## CryptoDB

### Klaus Kursawe

#### Publications

Year
Venue
Title
2015
EPRINT
2008
EPRINT
In the last years, DNA sequencing techniques have advanced to the point that DNA identification and paternity testing has become almost a commodity. Due to the critical nature of DNA related data, this causes substantial privacy issues. In this paper, we introduce cryptographic privacy enhancing protocols that allow to perform the most common DNA-based identity, paternity and ancestry tests and thus implement privacy-enhanced online genealogy services or research projects. In the semi-honest attacker model, the protocols guarantee that no sensitive information about the involved DNA is exposed, and are resilient against common forms of measurement errors during DNA sequencing. The protocols are practical and efficient, both in terms of communication and computation complexity.
2005
CHES
2005
JOFC
2002
EPRINT
Verifiable secret sharing is an important primitive in distributed cryptography. With the growing interest in the deployment of threshold cryptosystems in practice, the traditional assumption of a synchronous network has to be reconsidered and generalized to an asynchronous model. This paper proposes the first \emph{practical} verifiable secret sharing protocol for asynchronous networks. The protocol creates a discrete logarithm-based sharing and uses only a quadratic number of messages in the number of participating servers. It yields the first asynchronous Byzantine agreement protocol in the standard model whose efficiency makes it suitable for use in practice. Proactive cryptosystems are another important application of verifiable secret sharing. The second part of this paper introduces proactive cryptosystems in asynchronous networks and presents an efficient protocol for refreshing the shares of a secret key for discrete logarithm-based sharings.
2001
CRYPTO
2001
EPRINT
Byzantine agreement requires a set of parties in a distributed system to agree on a value even if some parties are corrupted. A new protocol for Byzantine agreement in a completely asynchronous network is presented that makes use of cryptography, specifically of threshold signatures and coin-tossing protocols. These cryptographic protocols have practical and provably secure implementations in the random oracle'' model. In particular, a coin-tossing protocol based on the Diffie-Hellman problem is presented and analyzed. The resulting asynchronous Byzantine agreement protocol is both practical and theoretically nearly optimal because it tolerates the maximum number of corrupted parties, runs in constant expected time, has message and communication complexity close to the optimum, and uses a trusted dealer only in a setup phase, after which it can process a virtually unlimited number of transactions. The protocol is formulated as a transaction processing service in a cryptographic security model, which differs from the standard information-theoretic formalization and may be of independent interest.