Machine learning on (homomorphic) encrypted data is a cryptographic method for analyzing private and/or sensitive data while keeping privacy. In the training phase, it takes as input an encrypted training data and outputs an encrypted model without ever decrypting. In the prediction phase, it uses the encrypted model to predict results on new encrypted data. In each phase, no decryption key is needed, and thus the data privacy is ultimately guaranteed. It has many applications in various areas such as finance, education, genomics, and medical field that have sensitive private data. While several studies have been reported on the prediction phase, few studies have been conducted on the training phase.In this paper, we present an efficient algorithm for logistic regression on homomorphic encrypted data, and evaluate our algorithm on real financial data consisting of 422,108 samples over 200 features. Our experiment shows that an encrypted model with a sufficient Kolmogorov Smirnow statistic value can be obtained in ∼17 hours in a single machine. We also evaluate our algorithm on the public MNIST dataset, and it takes ∼2 hours to learn an encrypted model with 96.4% accuracy. Considering the inefficiency of homomorphic encryption, our result is encouraging and demonstrates the practical feasibility of the logistic regression training on large encrypted data, for the first time to the best of our knowledge.
Highlights d Fast homomorphic encryption enables secure and practical genotype imputations d Secure methods require comparable resources as nonsecure methods d Accuracy of secure methods can be improved using population specific panels
The dual attack is one of the most efficient attack algorithms for learning with errors (LWE) problem. Recently, an efficient variant of the dual attack for sparse and small secret LWE was reported by Albrecht (Eurocrypt 2017), which forces some LWE-based cryptosystems, especially fully homomorphic encryptions (FHE), to change parameters. In this paper, we propose a new hybrid of dual and meet-in-themiddle (MITM) attack, which outperforms the improved variant on the same LWE parameter regime. To this end, we adapt the MITM attack for NTRU due to Odlyzko to LWE and give a rigorous analysis for it. The performance of our MITM attack depends on the relative size of error and modulus, and hence, for a large modulus LWE samples, our MITM attack works well for quite large error. We then combine our MITM attack with Albrecht's observation that understands the dual attack as a dimension-error tradeoff, which finally yields our hybrid attack. We also implement a sage module that estimates the attack complexity of our algorithm upon LWE-estimator, and our attack shows significant performance improvement for the LWE parameter for FHE. For example, for the LWE problem with dimension n = 2 15 , modulus q = 2 628 , and ternary secret key with Hamming weight 64 which is one parameter set used for HEAAN bootstrapping (Eurocrypt 2018), our attack takes 2 112.5 operations and 2 70.6 bit memory, while the previous best attack requires 2 127.2 operations as reported by the LWE-estimator. INDEX TERMS Cryptanalysis, fully homomorphic encryption, learning with errors, meet-in-the-middle.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.