Multi-authority attribute-based encryption (MA-ABE) has received increasing attention due to the proliferation of decentralized applications and services. Since its inception, various constructions have been proposed with different security assumptions. However, in light of the threat from quantum attacks, one major challenge is to construct an MA-ABE with post-quantum cryptography techniques. Nonetheless, existing post-quantum solutions have so far been constrained by either efficiency or the need for interactions among authorities, which limits the application of MA-ABE in emerging decentralized applications. In this work, we propose a truly decentralized and more efficient MA-ABE by leveraging the Ring Learning with Error (RLWE) problem. We achieve this by first adapting the generalized compact knapsack problem for an efficient lattice trapdoor sampler. To support any DNF access policy, we develop a ring-based monotone linear secret sharing scheme derived from the Lewko-Waters transformation. The complexity analysis shows that compared to the state of the art, our scheme improves by a factor of N2/logN on encryption and N/logN on decryption, where N is the lattice dimension. Experimental results demonstrate an encryption and decryption time of 28.60 and 15.71 seconds respectively when N =1024, thereby showing the feasibility of our construction in real-world applications.
Multi-authority attribute-based encryption (MA-ABE) has received increasing attention due to the proliferation of decentralized applications and services. Since its inception, various constructions have been proposed with different security assumptions. However, in light of the threat from quantum attacks, one major challenge is to construct an MA-ABE with post-quantum cryptography techniques. Nonetheless, existing post-quantum solutions have so far been constrained by either efficiency or the need for interactions among authorities, which limits the application of MA-ABE in emerging decentralized applications. In this work, we propose a truly decentralized and more efficient MA-ABE by leveraging the Ring Learning with Error (RLWE) problem. We achieve this by first adapting the generalized compact knapsack problem for an efficient lattice trapdoor sampler. To support any DNF access policy, we develop a ring-based monotone linear secret sharing scheme derived from the Lewko-Waters transformation. The complexity analysis shows that compared to the state of the art, our scheme improves by a factor of N2/logN on encryption and N/logN on decryption, where N is the lattice dimension. Experimental results demonstrate an encryption and decryption time of 28.60 and 15.71 seconds respectively when N =1024, thereby showing the feasibility of our construction in real-world applications.
This article deals with designing an efficient post-quantum lattice based encryption scheme that relies on the multi-authority Ciphertext-Policy Attribute-Based Encryption (CP-ABE). The security of the proposed scheme is based on the hardness of the ring learning with errors (RLWE) problem. The construction of the proposed scheme is done using the Shamir's threshold secret sharing along with the Lagrange interpolation during the key generation and decryption processes in order to achieve the segmentation and restoration of private keys. A comparative study with the existing state of art schemes has been performed to show the feasibility and efficiency of the proposed scheme. Furthermore, experiments on the proposed scheme have been conducted to illustrate the computational time required during the key generation, encryption and decryption processes.
Ciphertext policy attribute-based encryption (CP-ABE) is a promising cryptographic technology that provides fine-grained access control as well as data confidentiality. It enables one sender to encrypt the data for more receivers, and to specify a policy on who can decrypt the ciphertext using his/her attributes alone. However, most existing ABE schemes are constructed on bilinear maps and they cannot resist quantum attacks. In this paper, we propose a multi-authority CP-ABE (MA-CPABE) scheme on ideal lattices which is still secure in post-quantum era. On one hand, multiple attribute authorities are required when user's attributes cannot be managed by a central authority. On the other hand, compared with generic lattice, the ideal lattice has extra algebraic structure and can be used to construct more efficient cryptographic applications. By adding some virtual attributes for each authority, our scheme can support flexible threshold access policy. Security analysis shows that the proposed scheme is secure against chosen plaintext attack (CPA) in the standard model under the ring learning with errors (R-LWE) assumption.
The advent of quantum computing poses a significant threat to traditional cryptographic algorithms, including RSA, Diffie-Hellman, and Elliptic Curve Cryptography, due to the capabilities of quantum algorithms like Shor’s algorithm. Post-quantum cryptography (PQC) has emerged to address these challenges, with lattice-based cryptography (LBC) being a prominent candidate. LBC, underpinned by hard mathematical problems like Learning with Errors (LWE) and Ring-LWE (RLWE), offers robust security against quantum and classical adversaries. In parallel, Ciphertext-Policy Attribute-Based Encryption (CPABE) has become a critical tool for enabling fine-grained access control in data-sharing scenarios, such as secure cloud storage and IoT. While existing CP-ABE implementations rely on bilinear pairings vulnerable to quantum attacks, lattice-based CPABE schemes provide a quantum-resistant alternative. Despite their potential, these schemes face challenges in computational efficiency, collusion resistance, and implementation correctness. Our contributions include a detailed mathematical breakdown of one of the state-of-the-art (SOTA) lattice-based CP-ABE schemes and a novel correctness proof for the same scheme.
