Abstract:

We are specifically concerned with scenarios in which multimedia data is stored once on the server and the same data is queried by multiple parties. We propose a framework for privacy preserving querying, in which encryption is performed only once, and the ciphertexts are stored on a database server. Rather than using public-key homomorphic cryptosystems, the parties querying the database first derive an "attribute" from their query signal. They can decrypt the server's ciphertext only if their attribute satisfies a specified mathematical condition. This query-specific decryption capability makes attribute based cryptography a vital addition to the secure signal processor's toolkit. We give an example of a construction for privacy preserving querying, in which a client can privately retrieve an image from the server if attribute vectors extracted from the server's and client's images are close enough in Euclidean distance.