Public Key Encryption for the Forgetful

In CT-RSA 2010, Yang et al. proposed a notion of public key encryption with equality test (PKEET), which allows a tester to check whether two ciphertexts encrypted under different public keys as well as the same public key contain the same message. Then various PKEET schemes are proposed to enforce authorization mechanisms for users to specify who can perform equality test on their ciphertexts. However, it is still an open problem for PKEET to resist offline message recovery attack until now. In this paper, we introduce a general two-server framework for ciphertext-checkable encryption scheme to withstand offline message recovery attack. Furthermore, it has a nice property of flexible authorization and supports checking two types of equations on the ciphertexts of \(M_{i}\) and \(M_{j}\) under different public keys as well as the same public key: \(aM_{i} = bM_{j}\) and \(M_{i}^{a} = M_{j}^{b}\), where a and b are integers.

We introduce the notion of public key encryption with secure key leasing (PKE-SKL). Our notion supports the leasing of decryption keys so that a leased key achieves the decryption functionality but comes with the guarantee that if the quantum decryption key returned by a user passes a validity test, then the user has lost the ability to decrypt. Our notion is similar in spirit to the notion of secure software leasing (SSL) introduced by Ananth and La Placa (Eurocrypt 2021) but captures significantly more general adversarial strategies. (In more detail, our adversary is not restricted to use an honest evaluation algorithm to run pirated software.) Our results can be summarized as follows: Prior to our work, the notion of single decryptor encryption (SDE) has been studied in the context of PKE (Georgiou and Zhandry, Eprint 2020) and FE (Kitigawa and Nishimaki, Asiacrypt 2022) but all their constructions rely on strong assumptions including indistinguishability obfuscation. In contrast, our constructions do not require any additional assumptions, showing that PKE/IBE/ABE/FE can be upgraded to support secure key leasing for free.

Code-based public key encryption (PKE) is a popular choice to achieve post-quantum security, partly due to its capability to achieve fast encryption/decryption. However, code-based PKE has larger ciphertext and public key sizes in comparison to conventional PKE schemes (e.g., those based on RSA). In 2018, Lau and Tan proposed a new rank metric code-based PKE scheme, which has smaller public key and ciphertext sizes compared to other code-based PKE schemes. They also proved that their scheme achieves IND-CPA security, assuming the intractability of the decisional rank syndrome decoding problem. It is known that IND-CCA2 security is the strongest and most popular security assurance for PKE schemes. Therefore, in this paper, we obtain a new code-based PKE scheme from Lau and Tan’s scheme, in order to inherit the underlying small public key and ciphertext sizes. However, our new scheme is shown to achieve IND-CCA2 security, instead of the weaker IND-CPA security. Specifically, the respective public key size and ciphertext size in our new scheme are 15.06 KB and 1.37 KB under 141-bit security level, and 16.76 KB and 1.76 KB under 154-bit security level. We then present a use case for the proposed scheme, that is for secure cloud storage.

Authenticated key agreement protocol is the fundamental building block for secure communication in the open network to ensure authentication and confidentiality of e-commerce and e-government applications. Certificateless public key cryptography combines the advantage of the identity-based public key cryptography (ID-PKC) and the traditional PKI. In this paper, we present a secure and efficient two-party authenticated key agreement protocol based on an efficient and secure certificateless public key encryption scheme. It achieves almost all the known security attributes for authenticated key agreement protocol, such as perfect forward secrecy, PKG forward secrecy, key-compromise impersonation resilience, unknown key-share resilience, message independence and no key control. Compared to other comparable schemes, it is more secure and has nice efficiency.

Public-key encryption is extensively used to provide digital data confidentiality and deliver the security features, such as nonrepudiation (digital signature) and secure key exchange. Conventional public-key schemes are based on mathematical problems with inflexible constraints, and the security of digital contents relies on computational complexity. In the era of emerging technologies, most public-key image encryption schemes are susceptible to various threats. We propose a novel public-key encryption in this article with near-ring criteria and provide confidentiality to private data with the microstates of the Einstein crystal model. The virtual oscillator generated by microstates of initial oscillators for the common secrets with the public-key scheme produces unique states to encrypt digital data. The privacy-preserved structure, that mimics the data stream of digital content with the behavior of the improved Einstein crystal model, describes a system in terms of microstates to generate diffusion in the plain data with unique states of a virtual oscillator. The performance and digital forensic evaluations, such as randomness, histogram uniformity, pixels’ correlation, pixels’ similarity, visual strength, pixels’ incongruity, key sensitivity, linear and differential attacks, noise, and occlusion attacks analyses, certify the resistivity of the proposed algorithm against potential threats and provide superior capacity in comparison to existing methodologies to hostile certain attacks.

