Showing papers by "Adam O'Neill published in 2007"

Deterministic and efficiently searchable encryption

Abstract: We present as-strong-as-possible definitions of privacy, and constructions achieving them, for public-key encryption schemes where the encryption algorithm is deterministic. We obtain as a consequence database encryption methods that permit fast (i.e. sub-linear, and in fact logarithmic, time) search while provably providing privacy that is as strong as possible subject to this fast search constraint. One of our constructs, called RSA-DOAEP, has the added feature of being length preserving, so that it is the first example of a public-key cipher. We generalize this to obtain a notion of efficiently-searchable encryption schemes which permit more flexible privacy to search-time trade-offs via a technique called bucketization. Our results answer much-asked questions in the database community and provide foundations for work done there.

Ordered Multisignatures and Identity-Based Sequential Aggregate Signatures, with Applications to Secure Routing.

Abstract: We construct two new multiparty digital signature schemes that allow multiple signers to sequentially produce a compact, fixed-length signature. First, we introduce a new primitive that we call ordered multisignatures (OMS), which allows signers to attest to a common mes- sage as well as the order in which they signed. Our OMS construction substantially improves computational efficiency and scalability over any existing scheme with suitable functionality. Second, we design a new identity-based sequential aggregate signature scheme, where signers can attest to different messages and signature verification does not require knowledge of tradi- tional public keys. The latter property permits savings on bandwidth and storage as compared to public-key solutions. In contrast to the only prior scheme to provide this functionality, ours offers improved security that does not rely on synchronized clocks or a trusted first signer. We provide formal security definitions and support the proposed schemes with security proofs under appropriate computational assumptions. We focus on potential applications of our schemes to secure network routing, but we believe they will find many other applications as well.

Ordered multisignatures and identity-based sequential aggregate signatures, with applications to secure routing

Abstract: We construct new multiparty signature schemes that allow multiple signers to sequentially produce a compact, fixed-length signature simultaneously attesting to the message(s) they want to sign. First, we introduce a new primitive that we call ordered multisignatures (OMS), which allow signers to attest to a common message as well as the order in which they signed. Our OMS construction substantially improves computational efficiency over any existing scheme with comparable functionality. Second, we design a new identity-based sequential aggregate signature scheme, where signers can attest to different messages and signature verification does not require knowledge of traditional public keys. The latter property permits savings on bandwidth and storage as compared to public-key solutions. In contrast to the only prior scheme to provide this functionality, ours offers improved security that does not rely on synchronized clocks or a trusted first signer. Security proofs according to the corresponding security definitions and under appropriate computational assumptions are provided for all the proposed schemes. We give several applications of our schemes to secure network routing, and we believe that they will find many other applications as well.

Provably-secure schemes for basic query support in outsourced databases

Abstract: In this paper, we take a closer look at the security of out-sourced databases (aka Database-as-the-Service or DAS), a topic of emerging importance. DAS allows users to store sensitive data on a remote, untrusted server and retrieve desired parts of it on request. At first we focus on basic, exact-match query functionality, and then extend our treatment to prefix-matching and, to a more limited extent, range queries as well. We propose several searchable encryption schemes that are not only practical enough for use in DAS in terms of query-processing efficiency but also provably-provide privacy and authenticity of data under new definitions of security that we introduce. The schemes are easy to implement and are based on standard cryptographic primitives such as block ciphers, symmetric encryption schemes, and message authentication codes. As we are some of the first to apply the provable-security framework of modern cryptography to this context, we believe our work will help to properly analyze future schemes and facilitate further research on the subject in general.