Aimed at strengthening data protection and utilization in fields from healthcare and public services to finance
Hitachi, seeking to counter the growing risk that conventional encryption technology will be broken by quantum computers, which are progressing toward practical implementation, has developed new encryption technology capable of high-speed searching,*1 based on quantum-resistant public key encryption*2 called lattice-based cryptography.*3 Employing the newly developed technology, large amounts of data encrypted and stored on a cloud server can be searched while still in encrypted state, at ten times the speed of earlier quantum-resistant public key searchable encryption technology. Moreover, statistical processing of the encrypted data can be achieved safely. In this way, the data can be put to much wider uses, such as performing medical data analysis, while ensuring data safety.
Hitachi will aim for use of this technology in healthcare, public services, finance and many other fields, helping to strengthen the protection and utilization of customer data.
Figure 1. Taking advantage of this technology for safe use of medical data
Services that collect and analyze personal information and other confidential information on cloud servers have seen growing use in recent years. As quantum computers come closer to practical implementation, however, there are growing concerns about the risk that conventional encryption may be broken. These concerns have given rise to demands for new encryption methods resistant to attacks that use quantum computers. Existing quantum-resistant encryption methods, however, have high computational processing loads, posing problems for efficient searching of large volumes of data. An additional risk is that of privacy leaks from statistical processing using the search results.
Responding to these issues, Hitachi has developed high-speed searchable encryption technology based on lattice-based cryptography, which is a quantum-resistant public key encryption method, along with privacy-protective confidential statistical computation technology using the new encryption method. The main features of the newly developed technology are as follows.
1. Along with ensuring high safety, achieves high-speed searching by reducing the vector dimension
The number of vector dimensions used in search processing has been successfully reduced even while conducting the same detailed safety analysis as with conventional methods, at no loss of safety. The result is search speed ten times faster than when using conventional lattice-based cryptography, enabling highly efficient searching of large volumes of data.
2. Realizes confidential statistical computation by means of safe data extraction
A concern from the standpoint of privacy protection is that when the amount of data being handled is small, it may be possible to infer the original data by statistical analysis. An issue for safe statistical computation is how to extract data of at least a certain amount suitable for statistical processing. Hitachi therefore developed technology, using secret sharing,*4 that converts the search results to data that can be statistically processed only when the results gathered are above a certain number. This technology was then combined with homomorphic encryption*5 to realize statistical computation of data while it is still in encrypted state. These technologies promise to expand the scope of data use, such as enabling analysis of medical data while protecting patient privacy.
Hitachi will continue with R&D aimed at practical implementation of this technology in fields such as healthcare, public services, and finance, contributing to the safe and efficient use of data through the development of security technology for the quantum computer era.
*1 Encryption technology enabling searches for text containing search keywords with the searched text and keywords still in encrypted state. Using searchable encryption eliminates the need for a decryption key on the cloud server side, reducing the risk of information leaks.
*2 An encryption method using different keys for encryption and decryption.
*3 A method that mathematically expresses regular patterns in a basic array of vectors and uses these expressions for encryption. The public key encryption method standardized by the U.S. National Institute of Standards and Technology (NIST) is one type of lattice-based cryptography. When high-dimensional patterns are used, it is assumed that the encryption will be hard to break even using a quantum computer. In the figure below, the regularly arrayed intersections (red dots) are lattice points. In lattice-based cryptography, these lattice points are expressed mathematically and used for encryption. All lattice points can be expressed as an integral linear combination of generating vectors (yellow arrows). Lattice-based cryptography takes advantage of the difficulty of finding a short vector in a randomly generated lattice.
Figure 2. Illustration of a lattice used in lattice-based cryptography
*4 Technology that splits confidential information into multiple shares, enabling the information to be decrypted only when a certain number of shares have been assembled, and rendering decryption impossible without the requisite number of shares.
*5 Encryption technology enabling computational processing of data while it is still in encrypted state. With this technology, addition, multiplication, and other operations on encrypted data can be performed on a cloud server without a decryption key.
For more information, use the inquiry form below to contact the Research & Development Group, Hitachi, Ltd. Please make sure to include the title of the article.
https://www8.hitachi.co.jp/inquiry/hitachi-ltd/hqrd/news/en/form.jsp
