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Paper: The Direction of Updatable Encryption does not Matter Much

Authors:
Yao Jiang
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DOI: 10.1007/978-3-030-64840-4_18
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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.
Video from ASIACRYPT 2020
BibTeX
@article{asiacrypt-2020-30658,
  title={The Direction of Updatable Encryption does not Matter Much},
  booktitle={Advances in Cryptology - ASIACRYPT 2020},
  publisher={Springer},
  doi={10.1007/978-3-030-64840-4_18},
  author={Yao Jiang},
  year=2020
}