Deterministic Public-key Encryption Research Articles

CCA-security from adaptive all-but-one lossy trapdoor functions

In this paper, we propose the notion of adaptive all-but-one lossy trapdoor functions (aABO-LTFs), a variant of all-but-one lossy trapdoor functions. An aABO-LTF is parameterised by a set of branches. Given the lossy branch, the function statistically loses the information of its inputs. Given injective branches, the function is injective, and there is a trapdoor that enables efficient function inversion. What differentiates an aABO-LTF and an ABO-LTF is that for an aABO-LTF, the lossy branch is indistinguishable from the other branches even if the adversary gets to ask for function inversions on any injective branches apart from the lossy branch.We demonstrate the usefulness of the adaptivity of aABO-LTFs by providing generic and efficient constructions of an adaptively chosen-ciphertext secure (CCA-secure) public-key encapsulation mechanism (KEM) and an adaptive deterministic public-key encryption (DPKE) without random oracles using aABO-LTFs in a very simple black-box way. Our constructions are direct in the sense of that it avoids generic transformations using one-time signatures or message authentication codes typically found in standard model CCA-secure constructions.Moreover, we show that aABO-LTFs can be instantiated generically by lossy trapdoor primitives, including lossy trapdoor functions (LTFs) and identity-based (lossy) trapdoor functions (IB-LTFs). We also demonstrate that the lattice-based ABO-LTFs proposed by Alwen et al. (CRYPTO'13) are aABO-LTFs. Several existing CCA-secure KEM and DPKE schemes can be described by our generic constrictions. Therefore, our work unifies these seemingly unrelated schemes and explains the design principles behind these schemes.

Blockchain-based Fair and Decentralized Data Trading Model

Abstract Data is a kind of important asset in the digital economy and is driving the rise of data markets. Meanwhile, data markets promote data trading efficiently and improve the utilization of data. However, several challenges about data trading need to be addressed. Here, we resolve these challenges via our blockchain-based fair and decentralized data trading model. Disputes about data correctness is settled by the decentralized arbitration mechanism in our model. To ensure the fairness of data trading, we integrate a sale contract and a deterministic public-key encryption algorithm. The decentralization feature of blockchain cuts off the single-point failure for the data trading platform. In addition, we prove that the proposed protocol achieves the desirable security properties that a secure data trading protocol should have. Moreover, utilizing the smart contract in Solidity and program in Java, we implement our model and then evaluate its performance.

Multi-use Deterministic Public Key Proxy Re-Encryption from Lattices in the Auxiliary-Input Setting

Proxy Re-Encryption (PRE) is a cryptographic primitive that allows a proxy to turn an Alice’s ciphertext into a Bob’s ciphertext on the same plaintext. All of the PRE schemes are public key encryption and semantic security. Deterministic Public Key Encryption (D-PKE) provides an alternative to randomized public key encryption in various scenarios where the latter exhibits inherent drawbacks. In this paper, we construct the first multi-use unidirectional D-PRE scheme from Lattices in the auxiliary-input setting. We also prove that it is PRIV1-INDr secure in the standard model based on the LWR. Finally, an identity-based D-PRE is obtained from the basic construction.

Updatable Lossy Trapdoor Functions Under Consecutive Leakage

Abstract Lossy trapdoor functions (LTFs), introduced by Peikert and Waters (STOC’08), have already been found to be a very useful tool in constructing complex cryptographic primitives in a black-box manner, such as one-way trapdoor functions, deterministic public-key encryption, CCA-secure public-key encryption, etc. Due to the existence of the side-channel attack, the leakage of trapdoor information in lossy trapdoor function systems can lead to the impossibility of provable security. Recently, Zhang et al. introduced a model of consecutive and continual leakage-resilient and updatable lossy trapdoor functions (ULTFs) and provided a concrete construction to achieve the security. Meanwhile, they proposed a consecutive and continual leakage-resilient public-key encryption scheme. However, in this paper, we demonstrate that the correctness of injective function can not be satisfied. Furthermore, the attacker can easily distinguish the evaluation key of ULTFs generated by the challenger according to the security model. Finally, we show two new constructions based on the continual leakage-resilient public-key encryption scheme of Brakerski et al. (FOCS 2010) and demonstrate the security of our scheme in the consecutive and continual leakage model.

