Leakage-resilient Identity-based Encryption Research Articles

A direct construction of continuous leakage-resilient (H)IBE scheme with CCA security from dual system encryption

Continuous leakage resilient semantically secure Identity-based Encryption (IBE) schemes created with dual system encryption technique were presented by Lewko et al. at TCC 2011 and Yuen et al. at Eurocrypt 2012, respectively. It has been a research challenge to achieve the security against chosen-ciphertext attacks (CCA). The previous attempts toward the CCA security rely on q-type assumptions, which are referred as non-static assumptions causing loose reduction in security proofs. In this paper, we provide a complete solution to the problem and show how to construct the continuous leakage-resilient IBE with weaker CCA security based on the dual system encryption technique, where the adversary is allowed to make continuous leakage queries. We are able to prove its security with static assumptions in the standard model. As a feature of our scheme, we allow leakage of multiple keys, i.e., leakage of the master secret key and the private key of user. Our scheme also enjoys better computational performance, since the round leakage parameter is independent of the plaintext space and has a constant size. Furthermore, our scheme can be easily extended to give the weaker CCA secure continuous leakage-resilient hierarchical identity-based encryption scheme with a short ciphertext length.

Identity-Based Encryption With Continuous Leakage-Resilient CCA Security From Static Complexity Assumption

Abstract Although a large number of provably secure cryptographic primitives have been proposed in the literature, many of these schemes might be broken in practice because of various leakage attacks. Therefore, the leakage resilience should be considered in designing these primitives. However, in identity-based cryptography, most of the existing leakage-resilient identity-based encryption (IBE) schemes suffer some limitations: they either resist the leakage attacks in the selective identity security model or achieve the chosen-ciphertext attack (CCA) security based on a non-static assumption. In this paper, an IBE scheme with adaptive leakage-resilient CCA security is proposed, and its security is rigorously proved in the random oracle model under a classic static complexity assumption, e.g. decisional bilinear Diffie–Hellman assumption. In our construction, all elements of ciphertext are randomly distributed in the adversary’s view. Hence, the adversary cannot obtain any useful information of the user’s private key from the given ciphertexts. Moreover, a unique property of our construction is that the leakage parameter is independent of the plaintext space, which contributes a better leakage rate.

A new construction of leakage-resilient CCA secure IBE scheme

Leakage of private information has become a threat to the security of cryptography systems. It has become a common security requirement that a cryptography scheme should withstand various leakage attacks. The non-interactive zero-knowledge (NIZK) argument system, one-time lossy filter (OT-LF) and one-time signature were widely used to create the generic constructions of leakage-resilient identity-based encryption (IBE) scheme with chosen-ciphertext attack (CCA) security. However, the computational efficiency of the corresponding generic construction is low because the underlying cryptographic tool is low. Thus, to solve the above problem, a new cryptographic primitive, called identity-based hash proof system with two encapsulated-key (T-IB-HPS), is proposed. The new generic constructions of leakage resilient IBE scheme with CCA security is created from the T-IB-HPS and message authentication code (MAC), and the security of the above proposed scheme is proved from the security of the underlying cryptographic tool. To further show the practicability, an instantiation of T-IB-HPS is constructed, and the formal security proof of the above instantiation is shown based on the decisional bilinear Diffie-Hellman (DBDH) assumption. Compared with the previous generic constructions of leakage resilient IBE scheme with CCA security, since the underlying cryptographic tools with low computational efficiency are not used, our generic construction has high computational efficiency.

Practical continuous leakage-resilient CCA secure identity-based encryption

Leakage of private information including private keys of user has become a threat to the security of computing systems. It has become a common security requirement that a cryptographic scheme should withstand various leakage attacks. In the real life, an adversary can break the security of cryptography primitive by performing continuous leakage attacks. Although, some research on the leakage-resilient cryptography had been made, there are still some remaining issued in previous attempts. The identity-based encryption (IBE) constructions were designed in the bounded-leakage model, and might not be able to meet their claimed security under the continuous-leakage attacks. In the real applications, the leakage is unbounded. That is, a practical cryptography scheme should keep its original security in the continuous leakage setting. The previous continuous leakage-resilient IBE schemes either only achieve chosen-plaintext attacks security or the chosen-ciphertext attacks (CCA) security is proved in the selective identity model. Aiming to solve these problems, in this paper, we show how to construct the continuous leakage-resilient IBE scheme, and the scheme’s adaptive CCA security is proved in the standard model based on the hardness of decisional bilinear Diffie-Hellman exponent assumption. For any adversary, all elements in the ciphertext are random, and an adversary cannot obtain any leakage on the private key of user from the corresponding given ciphertext. Moreover, the leakage parameter of our proposal is independent of the plaintext space and has a constant size.

