Despite their limited put/get interface, simple hosted storage services are becoming very popular. Many companies and individuals are using them to store and backup data. Recent work has demonstrated that there are some benefits to building file systems on top of such abstractions. However, the available API lacks some features that could prove beneficiary in building distributed storage systems on top of such services. In this project I investigated extending the interface of Amazon's S3 storage service to allow for more powerful capabilities such as locking, multi-key transactions, and ensuring data integrity.