Objective: A brand new version of RSA, known as Multi Key Generation Scheme generation scheme, has been proposed. For sensitive information, our schemes will be a useful resource in replacing the records among cloud to IoT and IoT devices. Whilst cryptography belongs to the asymmetric type, then it has public and personal keys. Methods/Statistical Analysis: For reminiscence performance, our scheme reuses the RSA scheme with a Diophantine shape of the nonlinear equation. Furthermore, our scheme overall performances well and this is especially because of the use of RSA public key. Findings: MKGS does not require multiplicative inverse function or prolonged Euclid’s algorithm. Finally, we\'ve made an experimental result on diverse stages of MKGS P.C such as key generation, encryption, and decryption via varying the N-bit modulo bits from 1K to 10K. Application/Improvements: We can develop new features rather than using Modulation bits. Keywords: Cloud computing, Cryptography, Multi Key, Public Key Cryptosystem, IoT, RSA

Selective opening (SO) security is one of the most important securities of public key encryption (PKE) in a multi-user setting. Even though messages and random coins used in some ciphertexts are leaked, SO security guarantees the confidentiality of the other ciphertexts. Actually, it is shown that there exist PKE schemes which meet the standard security such as indistinguishability against chosen ciphertext attacks (IND-CCA security) but do not meet SO security against chosen ciphertext attacks. Hence, it is important to consider SO security in the multi-user setting. On the other hand, many researchers have studied cryptosystems in the security model where adversaries can submit quantum superposition queries (i.e., quantum queries) to oracles. In particular, IND-CCA secure PKE and KEM schemes in the quantum random oracle model have been intensively studied so far.

In [1], Bellare, Boldyreva, and Micali addressed the security of public-key encryptions (PKEs) in a multi-user setting (called the BBM model in this paper). They showed that although the indistinguishability in the BBM model is induced from that in the conventional model, its reduction is far from tight in general, and this brings a serious key length problem. In this paper, we discuss PKE schemes in which the IND-CCA security in the BBM model can be obtained tightly from the IND-CCA security. We call such PKE schemes IND-CCA secure in the BBM model with invariant security reductions (briefly, SR-invariant IND-CCABBM secure). These schemes never suffer from the underlying key length problem in the BBM model. We present three instances of an SR-invariant IND-CCABBM secure PKE scheme: the first is based on the Fujisaki-Okamoto PKE scheme [7], the second is based on the Bellare-Rogaway PKE scheme [3], and the last is based on the Cramer-Shoup PKE scheme [5].

Simulation-sound trap-door commitment (SSTC) schemes are an essential ingredient for making non-malleable and universally composable protocols. In previous work, the SSTC schemes and their variants are all constructed in the same framework based on digital signatures. In this paper, we provide new constructions of SSTC schemes using encryption, which is somewhat surprising, because of the tight relationship between SSTC and digital signature schemes. Although our constructions require a few rounds of interactions between a committer and a receiver and the notion of public-key encryption could be stronger than digital signature, the resulting instantiations are much more efficient than these based on digital signature schemes. In particular, we present an efficient SSTC scheme under the CDH assumption in the bilinear groups, with a tight security reduction and short public key parameters, and the first efficient SSTC scheme under the factoring assumption. Our interactive SSTC schemes inherit properties of the non-interactive version of SSTC schemes to construct non-malleable and universally composable protocols.KeywordsSignature SchemeCommitment SchemeDigital Signature SchemeChallenge CiphertextDecryption OracleThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Currently, common image encryption methods mainly include symmetric encryption (such as AES, DES) and public key encryption (such as RSA, ECC). Although these traditional encryption methods perform well in terms of data security, they still have certain limitations in terms of multi-source data protection, efficient encryption and decryption, key management and protection against eavesdropping attacks. For example, symmetric encryption requires a secure shared secret between both sides of communication, while public key encryption is computationally complex and difficult to meet the real-time requirements of large-scale data transmission. In addition, existing encryption methods are often unable to make full use of the relevance between sources to optimize the efficiency and security of data encryption. To this end, this paper studies a source joint coding scheme based on a multi-level diversity coding system (MDCS) and applies it to image encryption. The scheme combines Shamir threshold secret sharing and source joint encryption to achieve hierarchical encryption of data by dividing images into multiple source blocks, and uses joint coding technology to improve anti-eavesdropping capabilities. On this basis, this paper further improves the shortcomings of the original source joint coding scheme, optimizes the encryption process, and enhances the security, reliability and computing efficiency of the system. Experimental results show that the scheme can improve the ability to resist attacks while ensuring the security of image encryption, providing an effective solution for image data protection in cloud computing, the Internet of Things and distributed storage environments.

