstract: In a functional encryption system, an authority holding a master secret key can generate a key that enables the computation of some function on the encrypted data. Then, using the secret key the decryptor can compute the function from the ciphertext. Important examples of functional encryption are Identity-Based Encryption, Attribute-Based Encryption, Inner Product Encryption, Fuzzy Identity-Based Encryption, Hidden Vector Encryption, Certificate-Based Encryption, Public Key Encryption with Keyword Search and Identity-Based Encryption with Wildcards. Predicate encryption schemes are a specialization of functional encryption schemes, in which the function does not give information of the plaintext, but it determines whether the decryption should or should not work properly. Lattice-Based Cryptography is an important alternative to the main cryptographic systems used today, since they are conjectured to be secure against quantum algorithms. Shor's algorithm is capable of solving the Integer Factorization Problem and the Discrete Logarithm Problem in polynomial time on a quantum computer, breaking the most used and important cryptosystems such as RSA, Diffie-Hellman and Elliptic Curve Cryptography. In this work we focus on Lattice-Based Predicate Encryption. We study and describe the main lattice-based schemes found in the literature, extending them to hierarchical versions and showing how the use of ideal lattice affects their security proof. For each scheme, a formal proof of security is detailed, analyses of complexity and variable's size are shown and the parameter's choice ensuring that the decryption works correctly is givenDoutoradoCiência da ComputaçãoDoutora em Ciência da Computaçã

Fully Secure Attribute-Based Encryption for tt-CNF from LWE

Attribute-based Encryption (ABE), first introduced by [SW05,GPSW06], is a public key encryption system that can support multiple users with varying decryption permissions. One of the main properties of such schemes is the supported function class of policies. While there are fully secure constructions from bilinear maps for a fairly large class of policies, the situation with lattice-based constructions is less satisfactory and many efforts were made to close this gap. Prior to this work the only known fully secure lattice construction was for the class of point functions (also known as IBE). In this work we construct for the first time a lattice-based (ciphertext-policy) ABE scheme for the function class $t$-CNF, which consists of CNF formulas where each clause depends on at most $t$ bits of the input, for any constant $t$. This class includes NP-verification policies, bit-fixing policies and $t$-threshold policies. Towards this goal we also construct a fully secure single-key constrained PRF from OWF for the same function class, which might be of independent interest

Research Philosophy of Modern Cryptography

Proposing novel cryptography schemes (e.g., encryption, signatures, and protocols) is one of the main research goals in modern cryptography. In this paper, based on more than 800 research papers since 1976 that we have surveyed, we introduce the research philosophy of cryptography behind these papers. We use ``benefits and ``novelty as the keywords to introduce the research philosophy of proposing new schemes, assuming that there is already one scheme proposed for a cryptography notion. Next, we introduce how benefits were explored in the literature and we have categorized the methodology into 3 ways for benefits, 6 types of benefits, and 17 benefit areas. As examples, we introduce 40 research strategies within these benefit areas that were invented in the literature. The introduced research strategies have covered most cryptography schemes published in top-tier cryptography conferences