A Private and Anonymous Data Repository Service

This paper describes a security problem involving an online data repository which acts as a proxy for multiple companies allowing their customers to perform online services (e.g., pay invoices). The repository´s host is trusted to honestly fulfil its duties in maintaining the data in a manner consistent with each companies´ required services. However, the information stored by the repository remains private in that the repository´s host cannot openly read any companies´ operational data, nor does it learn the identities of any companies´ customers. We contrast several approaches describing their viability for web deployment using existing technologies. This is a fundamentally new security problem with no established literature or clearly defined cryptographic solution. The project originated from a commercial attempt to design a secure online data archive that allows a customer to pay and view invoices online.