Nowadays, emerging technologies such as smart terminals, cloud computing, and the Internet of Things are developing rapidly. The "One-to-one" encrypted transmission method is difficult to meet the communication needs in complex network environments due to high computational costs. Broadcast encryption technology can provide data encryption protection during information sharing among multiple users. However, most of the existing schemes are based on bilinear groups, which cannot resist quantum computing attacks. And these schemes also suffer from the key escrow problem. For this reason, a novel distributed broadcast encryption scheme is proposed based on the Learning with Errors (LWE) difficulty assumption on the lattice. The scheme avoids key interaction negotiation among users by introducing a public key bulletin board. Meanwhile, the scheme solves the security problem caused by the authoritative user's complete mastery of the user's private key.
Nowadays, emerging technologies such as smart terminals, cloud computing, and the Internet of Things are developing rapidly. The "One-to-one" encrypted transmission method is difficult to meet the communication needs in complex network environments due to high computational costs. Broadcast encryption technology can provide data encryption protection during information sharing among multiple users. However, most of the existing schemes are based on bilinear groups, which cannot resist quantum computing attacks. And these schemes also suffer from the key escrow problem. For this reason, a novel distributed broadcast encryption scheme is proposed based on the Learning with Errors (LWE) difficulty assumption on the lattice. The scheme avoids key interaction negotiation among users by introducing a public key bulletin board. Meanwhile, the scheme solves the security problem caused by the authoritative user's complete mastery of the user's private key.
Attribute-based encryption is useful for one-to-many encrypted message sending. However, most attribute-based encryption schemes authorize and issue attributes to users by a single authority. Such a scenario conflicts with practical requirements and may cause the key-escrow problem. Hence, decentralization of authority is a critical issue in attribute-based encryption. Besides, dynamic membership management is another important issue in attribute-based encryption. With dynamic membership management, a system may update the user’s attributes without affecting other users, making the system more flexible and practical. On the other hand, with the rapid development of quantum computers nowadays, encryption schemes based on traditional mathematical problems are at the risk of quantum attacks. Among the existing quantum-resistant mathematical architectures, lattice-based cryptography is the most widely studied. Thus, we propose a multi-authority attribute-based encryption scheme with dynamic membership from lattices to solve the above problems. Moreover, we also formally prove the security of the proposed scheme under the decisional learning with errors assumption.
Multi-Writer Searchable Encryption, also known as public-key encryption with keyword search(PEKS), serves a wide spectrum of data sharing applications. It allows users to search over encrypted data encrypted via different keys. However, most of the existing PEKS schemes are built on classic security assumptions, which are proven to be untenable to overcome the threats of quantum computers. To address the above problem, in this paper, we propose a lattice-based searchable encryption scheme from the learning with errors (LWE) hardness assumption. Specifically, we observe that the keys of each user in a basic scheme are composed of large-sized matrices and basis of the lattice. To reduce the complexity of key management, our scheme is designed to enable users to directly use their identity for data encryption. We present several optimization techniques for implementation to make our design nearly practical. For completeness, we conduct rigorous security, complexity, and parameter analysis on our scheme, and perform comprehensive evaluations at a commodity machine. With a scenario of 100 users, the cost of key generation for each user is 125s, and the cost of searching a document with 1000 keywords is 13.4ms.
In this paper, a hierarchical identity-based broadcast encryption scheme is proposed based on the learning with errors problem, which is a classic hard problem on lattices. In the proposed scheme, each user's identity is associated with a lattice matrix, then the relationship between the lattice and its sub lattice could easily represent the hierarchical identity construction. Short basis of a lattice can function as a private key of a user, so based on the Sample Basis algorithm the private key of each level's user can be derived. The security proof of our proposed scheme is also given in this paper, which is IND-CCA2 secure against the attacks by outsider users and FS-CCA secure against the attacks by authorized receivers. In addition, compared with the broadcast encryption scheme based on the bilinear mapping, the scheme in this paper is more efficient in the encryption and decryption.
- Broadcast encryption helps a sender to securely distribute messages to a dynamically changing set of users over an uncertainty channel. The broadcast encryption scheme needs a trusted party to distribute decoded keys. Group key agreement (GKA) protocols set up a group of members to negotiate a common encryption key via open networks so that only the group members can decrypt the texts and the contributory broadcast encryption (Con BE) can enable the sender to send message to particular member of the group but, it do not offer a fully trusted third-party to set up the system and Existing GKA protocols does not handle sender/member changes effectively. We proposed Arbitrary Topology Generalization and Identity-based Broadcast Encryption (ATIBE) scheme. The scheme holds a Private Key Generator (PKG). The PKG generates private keys from users’ identities by using a master secret key (MSK). The PKG also strengthen the public broadcast encryption key and distributes information of decryption keys to users. This scheme allows avoiding the neighbors’ communication problems, efficient encryption/decryption and only one round is requires setting up the public group. In addition to this proxy re-encryption scheme is used to improve the security level. This proposed scheme establishes secure Broadcast channels and provides a secure numerous emerging distributed computation applications.
Proxy re-encryption plays an important role for data security in cloud computing and big data, but the traditional re-encryption scheme based on the classical number theory problem cannot resist quantum attack, and the lattice-based cryptosystem has been proved to have the ability to resist quantum attack, so the lattice-based re-encryption scheme has always been a research hotspot. In view of the problem that collusion-resistance and multi-hop cannot be satisfied at the same time in existing schemes, this paper proposes a new identity-based proxy re-encryption scheme on lattice. Firstly, the scheme uses trapdoors as private keys to achieve one-way anti-collusion. In addition, we construct a variant of Learning with Errors (LWE), which uses a convert algorithm to transform the user matrix and replace the vector with a uniform matrix, so that the scheme can meet the requirements of multi-hop and encrypt multiple bits of messages at one time. Theoretical analysis and experimental simulation prove that the security of the new scheme can be reduced to a decision LWE problem, which can reach the IND-sID-CPA security in the standard model and can improve the encryption efficiency while ensuring the security.
In public-key encryption, a long-term private key can be an easy target for hacking and deserves extra protection. One way to enhance its security is to share the long-term private key among multiple (say n) distributed servers; any threshold number (t, t ≤ n) of these servers are needed to collectively use the shared private key without reconstructing it. As a result, an attacker who has compromised less than t servers will still not be able to reconstruct the shared private key. In this thesis, we studied threshold decryption schemes for lattice-based public-key en- cryption, which is one of the most promising post-quantum public-key encryption schemes. We developed threshold decryption schemes for Stinson’s, the standard NTRU, and NTRU with Ring Learning with Errors (R-LWE) cryptosystems. Prototype implementations were developed for validating the functionality of these threshold decryption schemes. Our de- signs achieve heuristic security, and its security is supported by mechanisms similar to that of R-LWE.