Identity-based encryption with leakage-amplified chosen-ciphertext attacks security

Alwen et al. (EUROCRYPT 2010) proposed the formal definition of identity-based hash proof system (IB-HPS). As an independent interest, they showed that a leakage-resilient identity-based encryption (LR-IBE) scheme can be created based on an IB-HPS. That is, a generic construction of LR-IBE scheme with the chosen-plaintext attacks (CPA) security be designed from the IB-HPS. However, in order to further improve the practicability of identity-based encryption (IBE) system, an IBE scheme must have the chosen-ciphertext attacks (CCA) security. Hence, in this paper, a generic construction of LR-IBE scheme with the CCA security is proposed from the IB-HPS. In additional, to design an LR-IBE schemes with an arbitrarily length leakage parameter, we design a novel generic construction of leakage amplified IBE scheme with CCA security, where we only increase the size of private key proportionally, while do not change all other parameters, and the upper bound of permitted leakage can be flexibly controlled by changing the leakage-size parameter. In other words, the length of allowed leakage of our generic construction is determined by the leakage requirements of actual applications.

Identity‐based encryption resilient to continuous key leakage

Leakage of private information has become a threat to the security of computing systems. It has become a common security requirement that a cryptography scheme should withstand various leakage attacks, even the continuous leakage attacks. However, in the current constructions on the (continuous) leakage-resilient identity-based encryption (CLR-IBE) scheme, the leakage parameter is a fixed value. Aiming to solve these problems, in this study, the authors show how to construct the CLR-IBE scheme, and the adaptive chosen-ciphertext attacks security of proposed construction can be proved in the standard model. To further improve the practicability of CLR-IBE scheme, they design an improved IBE scheme with continuous leakage amplified property, and the leakage parameter has an arbitrary length.

Anonymous and Updatable Identity-Based Hash Proof System

In EUROCRYPT 2002, Alwen et al. demonstrated that an identity-based hash proof system (IB-HPS) can be used to generate an identity-based encryption (IBE) scheme, which is secure against partial leakage of the decryption key of the target identity. However, in many real-world applications, the leakage is normally unbounded, and an adversary could violate the security of such cryptography schemes by performing continuous leakage attacks. Therefore, cryptography schemes are desirable to maintain their claimed security even in the continuous leakage setting. In this paper, we first design an improved IB-HPS called updatable IB-HPS (U-IB-HPS), which has an additional key update algorithm to embed some fresh randomness into the user's private key, ensuring that enough entropy is maintained in the updated keys. Then, we further use the U-IB-HPS to propose a generic construction of continuously leakage-resilient IBE schemes. Finally, an instantiation of the U-IB-HPS with anonymity is presented. As a result, our construction delivers an anonymous IBE scheme that is secure against continuous leakage of user's private key. The security of our proposed scheme has been proved in the random oracle model under the classic decisional bilinear Diffie–Hellman assumption, which is a standard static security assumption.

Continuous Leakage-Resilient Identity-Based Encryption Scheme with CCA Security

Leakage of private information including private key has become a threat to the security of computing systems. It has become a common security requirement that a cryptographic scheme should withstand various leakage attacks, including continuous leakage attacks. In order to obtain an Identity-based encryption (IBE) scheme which can keep its original security in the continuous leakage setting, we propose a new construction method of IBE scheme with Chosen-ciphertext attacks (CCA) security, which can tolerate continuous leakage attacks on many private keys of each identity, and whose security is proved based on the hardness of the classical Decisional bilinear Diffie-Hellman (DBDH) assumption in the standard model. The leakage parameter is independent of the plaintext space and has the constant size.

Continuous leakage-resilient identity-based encryption with leakage amplification

In modern computer systems, leakage of private information may cause catastrophic consequences, especially those are related to the secret keys in cryptographic mechanisms. Therefore, it has been widely accepted both in academia and industry that cryptographic schemes should withstand various leakage attacks, including the continuous leakage attacks. Although a lot of researches have been conducted towards this issue and some progresses have been made, there are still many unsolved problems in this area. For example, in the majority of the existing identity-based encryption (IBE) schemes with (continuous) leakage resilience, the upper bound of leakage is required to be fixed. But in many real-world applications, such a requirement is inadequate to protect the schemes against the leakage attacks. Moreover, many previous efforts aiming to build IBE schemes that are secure against the chosen-ciphertext attacks (CCA) need to rely on the q-type assumptions. But these solutions are not desirable, because the q-type assumptions are non-static assumptions. In this paper, in order to address the above mentioned problems, we demonstrate how to construct a continuous leakage-resilient CCA-secure IBE scheme with leakage amplification, in which the leakage parameter has an arbitrary length. The benefit is that the length of permitted leakage in our scheme can be adjusted flexibly according to the leakage requirements. Moreover, the security of our proposed scheme can be proved with static assumptions in the standard model. Compared with the related works in the literature, our scheme enjoys a unique feature that it allows continuous leakage of multiple keys simultaneously, e.g. continuous leakage of the master secret key as well as the user’s private key.

