As an important security property of cloud storage, data integrity has not been sufficiently studied under the multiwriter model, where a group of users work on shared files collaboratively and any group member can update the data by modification, insertion, and deletion operations. Existing works under such multi-writer model would bring large storage cost to the third-party verifiers. Furthermore, to the best of our knowledge, none of the existing works for shared files supports fully dynamic operations, which implies that users cannot freely perform the update operations. In this paper, we propose the first public auditing scheme for shared data that supports fully dynamic operations and achieves constant storage cost for the verifiers. Our scheme, named PRAYS, is boosted by a new paradigm for remote data integrity checking. To implement the new paradigm, we proposed a specially designed authenticated structure, called blockless Merkle tree, and a novel cryptographic primitive, called permission-based signature. Extensive evaluation demonstrates that PRAYS is as efficient as the existing less-functional solutions. We believe that PRAYS is an important step towards designing practical multiwriter cloud storage systems.

中文翻译：

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云中面向群组的动态可证明数据所有权

作为云存储的一个重要安全属性，数据完整性在多写入器模型下尚未得到充分研究，即一组用户协同处理共享文件，任何组成员都可以通过修改、插入和删除操作来更新数据。这种多作者模式下的现有作品会给第三方验证者带来巨大的存储成本。此外，据我们所知，现有的共享文件作品均不支持完全动态操作，这意味着用户无法自由执行更新操作。在本文中，我们提出了第一个共享数据的公共审计方案，该方案支持完全动态操作并为验证者实现恒定的存储成本。我们名为 PRAYS 的方案受到远程数据完整性检查的新范式的推动。为了实现新范式，我们提出了一种专门设计的认证结构，称为无块默克尔树，以及一种新颖的加密原语，称为基于许可的签名。广泛的评估表明 PRAYS 与现有的功能较少的解决方案一样有效。我们相信 PRAYS 是朝着设计实用的多写入器云存储系统迈出的重要一步。