Privacy-Enhanced Searches Using Encrypted Bloom Filters

It is often necessary for two or more or more parties that do not fully trust each other to share data selectively. For example, one intelligence agency might be willing to turn over certain documents to another such agency, but only if the second agency requests the specific documents. The problem, of course, is finding out that such documents exist when access to the database is restricted. We propose a search scheme based on Bloom filters and group ciphers such as Pohlig-Hellman encryption. A semi-trusted third party can transform one party's search queries to a form suitable for querying the other party's database, in such a way that neither the third party nor the database owner can see the original query. Furthermore, the encryption keys used to construct the Bloom filters are not shared with this third party. Multiple providers and queries are supported; provision can be made for third-party "warrant servers", as well as "censorship sets" that limit the data to be shared

Approximate Two-Party Privacy-Preserving String Matching with Linear Complexity

Consider two parties who want to compare their strings, e.g., genomes, but do not want to reveal them to each other. We present a system for privacy-preserving matching of strings, which differs from existing systems by providing a deterministic approximation instead of an exact distance. It is efficient (linear complexity), non-interactive and does not involve a third party which makes it particularly suitable for cloud computing. We extend our protocol, such that it mitigates iterated differential attacks proposed by Goodrich. Further an implementation of the system is evaluated and compared against current privacy-preserving string matching algorithms.Comment: 6 pages, 4 figure

Evaluation of Anonymized ONS Queries

Electronic Product Code (EPC) is the basis of a pervasive infrastructure for the automatic identification of objects on supply chain applications (e.g., pharmaceutical or military applications). This infrastructure relies on the use of the (1) Radio Frequency Identification (RFID) technology to tag objects in motion and (2) distributed services providing information about objects via the Internet. A lookup service, called the Object Name Service (ONS) and based on the use of the Domain Name System (DNS), can be publicly accessed by EPC applications looking for information associated with tagged objects. Privacy issues may affect corporate infrastructures based on EPC technologies if their lookup service is not properly protected. A possible solution to mitigate these issues is the use of online anonymity. We present an evaluation experiment that compares the of use of Tor (The second generation Onion Router) on a global ONS/DNS setup, with respect to benefits, limitations, and latency.Comment: 14 page

Distributed Searchable Symmetric Encryption

Searchable Symmetric Encryption (SSE) allows a client to store encrypted data on a storage provider in such a way, that the client is able to search and retrieve the data selectively without the storage provider learning the contents of the data or the words being searched for. Practical SSE schemes usually leak (sensitive) information during or after a query (e.g., the search pattern). Secure schemes on the other hand are not practical, namely they are neither efficient in the computational search complexity, nor scalable with large data sets. To achieve efficiency and security at the same time, we introduce the concept of distributed SSE (DSSE), which uses a query proxy in addition to the storage provider.\ud We give a construction that combines an inverted index approach (for efficiency) with scrambling functions used in private information retrieval (PIR) (for security). The proposed scheme, which is entirely based on XOR operations and pseudo-random functions, is efficient and does not leak the search pattern. For instance, a secure search in an index over one million documents and 500 keywords is executed in less than 1 second

SSARES: Secure Searchable Automated Remote Email Storage

The increasing centralization of networked services places user data at considerable risk. For example, many users store email on remote servers rather than on their local disk. Doing so allows users to gain the benefit of regular backups and remote access, but it also places a great deal of unwarranted trust in the server. Since most email is stored in plaintext, a compromise of the server implies the loss of confidentiality and integrity of the email stored therein. Although users could employ an end-to-end encryption scheme (e.g., PGP), such measures are not widely adopted, require action on the sender side, only provide partial protection (the email headers remain in the clear), and prevent the users from performing some common operations, such as server-side search. To address this problem, we present secure searchable automated remote email storage (SSARES), a novel system that offers a practical approach to both securing remotely stored email and allowing privacy-preserving search of that email collection. Our solution encrypts email (the headers, body, and attachments) as it arrives on the server using public-key encryption. SSARES uses a combination of identity based encryption and bloom filters to create a searchable index. This index reveals little information about search keywords and queries, even against adversaries that compromise the server. SSARES remains largely transparent to both the sender and recipient

A bloom filter based model for decentralized authorization

A decentralized authorization mechanism is proposed that uses Bloom filters to implement authorization delegation. This lightweight mechanism is unlike conventional approaches that typically rely on public key certificates to implement distributed delegation. In taking an approach based on one-way hash functions, the mechanism may be preferable for use in computationally constrained environments where public-key cryptography is not desirable

A bloom filter based model for decentralized authorization

A decentralized authorization mechanism is proposed that uses Bloom filters to implement authorization delegation. This lightweight mechanism is unlike conventional approaches that typically rely on public key certificates to implement distributed delegation. In taking an approach based on one-way hash functions, the mechanism may be preferable for use in computationally constrained environments where public-key cryptography is not desirable