Authentic data publication over the Internet1

Abstract

Integrity critical databases, such as financial information used in high-value decisions, are frequently published over the Internet. Publishers of such data must satisfy the integrity, authenticity, and non-repudiation requirements of clients. Providing this protection over public data networks is an expensive proposition. This is, in part, due to the difficulty of building and running secure systems. In practice, large systems can not be verified to be secure and are frequently penetrated. The negative consequences of a system intrusion at the publisher can be severe. The problem is further complicated by data and server replication to satisfy availability and scalability requirements.To our knowledge this work is the first of its kind to give general approaches for reducing the trust required of publishers of large databases. To do this, we separate the roles of data owner and data publisher. With a few digital signatures on the part of the owner and no trust required of a publisher, we give techniques based on Merkle hash trees that publishers can use to provide authenticity and non-repudiation of the answer to database queries posed by a client. This is done without requiring a key to be held in an on-line system, thus reducing the impact of system penetrations. By reducing the trust required of the publisher, our solution is a step towards the publication of large databases in a scalable manner.

Verified Query Results from Hybrid Authentication Trees

“…We compare three different range query verification methods, Authentic Publication proposed by Devanbu, et al in [6], Pang and Tan's verifiable B-tree (VB tree) in [17] and the proposals in this paper. We focus on Client proof overhead and verification cost and then consider the effect of bandwidth.…”

“…A HAT is just a binary search tree with data stored at the leaves, along with a digest procedure that incorporates a fast collision intractable hash function h and an accumulator H. We want to take advantage of the input reordering allowed by an accumulator to avoid checking the entire hash path to the root as done when using Merkle trees as in Authentic Publication [6] and related schemes. However, accumulators have larger output, typically near the 1024 bits of an RSA modulus compared to the 160 bit output of SHA-1, and take longer to verify a value y i against a proof z i for a set value z.…”

“…We follow the general Authentic Publication model [6]: a trusted data Owner relies on an untrusted third party Publisher to respond to Client queries on a data set. First, a trusted Owner computes a digest of the data set (e.g.…”

“…The Owner relies on the untrusted Publisher to process Client database queries. In the related Authentic Publication model [6], the Publisher is assumed to be untrusted, but the Owner is trusted, so Clients use a small digest value computed over the database by the Owner, to verify the query results. The same digest verifies many different queries on the same database.…”

“…This allows the Owner to rely on, presumably cheaper, untrusted resources to handle Client requests. Authentic Publication [6] uses the organization of a tree digest, based on Merkle trees, to provide efficient verification for Clients.…”