[Resource Topic] 2020/622: The Direction of Updatable Encryption does not Matter Much

Welcome to the resource topic for 2020/622

Title:
The Direction of Updatable Encryption does not Matter Much

Authors: Yao Jiang

Abstract:

Updatable encryption schemes allow for key rotation on ciphertexts. A client outsourcing storage of encrypted data to a cloud server can change its encryption key. The cloud server can update the stored ciphertexts to the new key using only a token provided by the client. This paper solves two open problems in updatable encryption, that of uni-directional vs. bi-directional updates, and post-quantum security. The main result in this paper is to analyze the security notions based on uni- and bi-directional updates. Surprisingly, we prove that uni- and bi-directional variants of each security notion are equivalent. The second result in this paper is to provide a new and efficient updatable encryption scheme based on the Decisional Learning with Error assumption. This gives us post-quantum security. Our scheme is bi-directional, but because of our main result, this is sufficient.

ePrint: https://eprint.iacr.org/2020/622

Talk: https://www.youtube.com/watch?v=4uZK2J7DaJ0

Slides: https://iacr.org/submit/files/slides/2020/asiacrypt/ac2020/141/slides.pdf

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