Git services such as GitHub, have been widely used to manage projects and enable collaborations among multiple entities. Just as in messaging and cloud storage, where end-to-end security has been gaining increased attention, such a level of security is also demanded for Git services. Content in the repositories (and the data/code supply-chain facilitated by Git services) could be highly valuable, whereas the threat of system breaches has become routine nowadays. However, existing studies of Git security to date (mostly open source projects) suffer in two ways: they provide only very weak security, and they have a large overhead.

The cloud has become pervasive, and we ask: how can we protect cloud data against the cloud itself? For secure user-to-user communication via a cloud server, End-to-End encryption has been formally studied, building on existing TLS channels without requiring new primitives. However, enabling user-to-same-user secure outsourced data storage–solving the analogous problem of “privacy from the server” while (1) relying on existing infrastructure and (2) supporting user mobility, remains open. Existing proposals, like password-protected secret sharing, target the same goal but are incompatible with existing cloud storage services. Specifically, they lack the simplicity needed to directly utilize existing cloud storage without requiring changes on the cloud side. Here, we propose a novel system for securely storing private data in existing cloud storage with the help of a key server (necessary, given the requirements). In our system, user data is secure against threats from the cloud server, the key server, and illegitimate users. Only the legitimate user can access the data on any device using a correct passphrase. Most importantly, our system does not require the storage server to support any newly programmable operations. Moreover, leveraging the existing App login, our system requires only one passphrase, which never leaves the user’s device and remains hidden from both servers. The security is proved under formal models, and its efficiency is demonstrated by experiments conducted on Amazon S3. Notably, a preliminary variant, based on our principles, was deployed by Snapchat in their My Eyes Only module, serving hundreds of millions of users!

Summary As the value of data has received considerable attention, data trading shows broad market prospects. The existing data trading methods, including private trades and centralized trades, have high risks regarding transaction security and data protection. To solve this problem, we propose a decentralized trading solution for open fair data trading by deploying the smart contract on the blockchain network. The data for sale are encrypted and stored on the distributed storage platform but not directly on the blockchain network. Because the trading content is the decryption key of the data, the proposed new method can alleviate the storage pressure of the blockchain by reducing the transaction cost. We conduct a security analysis which shows that our scheme achieves secure, practical, open, and fair trading. We implement our trading contract with solidity and test it on the Ethereum's test network, and extensive experiments demonstrate desirable feasibility of our proposal.