Continuous Leakage-Resilient Identity-Based Encryption with Tight Security

Abstract In the actual applications, an adversary can break the security of cryptography scheme through various leakage attacks (e.g. side-channel attacks, cold-boot attacks, etc.), even the continuous leakage attacks. That is, a practical cryptography scheme must maintain its claimed security in the continuous leakage setting. However, the previous constructions on the leakage-resilient identity-based encryption (IBE) scheme could tolerate a leakage that is bounded, and cannot resist the continuous leakage attacks. In order to further achieve the better security, a novel method to build the continuous leakage-resilient IBE scheme with tight security is presented in this paper, and the scheme’s security is proved, in the standard model, based on a stronger security assumption that depends on the number of queries made by the adversary. In addition, our proposal has several advantages over previous such constructions, e.g. shorter public parameters, higher communication efficiency, tight security, etc.

The generic construction of continuous leakage-resilient identity-based cryptosystems

In the leakage setting, the adversary is allowed to access the internal secret states of a cryptosystem, such as the private key of user and the master secret key. In the continuous leakage model, there is no predetermined bound on the leakage of internal secret states; therefore, it is more challenging. In this paper, we present a new primitive called updatable identity-based hash proof system (U-IB-HPS), which can serve as a fundamental tool for constructing continuous leakage-resilient identity-based cryptosystems. With the U-IB-HPS, we obtain the generic constructions of identity-based cryptosystem with continuous leakage-resilience, such as the continuous leakage-resilient identity-based encryption with leakage amplification, the continuous leakage-resilient identity-based hybrid encryption with leakage amplification, etc. As a feature of our generic constructions, we allow the leakage of multiple keys, i.e., leakage of the master secret key and the private key of user. In addition, we present a generic framework of one-round identity-based authenticated key exchange (AKE) protocol with continuous leakage resilience, which ensures the session key security even if the adversary performs continuous leakage attacks during the execution of a session. We also present instantiations of U-IB-HPS from bilinear groups and composite order bilinear groups, respectively. The security of our instantiations is based on the standard static assumptions, such as the decisional bilinear Diffie–Hellman assumption, the corresponding complexity assumptions over composite order bilinear groups, etc. Our instantiations can be easily extended to construct the updatable hierarchical identity-based hash proof system.

Continuous Leakage-Resilient Identity-Based Encryption without Random Oracles

Provably secure identity-based encryption (IBE) schemes in the presence of key-leakage have attracted a lot of attention recently. However, most of them were designed in the bounded-leakage model, and might not be able to meet the claimed security under the continuous-leakage attacks. The main issue is that the most of previous leakage-resilient IBE schemes could not ensure the randomness of all elements in the ciphertext, because some elements can be written as a function on the private key of user; therefore, the adversary can obtain the leakage on the private key of user from the corresponding given ciphertext. In this paper, a new construction of CCA-secure IBE scheme tolerating continuous-leakage attacks in the standard model is proposed, and its security is proved in the selective-ID security model based on the hardness of decisional bilinear Diffie–Hellman assumption, which is a classical static assumption. In our construction, the adversary cannot obtain any leakage on the private key from the corresponding ciphertext, since all elements in the ciphertext are random in the adversary’s view. The striking advantage of our constructions is the key leakage ratio, which is the best one among the previous leakage-resilient IBE constructions.

A Leakage-Resilient CCA-Secure Identity-Based Encryption Scheme

Identity-based encryption (IBE) has many appealing applications. However, some traditional IBE schemes may not be secure in the real world due to the side-channel attacks. Leakage-resilient cryptography can capture these attacks by modeling information leakage that adversary can access. In this paper, we apply a hash proof technique in the existing CCA-secure variant of the Gentry's IBE scheme to construct a new leakage-resilient IBE scheme in the bounded-leakage model. The proposed scheme is more computationally efficient than the original Alwen et al. 's leakage-resilient IBE scheme. It enjoys a shorter key (public/secret key) length, and a higher relative key leakage ratio. The new leakage-resilient scheme is proved semantically secure against adaptive chosen ciphertext attack in the standard model under the truncated augmented bilinear Diffie-Hellman exponent ( |$q$| -TABDHE) assumption.

Leakage-resilient identity-based encryption scheme

We propose a leakage-resilient Identity-Based Encryption IBE scheme in the relative leakage mode. The semantic security of the proposed scheme is proved in two ways in the random oracle model under the Decisional Square Bilinear Diffie-Hellman D-Square-BDH assumption. Compared with some existing leakage-resilient IBE schemes, our construction enjoys a shorter parameter length, a lower computation cost and a higher ratio of the key leakage for the same level of security.