A generic construction of CCA-secure deterministic encryption

Deterministic public-key encryption (D-PKE), introduced by Bellare, Boldyreva, and O'Neill (CRYPTO'07), encrypts every plaintext into a unique ciphertext without using any randomness. Compared with the traditional randomized public-key encryptions, D-PKE has advantages in searching encrypted values across the database thanks to its lower computational overheads. In the literature, Bellare et al. gave the “strongest possible” notion of security for this primitive, called PRIV, and they also showed how this notion can be achieved in the random oracle model. Afterwards, Boldyreva, Fehr, and O'Neill (CRYPTO'08), followed by many other researchers, designed chosen ciphertext attack (CCA) secure D-PKE schemes in the standard model. These works are all based on lossy trapdoor functions and all-but-one trapdoor functions. In this paper, we present an alternative paradigm to design CCA-secure D-PKE. Our approach is a generic construction based on the identity-based lossy trapdoor functions (IB-LTDF), and it also can be extended to design CCA secure deterministic identity-based encryption schemes (D-IBE). To the best of our knowledge, this gives the first efficient construction of CCA-secure D-IBE schemes. Moreover, our approach can be considered as another application of the CHK transformation.

CCA-Secure Deterministic Identity-Based Encryption Scheme

Deterministic public-key encryption, encrypting a plaintext into a unique ciphertext without involving any randomness, was introduced by Bellare, Boldyreva, and O'Neill (CRYPTO 2007) as a realistic alternative to some inherent drawbacks in randomized public-key encryption. Bellare, Kiltz, Peikert and Waters (EUROCRYPT 2012) bring deterministic public-key encryption to the identity-based setting, and propose deterministic identity-based encryption scheme (DIBE). Although the construc- tions of chosen plaintext attack (CPA) secure DIBE scheme have been studied intensively, the construction of chosen ciphertext attack (CCA) secure DIBE scheme is still challenging problems. In this paper, we introduce the notion of identity-based all-but-one trapdoor functions (IB-ABO-TDF), which is an extension version of all-but-one lossy trapdoor function in the public-key setting. We give a instantiation of IB-ABO-TDF under decisional linear assumption. Based on an identity-based lossy trapdoor function and our IB-ABO-TDF, we present a generic construction of CCA-secure DIBE scheme.

Deterministic Public-Key Encryption for Adaptively-Chosen Plaintext Distributions

Bellare, Boldyreva, and O’Neill (CRYPTO ’07) initiated the study of deterministic public-key encryption as an alternative in scenarios where randomized encryption has inherent drawbacks. The resulting line of research has so far guaranteed security only for adversarially-chosen plaintext distributions that are independent of the public key used by the scheme. In most scenarios, however, it is typically not realistic to assume that adversaries do not take the public key into account when attacking a scheme.

Incremental Deterministic Public-Key Encryption

Motivated by applications in large storage systems, we initiate the study of incremental deterministic public-key encryption. Deterministic public-key encryption, introduced by Bellare, Boldyreva, and O'Neill (CRYPTO '07), provides an alternative to randomized public-key encryption in various scenarios where the latter exhibits inherent drawbacks. A deterministic encryption algorithm, however, cannot satisfy any meaningful notion of security for low-entropy plaintexts distributions, but Bellare et al. demonstrated that a strong notion of security can in fact be realized for relatively high-entropy plaintext distributions. In order to achieve a meaningful level of security, a deterministic encryption algorithm should be typically used for encrypting rather long plaintexts for ensuring a sufficient amount of entropy. This requirement may be at odds with efficiency constraints, such as communication complexity and computation complexity in the presence of small updates. Thus, a highly desirable property of deterministic encryption algorithms is incrementality: Small changes in the plaintext translate into small changes in the corresponding ciphertext. We present a framework for modeling the incrementality of deterministic public-key encryption. Our framework extends the study of the incrementality of cryptography primitives initiated by Bellare, Goldreich and Goldwasser (CRYPTO '94). Within our framework, we propose two schemes, which we prove to enjoy an optimal tradeoff between their security and incrementality up to lower-order factors. Our first scheme is a generic method which can be based on any deterministic public-key encryption scheme, and, in particular, can be instantiated with any semantically secure (randomized) public-key encryption scheme in the random-oracle model. Our second scheme is based on the Decisional Diffie---Hellman assumption in the standard model. The approach underpinning our schemes is inspired by the fundamental "sample-then-extract" technique due to Nisan and Zuckerman (JCSS '96) and refined by Vadhan (J. Cryptology '04), and by the closely related notion of "locally computable extractors" due to Vadhan. Most notably, whereas Vadhan used such extractors to construct private-key encryption schemes in the bounded-storage model, we show that techniques along these lines can also be used to construct incremental public-key encryption schemes.

