Flattening NTRU for Evaluation Key Free Homomorphic Encryption

We propose a new FHE scheme {\sf F-NTRU} that adopts the flattening technique proposed in GSW to derive an NTRU based scheme that (similar to GSW) does not require evaluation keys or key switching. Our scheme eliminates the decision small polynomial ratio (DSPR) assumption but relies only on the standard R-LWE assumption. It uses wide key distributions, and hence is immune to the Subfield Lattice Attack. In practice, our scheme achieves competitive timings compared to the existing schemes. We are able to compute a homomorphic multiplication in $24.4$~msec and $34.3$~msec for $5$ and $30$ levels, respectively, without amortization. Furthermore, our scheme features small ciphertexts, e.g. $1152$~KB for $30$ levels, and eliminates the need for storing and managing costly evaluation keys. In addition, we present a slightly modified version of F-NTRU that is capable to support integer operations with a very large message space along with noise analysis for all cases. The assurance gained by using wide key distributions along with the message space flexibility of the scheme, i.e. bits, binary polynomials, and integers with a large message space, allows the use of the proposed scheme in a wide array of applications

A Survey on Implementation of Homomorphic Encryption Scheme in Cloud based Medical Analytical System

The privacy of sensitive personal information is more and more important topic as a result of the increased availability of cloud services. These privacy issues arise due to the legitimate concern of a) having a security breach on these cloud servers or b) the leakage of this sensitive information due to an honest but curious individual at the cloud service provider. Standard encryption schemes try to address the ?rst concern by devising encryption schemes that are harder to break, yet they don’t solve the possible misuse of this sensitive data by the cloud service providers. Homomorphic encryption presents a tool that can solve both types of privacy concerns. The clients are given the possibility of encrypting their sensitive information before sending it to the cloud. The cloud will then compute over their encrypted data without the need for the decryption key. By using homomorphic encryption, servers guarantee to the clients that their valuable information to have no problems after being in a difficult situation.

Blind Web Search: How far are we from a privacy preserving search engine?

Recent rapid progress in fully homomorphic encryption (FHE) and somewhat homomorphic encryption (SHE) has catalyzed renewed efforts to develop efficient privacy preserving protocols. Several works have already appeared in the literature that provide solutions to these problems by employing FHE or SHE techniques. In this work, we focus on a natural application where privacy is a major concern: web search. An estimated 5 billion web queries are processed by the world\u27s leading search engines each day. It is no surprise, then, that privacy-preserving web search was proposed as the paragon FHE application in Gentry\u27s seminal FHE paper. Indeed, numerous proposals have emerged in the intervening years that attack various privatized search problems over encrypted user data, e.g. private information retrieval (PIR). Yet, there is no known work that focuses on implementing a completely blind web search engine using an FHE/SHE construction. In this work, we focus first on single keyword queries with exact matches, aiming toward real-world viability. We then discuss multiple-keyword searches and tackle a number of issues currently hindering practical implementation, such as communication and computational efficiency

A Survey on Homomorphic Encryption Schemes: Theory and Implementation

Legacy encryption systems depend on sharing a key (public or private) among the peers involved in exchanging an encrypted message. However, this approach poses privacy concerns. Especially with popular cloud services, the control over the privacy of the sensitive data is lost. Even when the keys are not shared, the encrypted material is shared with a third party that does not necessarily need to access the content. Moreover, untrusted servers, providers, and cloud operators can keep identifying elements of users long after users end the relationship with the services. Indeed, Homomorphic Encryption (HE), a special kind of encryption scheme, can address these concerns as it allows any third party to operate on the encrypted data without decrypting it in advance. Although this extremely useful feature of the HE scheme has been known for over 30 years, the first plausible and achievable Fully Homomorphic Encryption (FHE) scheme, which allows any computable function to perform on the encrypted data, was introduced by Craig Gentry in 2009. Even though this was a major achievement, different implementations so far demonstrated that FHE still needs to be improved significantly to be practical on every platform. First, we present the basics of HE and the details of the well-known Partially Homomorphic Encryption (PHE) and Somewhat Homomorphic Encryption (SWHE), which are important pillars of achieving FHE. Then, the main FHE families, which have become the base for the other follow-up FHE schemes are presented. Furthermore, the implementations and recent improvements in Gentry-type FHE schemes are also surveyed. Finally, further research directions are discussed. This survey is intended to give a clear knowledge and foundation to researchers and practitioners interested in knowing, applying, as well as extending the state of the art HE, PHE, SWHE, and FHE systems.Comment: - Updated. (October 6, 2017) - This paper is an early draft of the survey that is being submitted to ACM CSUR and has been uploaded to arXiv for feedback from stakeholder

Flattening NTRU for Evaluation Key Free Homomorphic Encryption

We propose a new FHE scheme F-NTRU that adopts the flattening technique proposed in GSW to derive an NTRU based scheme that (similar to GSW) does not require evaluation keys or key switching. Our scheme eliminates the decision small polynomial ratio assumption but relies only on the standard R-LWE assumption. It uses wide key distributions, and hence is immune to Subfield Lattice Attack. In practice, our scheme achieves competitive timings compared to the existing schemes. We are able to compute a homomorphic multiplication in 24.4 msec and 76.0 msec for 5 and 30 levels, respectively, without amortization. Furthermore, our scheme features small ciphertexts, e.g. 2376 KB for 30 levels. The assurance gained by using wide key distributions along with the message space flexibility of the scheme, i.e. bits, binary polynomials, and integers with a large message space, allows the use of the proposed scheme in a wide array of applications