The recent promising results on the hardness of lattice problems have inspired the construction of several Attribute-based Encryption (ABE) schemes from the quantum resistant perspective. However, these schemes are insufficient enough for supporting real-world applications due to inherent quadratic overhead problem in the use of Learning With Error (LWE). To solve this problem, this paper proposed a Ciphertext-Policy Attribute-Based Encryption (CP-ABE) scheme from a more lightweight ideal lattice classes- Ring-Learning with Errors (Ring-LWE), that further called as CP-ABER-LWEscheme. Compared to existing R-LWE based ABE scheme, the proposed CP-ABER-LWEis capable to handle a monotone access structure and enjoys collusion resistance properties. We exploited Linear Secret Scheme (LSSS) to express a monotone access structure. For resist to collusion attack, we applied the private key randomization technique to blind the user's private key. The proposed scheme CP-ABER-LWEis further proven to be secure under the Decision Ring-LWEd,q,χproblem in the selective set model.
Access control can selectively restrict access to sensitive information stored by third-party sites on the Internet. Attribute-based encryption (ABE) schemes can strengthen the effective combination of flexibility and operability of access control. They allow one sender to encrypt a message for more than one recipient, and to specify who should be able to decrypt, using attributes alone. Since 2005, many powerful ABE schemes have been presented, but there are two types of problem that haven't be efficiently resolved so far. On the one hand, as practical extension of identity-based encryption (IBE) schemes, ABE schemes are also confronted with key escrow problem. On the other hand, attribute set belonging to one user is usually monitored by different authorities in this era of collaboration. Multi-authority ABE (MA-ABE) schemes can simultaneously resolve these problems, but now they have not been thoroughly investigated yet. More precisely, MA-ABE schemes against quantum attack are the main barrier of the development of ABE schemes in a 'post-quantum' world. In this paper, we firstly present a MA-ABE scheme from lattices, in which identities of users are authenticated by a central authority, which improves the efficiency of authentication. Furthermore, different attribute private keys are still distributed by different authorities, and the central authority cannot obtain any secret information of other attribute authorities, which resolves key escrow problem to some extent. In MAABE, attribute private keys belonging to one user are generated by different authorities, and how to ensure correct decryption is one of the crux of schemes. Our scheme gives a simple solution, and each user's attribute private keys are combined using sharing of common public information to automatically realize correct decryption. To our best knowledge, this is the first MA-ABE scheme from lattices, and it is more efficient than the MA-ABE presented by Melissa Chase. Finally, we present a multi-authority large universe ABE scheme, in which the sizes of the public key and the ciphertext are only relative to the number of the attribute authorities, and a user will be able to decrypt a ciphertext if and only if he has at least tK attributes from each authority K.
In Ciphertext Policy Attribute-Based Encryption (CP-ABE) system, a set of attributes is associated with the private keys of each user. Also, the ciphertext is attached with a policy which is defined over that set of attributes. A user can decrypt the ciphertext if the ciphertext’s policy is satisfied by the attributes associated hith her private key. Traditional CP-ABE schemes, based on number theoretic problems, rely on a trustworthy central authority. But in many distributed applications it is expected that such authorities should be decentralized to avoid the risks of single-point failure. While the number theory-based hardness problems are prone to quantum attacks, lattice-based hardness problems can resist such attacks. In this paper, we construct a Decentralized Ciphertext-Policy Attribute-Based Encryption (DCP-ABE) scheme. Under this scheme, any participating entity can act as an authority by creating a public key. The athority utilizes the users’ attributes to generate the private keys for them. Any user can encrypt data in terms of any monotone access structure over attributes issued from any chosen set of authorities. Hence the protocol does not depend on any central authority. We utilize Learning With Errors over Rings (R-LWE) as the underlying hardness assumption for te protocol. The proposed post-quantum protocol achieves security under selective-set model whereby adversaries are allowed to corrupt any authority only statically through adaptive key queries.