SummarySecuring user identity from data breach in a web server is one of the major concerns for the users of the web applications. Similarly, protecting user access pattern from unauthorized access should be taken seriously, because the potential threats such attacks may pose, are huge. However, these security measures should not be adopted at the expense of user experience and convenience. Nevertheless, any extra overhead in the form of security measures introduced in a distributed system results in significant performance declination. The target of a secured framework for a distributed system like web application should be a reasonable trade‐off between security and user experience. Thus, in this work, we present a framework that ensures security for the user identity along with keeping the online activities of the users anonymous while ensuring scalability of the system. Our framework is designed in a scalable form that can work with other distributed architectures that provide security to user data and identities. To ensure all these measures, our proposal includes the implementation of Forward Secrecy using Diffie‐Hellman Key exchange protocol where the server cannot remember a user's history after a session ends. In addition, we present our own mechanism to hide logical data sharing strategies to protect users against selective DoS attacks. Moreover, we implemented a modified version of bloom filter to safeguard user access pattern in a compromised server. Our proposed implementation of bloom filter also ensures that the scalability of distributed system is preserved even with little infrequent overhead in the server because of security measures proposed in this work. Finally, we implemented different modules of our framework using both Web Socket and Long Polling transport protocols and recorded the time required to perform various tasks. Web socket protocol took less time to perform each task than the long polling protocol, which is convincing enough to suggest that web socket performs better than long polling in the given scenarios. Copyright © 2016 John Wiley & Sons, Ltd.

With the application of the Internet of Things (IoT) and cloud computing, the eHealthcare industry has developed markedly, attracting many patients to seek medical treatment in an eHealthcare system. However, for patients who first register in the system, due to lack of experience, an important aspect is to choose appropriate medical services. Considering the sensitivity of health care data and the semi-honest nature of the cloud server, it is a good solution to use searchable encryption (SE) to obtain some historical electronic medical records (EMRs) that are consistent with the patient's symptom keyword combination and have high service scores for reference. However, existing SE schemes still have issues meeting the requirements of the eHealthcare system for flexible authorization and revocation, efficiency, and forward privacy. To resolve these issues, we propose two efficient and privacy-preserving electronic medical records query schemes with forward privacy in a multiuser setting (EPPFM). First, we present the basic scheme EPPFM-I to achieve a multiuser multikeyword exact match query under linear search complexity. In EPPFM-I, we also use the pseudorandom function (PRF) to perform the function of forward privacy. Then, we use a bucket structure to construct the improved scheme EPPFM-II, which has a faster-than-linear search complexity. Finally, we use detailed security analysis and extensive simulations to show the security and efficiency of the proposed schemes, respectively.

In this paper, a comprehensive Quality of Security Service (QoSS) model for addressing security within a Service-Oriented Architecture (SOA) is proposed. We define a detailed SOA security model that supports and incorporates a number of networking security techniques and protocols. It utilizes symmetric keys, public keys and hash functions techniques, in order to provide different levels of QoSS agreements to satisfy the requirements of both the services providers and requesters. These levels are based on core networking security requirements such as Mutual Authentication, Session keys, Anonymity, and Perfect forward Secrecy. In addition, the proposed model forms a strong line of defense against Replay, Man-in-the-Middle, and Denial-of-Services attacks.

In public-key encryption (PKE), ciphertexts received by a receiver may be possibly correlated and the security of a PKE relies on honestly generated system parameters. Security against selective opening attacks (SOA) for PKE guarantees that even when an attacker has broken into a subset of honestly generated ciphertexts and opened them (i.e., seeing plaintexts and random bits), the unopened ciphertexts remain secure. While security against parameter subversion attacks (PSA) for PKE requires that even when the public system parameters are maliciously generated, a PKE scheme should be secure. In this paper, we initiate the study of PKE secure against both SOA and PSA. To capture SOA and PSA simultaneously, we formulate a new security notion called indistinguishability under selective opening attacks and parameter subversion attacks (IND-SO-PSA). Further, we define the lossy trapdoor function and all-but-many lossy trapdoor function in the presence of PSA (LTF-PSA and ABM-LTF-PSA correspondingly) and propose an instantiation with the efficiently-embeddable group (EG). Applying these new primitives, we construct a PKE scheme that is proven to be IND-SO-PSA secure.

Here we describe a public-key digital encryption scheme that does not require secret-key distribution — one of the Achilles’ heels of secret-key cryptographic systems because once the secret encrypting key becomes known, transmissions are no longer secret. In public-key encryption, every potential recipient of secret messages publishes his encrypting key (hence the name public key). But knowledge of the encrypting key is of no practical help in decryption. The public-key is the key to a “trap door” through which messages can vanish, not to be recovered — except through a different route to which only the legitimate receiver holds the required key, the decrypting key. (Trap door means easily in, but out only with the proper tools.) It is as if everyone had a (chained!) box in front of his house into which secret messages could be stuffed and to which only the owner had the proper opening key.KeywordsSecret MessageOriginal MessageEncrypt MessageProper ToolTrap DoorThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.