A Unified Approach to Deterministic Encryption: New Constructions and a Connection to Computational Entropy

This paper addresses deterministic public-key encryption schemes (DE), which are designed to provide meaningful security when only source of randomness in the encryption process comes from the message itself. We propose a general construction of DE that unifies prior work and gives novel schemes. Specifically, its instantiations include: The security proofs for these schemes are enabled by three tools that are of broader interest: We also extend our result about computational entropy to the average case, which is useful in reasoning about leakage-resilient cryptography: leaking λ bits of information reduces the quality of computational entropy by a factor of 2 λ and its quantity by λ.

Better Security for Deterministic Public-Key Encryption: The Auxiliary-Input Setting

Deterministic public-key encryption, introduced by Bellare, Boldyreva, and O’Neill (CRYPTO ’07), provides an alternative to randomized public-key encryption in various scenarios where the latter exhibits inherent drawbacks. A deterministic encryption algorithm, however, cannot satisfy any meaningful notion of security when the plaintext is distributed over a small set. Bellare et al. addressed this difficulty by requiring semantic security to hold only when the plaintext has high min-entropy from the adversary’s point of view.In many applications, however, an adversary may obtain auxiliary information that is related to the plaintext. Specifically, when deterministic encryption is used as a building block of a larger system, it is rather likely that plaintexts do not have high min-entropy from the adversary’s point of view. In such cases, the framework of Bellare et al. might fall short from providing robust security guarantees.We formalize a framework for studying the security of deterministic public-key encryption schemes with respect to auxiliary inputs. Given the trivial requirement that the plaintext should not be efficiently recoverable from the auxiliary input, we focus on hard-to-invert auxiliary inputs. Within this framework, we propose two schemes: the first is based on the d-linear assumption for any d≥1 (including, in particular, the decisional Diffie–Hellman assumption), and the second is based on a rather general class of subgroup indistinguishability assumptions (including, in particular, the quadratic residuosity assumption and Paillier’s composite residuosity assumption). Our schemes are secure with respect to any auxiliary input that is subexponentially hard to invert (assuming the standard hardness of the underlying computational assumptions).In addition, our first scheme is secure even in the multi-user setting where related plaintexts may be encrypted under multiple public keys. Constructing a scheme that is secure in the multi-user setting (even without considering auxiliary inputs) was identified by Bellare et al. as an important open problem.

An Efficient Software Anti-Piracy Scheme

Software piracy is the major challenge to software providers, and most trade organizations today face problems with software piracy. As a result, there are several developed systems available in the market to deal with this problem. Unfortunately, the majority of these systems do not provide an appropriate solution and the problem has not been solved yet. After reviewing the nature of existing systems, the author found that these systems do not take in their consideration the international standard specifications to treat this problem. Therefore, it is difficult for these systems to prevent or stop piracy. Thus the purpose of this paper is to develop a new scheme carrying the characteristics of international standard specifications in order to be able to prevent piracy in any country by utilizing the Internet and Web services, by using one from the deterministic public key encryption scheme, namely ElGamal scheme, and by using zero knowledge proof of identity technique to grant the users access to a scheme correctly and also to use the international standard copy number, to ease many of these difficulties. Results are given from which the conclusion drawn is that developing a new scheme entitled “An Efficient Software Anti-Piracy Scheme” can help significantly in the work of trade organizations and software providers suffering from software piracy. Some recent patents are also discussed in this paper. Keywords: Static protection, dynamic protection, software piracy attacks, identification, authentication