Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
We study the problem of authenticating the content and creation time of documents generated by an organization and retained in archival storage. Recent regulations (e.g., the Sarbanes-Oxley act and the Securities and Exchange Commission... more
We study the problem of authenticating the content and creation time of documents generated by an organization and retained in archival storage. Recent regulations (e.g., the Sarbanes-Oxley act and the Securities and Exchange Commission rule) mandate secure retention of important business records for several years. We provide a mechanism to authenticate bulk repositories of archived documents. In our approach, a space efficient local data structure encapsulates a full document repository in a short (e.g., 32-byte) digest. Periodically registered with a trusted party, these commitments enable compact proofs of both document creation time and content integrity. The data structure, an append-only persistent authenticated dictionary, allows for efficient proofs of existence and non-existence, improving on state-of-the-art techniques. We confirm through an experimental evaluation with the Enron email corpus its feasibility in practice.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
We propose a new keyword-based Private Information Retrieval (PIR) model that allows private modification of the database from which information is requested. In our model, the database is distributed over n servers, any one of which can... more
We propose a new keyword-based Private Information Retrieval (PIR) model that allows private modification of the database from which information is requested. In our model, the database is distributed over n servers, any one of which can act as a transparent interface for clients. We present protocols that support operations for accessing data, focusing on privately appending labelled records to the database (push) and privately retrieving the next unseen record appended under a given label (pull). The communication complexity between the client and servers is independent of the number of records in the database (or more generally, the number of previous push and pull operations) and of the number of servers. Our scheme also supports access control oblivious to the database servers by implicitly including a public key in each push, so that only the party holding the private key can retrieve the record via pull. To our knowledge, this is the first system that achieves the following properties: private database modification, private retrieval of multiple records with the same keyword, and oblivious access control. We also provide a number of extensions to our protocols and, as a demonstrative application, an unlinkable anonymous communication service using them.