Proofs of Retrievability (PoRs) are protocols which allow a client to store data remotely and to efficiently ensure, via audits, that the entirety of that data is still intact. A dynamic PoR system also supports efficient retrieval and update of any small portion of the data. We propose new, simple protocols for dynamic PoR that are designed for practical efficiency, trading decreased persistent storage for increased server computation, and show in fact that this tradeoff is inherent via a lower bound proof of time-space for any PoR scheme. Notably, ours is the first dynamic PoR which does not require any special encoding of the data stored on the server, meaning it can be trivially composed with any database service or with existing techniques for encryption or redundancy. Our implementation and deployment on Google Cloud Platform demonstrates our solution is scalable: for example, auditing a 1TB file takes just less than 5 minutes and costs less than $0.08 USD. We also present several further enhancements, reducing the amount of client storage, or the communication bandwidth, or allowing public verifiability, wherein any untrusted third party may conduct an audit.

翻译：可检索性证据(PoRs)是允许客户远程存储数据并通过审计有效确保这些数据完整完整的协议。动态PoR系统还支持有效检索和更新数据的任何一小部分。我们为动态PoR提出了新的简单协议,这些协议的设计是为了提高实际效率,为增加服务器计算而降低持续存储量,并表明这种权衡是通过任何PoR计划的较低约束时间空间证明所固有的。值得注意的是,我们是第一个不需要对服务器上存储的数据作任何特殊编码的动态PoR,这意味着它可能与任何数据库服务或现有加密或冗余技术组成微不足道。我们在谷歌云平台上的实施和部署表明我们的解决方案是可扩展的:例如,审计1TB文件只需5分钟,费用不到0.08美元。我们还提出若干进一步的改进,减少客户存储量或通信带宽,或允许公众核查,其中任何不信任的第三方都可以进行审计。