1 (State Key Laboratory of Mathematical Engineering and Advanced Computing , Zhengzhou 450001) Abstract: Fully homomorphic is an encryption scheme that allows for data to be stored and processed in an encrypted format, which gives the cloud provider a solution to host and process data without even knowing what the message is. In previous identity-based homomorphic encryption scheme, computing efficiency is complicated and expensive. In this work, based on Regev’s work, we propose a sampling trapdoor one-way function in arbitrary cyclotomic rings [ ] ( ) / 1 n R X x = + Z . Then construct a leveled identity-based homomorphic encryption scheme from ring learning with errors, which has advantage in computational efficiency and key management, by using user’s identity as the unique public key. This scheme is proved IND-CPA secure in the random oracle model, relied to hardness of decision ring learning with errors problem.
1 (State Key Laboratory of Mathematical Engineering and Advanced Computing , Zhengzhou 450001) Abstract: Fully homomorphic is an encryption scheme that allows for data to be stored and processed in an encrypted format, which gives the cloud provider a solution to host and process data without even knowing what the message is. In previous identity-based homomorphic encryption scheme, computing efficiency is complicated and expensive. In this work, based on Regev’s work, we propose a sampling trapdoor one-way function in arbitrary cyclotomic rings [ ] ( ) / 1 n R X x = + Z . Then construct a leveled identity-based homomorphic encryption scheme from ring learning with errors, which has advantage in computational efficiency and key management, by using user’s identity as the unique public key. This scheme is proved IND-CPA secure in the random oracle model, relied to hardness of decision ring learning with errors problem.
Abstract Data can be stored and processed in an encrypted format using fully homomorphic encryption, which makes cloud computing provider can process data well without even knowing data information. However, most existing homomorphic encryption schemes based on ring learning with errors, focus on the special classes of rings, such as power-of-two cyclotomic rings, which significantly limits its application efficiency in cloud computing. Therefore, in this letter, to solve this problem above, an efficient fully homomorphic encryption scheme is proposed based on ring learning with errors in arbitrary cyclotomic rings. Particularly, a “somewhat homomorphic encryption” scheme is firstly proposed based on ring learning with errors. A novel fully homomorphic encryption scheme is further presented using key-switching. With theoretical and experimental verification, the proposed scheme has advantage of high efficiency of encryption and decryption. The security of our scheme strictly reduces to hardness of decision ring learning with errors problem in the random oracle model.
The efficiency of fully homomorphic encryption is a big question at present. To improve efficiency of fully homomorphic encryption, we use the technique of packed ciphertext to construct a multi-bit fully homomorphic encryption based on Learning with Errors problem. Our scheme has a short public key. Since our fully homomorphic encryption scheme builds on the basic encryption scheme that choose Learning with Errors samples from Gaussian distribution and add Gaussian error to it, which result in that the number of Learning with Errors samples decrease from 2nlogq to n+1. We prove that our fully homomorphic encryption scheme is feasible and its security relies on the hardness of Learning with Errors problem. In addition we adapt the optimization for the process of key switching from GHS13 and formal this new process of key switching for multi-bit fully homomorphic encryption. At last, we analyze the concert parameters and compare these parameters between our scheme and GHS13 scheme. The data show that our scheme has public key smaller by a factor of about logq than it in GHS13 scheme.
Fully homomorphic encryption (FHE) has important applications in cloud computing. However, almost all fully homomorphic encryption schemes share two common flaws that they all use large-scale secret keys and some operations are inefficient. In this paper, the 'special b' variant of the learning with errors problem (bLWE) is presented, and helps us construct the first circularly secure key switching process which can replace the key switching process and similar re-linearisation process used by the existing FHE schemes. Then, we present an efficient FHE. Compared with Brakerski's scheme, our scheme reduces L secret keys to one and is more efficient. Finally, we prove the chosen-plaintext attack (CPA) security of the fully homomorphic scheme and the circular security of key switching process in standard model under the learning with errors problem (LWE) assumption.
Since its proposal by Regev in 2005, the Learning With Errors (LWE) problem was used as the underlying problem for a great variety of schemes. Its applications are many-fold, reaching from basic and highly practical primitives like key exchange, public-key encryption, and signature schemes to very advanced solutions like fully homomorphic encryption, group signatures, and identity based encryption. One of the underlying reasons for this fertility is the flexibility with that LWE can be instantiated. Unfortunately, this comes at a cost: It makes selecting parameters for cryptographic applications complicated. When selecting parameters for a new LWE-based primitive, a researcher has to take the influence of several parameters on the efficiency of the scheme and the runtime of a variety of attacks into consideration. In fact, the missing trust in the concrete hardness of LWE is one of the main problems to overcome to bring LWE-based schemes to practice. This thesis aims at closing the gap between the theoretical knowledge of the hardness of LWE, and the concrete problem of selecting parameters for an LWE-based scheme. To this end, we analyze the existing methods to estimate the hardness of LWE, and introduce new estimation techniques where necessary. Afterwards, we show how to transfer this knowledge into instantiations that are at the same time secure and efficient. We show this process on three examples: - A highly optimized public-key encryption scheme for embedded devices that is based on a variant of Ring-LWE. - A practical signature scheme that served as the foundation of one of the best lattice-based signature schemes based on standard lattices. - An advanced public-key encryption scheme that enjoys the unique property of natural double hardness based on LWE instances similar to those used for fully homomorphic encryption.
Fully homomorphic encryption (FHE) has important applications in cloud computing. However, almost all fully homomorphic encryption schemes share two common flaws that they all use large-scale secret keys and some operations are inefficient. In this paper, the 'special b' variant of the learning with errors problem (bLWE) is presented, and helps us construct the first circularly secure key switching process which can replace the key switching process and similar re-linearisation process used by the existing FHE schemes. Then, we present an efficient FHE. Compared with Brakerski's scheme, our scheme reduces L secret keys to one and is more efficient. Finally, we prove the chosen-plaintext attack (CPA) security of the fully homomorphic scheme and the circular security of key switching process in standard model under the learning with errors problem (LWE) assumption.
With the development of quantum theory, traditional encryption algorithms are facing enormous challenges. Once quantum computers are available, existing encryption systems will no longer be secure. The lattice cipher is proven by theory to be a new type of encryption scheme, which can resist quantum algorithm. It has the property of fast computing speed and small space occupation, hence, it has become a hot issue in today??s research. The identity-based encryption scheme can improve the utilization of storage space and facilitate user public key management. Consequently, this paper based on the hard problem of learning with errors (LWE), constructs an identity-based matrix encryption scheme at first, then applies the improved key switching technology to reduce the dimension of homomorphic ciphertext to normal, and uses the mode conversion technique to reduce noise, realizing matrix homo-morphic operation, and getting an identity-based matrix (level) fully homomorphic encryption scheme. The scheme uses matrices as the storage structure, which has greatly improved the processing capability compared to other single-bit schemes. The scheme not only satisfies the addition and Hadamard product of the matrix, but also supports matrix dot multiplication. The experimental results show that compared with other methods, the improved key switching technology in this paper inputs less noise. Through the difficulty of the LWE problem, it is proven that the scheme satisfies IND-sID-CPA (indistinguishability-selective identity-chosen plaintext attack).