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Outsourced Cloud Storage and Dynamic Sharing: Efficient Time-Bound Access Control
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DOI：10.1109/TIFS.2025.3650373.png)
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Abstract
En 中文
Cloud storage has become the most attractive way to achieve data sharing by setting flexible access policies. Cryptographic tools are considered the most popular approach to protecting the privacy of data stored on the cloud. Dividing data into different classes plays a significant role in cloud storage, making data organization more methodical and data sharing more expressive and efficient. Unfortunately, current data sharing solutions either neglect data classification or suffer from data leakage. Specifically, shared keys can decrypt newly added encrypted data within the same class, and have key abuse issues where shared keys are untraceable once sold. In this work, we propose a time-bound data sharing system that addresses all these issues simultaneously. In our scheme, data is divided into different classes and encrypted according to its class and associated time period. Decryption keys for a set of chosen data classes can be aggregated into a single key, allowing users to decrypt multiple ciphertexts whose classes are within the set; while other encrypted data with classes outside the set remain confidential. Moreover, the aggregate key is time-bound which can only decrypt the ciphertexts generated before the embedded time period, ensuring it cannot access newly added encrypted data. The key size is independent of the chosen class set size and is only logarithmic in the bit length of the time period used. For each sharing, the shared aggregate key is different. In the event of data leakage or key selling, the data provider can identify the responsible users. We provide formal security analysis of our system and evaluate its performance through experiments. The results demonstrate that our system is highly efficient in terms of shared keys. It provides a practical solution for achieving efficient and dynamic data sharing in cloud storage.
Keywords:
Cloud storage
dynamic data sharing
short keys
time-bound
traceability
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