SoK: Cryptography for neural networks

With the advent of big data technologies which bring better scalability and performance results, machine learning (ML) algorithms become affordable in several different applications and areas. The use of large volumes of data to obtain accurate predictions unfortunately come with a high cost in terms of privacy exposures. The underlying data are often personal or confidential and, therefore, need to be appropriately safeguarded. Given the cost of machine learning algorithms, these would need to be outsourced to third-party servers, and hence protection of the data becomes mandatory. While traditional data encryption solutions would not allow accessing the content of the data, these would, nevertheless, prevent third-party servers from executing the ML algorithms properly. The goal is, therefore, to come up with customized ML algorithms that would, by design, preserve the privacy of the processed data. Advanced cryptographic techniques such as fully homomorphic encryption or secure multi-party computation enable the execution of some operations over protected data and, therefore, can be considered as potential candidates for these algorithms. However, these techniques incur high computational and/or communication costs for some operations. In this paper, we propose a Systematization of Knowledge (SoK) whereby we analyze the tension between a particular ML technique, namely, neural networks (NN), and the characteristics of relevant cryptographic techniques.