Raphael M. Reischuk

Verifiable delegation of computation on outsourced data

We address the problem in which a client stores a large amount of data with an untrusted server in such a way that, at any moment, the client can ask the server to compute a function on some portion of its outsourced data. In this scenario, the client must be able to efficiently verify the correctness of the result despite no longer knowing the inputs of the delegated computation, it must be able to keep adding elements to its remote storage, and it does not have to fix in advance (i.e., at data outsourcing time) the functions that it will delegate. Even more ambitiously, clients should be able to verify in time independent of the input-size -- a very appealing property for computations over huge amounts of data. In this work we propose novel cryptographic techniques that solve the above problem for the class of computations of quadratic polynomials over a large number of variables. This class covers a wide range of significant arithmetic computations -- notably, many important statistics. To confirm the efficiency of our solution, we show encouraging performance results, e.g., correctness proofs have size below 1 kB and are verifiable by clients in less than 10 milliseconds.

SIBRA: Scalable Internet Bandwidth Reservation Architecture

This paper proposes a Scalable Internet Bandwidth Reservation Architecture (SIBRA) as a new approach against DDoS attacks, which, until now, continue to be a menace on todays Internet. SIBRA provides scalable inter-domain resource allocations and botnet-size independence, an important property to realize why previous defense approaches are insufficient. Botnet-size independence enables two end hosts to set up communication regardless of the size of distributed botnets in any Autonomous System in the Internet. SIBRA thus ends the arms race between DDoS attackers and defenders. Furthermore, SIBRA is based on purely stateless operations for reservation renewal, flow monitoring, and policing, resulting in highly efficient router operation, which is demonstrated with a full implementation. Finally, SIBRA supports Dynamic Interdomain Leased Lines (DILLs), offering new business opportunities for ISPs.

SAFE extensibility of data-driven web applications

This paper presents a novel method for enabling fast development and easy customization of interactive data-intensive web applications. Our approach is based on a high-level hierarchical programming model that results in both a very clean semantics of the application while at the same time creating well-defined interfaces for customization of application components. A prototypical implementation of a conference management system shows the efficacy of our approach.

Maintaining state in propagation solvers

Constraint propagation solvers interleave propagation, removing impossible values from variable domains, with search. The solver state is modified during propagation. But search requires the solver to return to a previous state. Hence a propagation solver must determine how to maintain state during propagation and forward and backward search. This paper sets out the possible ways in which a propagation solver can choose to maintain state, and the restrictions that such choices place on the resulting system. Experiments illustrate the result of various choices for the three principle state components of a solver: variables, propagators, and dependencies between them. This paper also provides the first realistic comparison of trailing versus copying for state restoration.

Authentication Challenges in a Global Environment

In this article, we address the problem of scaling authentication for naming, routing, and end-entity (EE) certification to a global environment in which authentication policies and users’ sets of trust roots vary widely. The current mechanisms for authenticating names (DNSSEC), routes (BGPSEC), and EE certificates (TLS) do not support a coexistence of authentication policies, affect the entire Internet when compromised, cannot update trust root information efficiently, and do not provide users with the ability to make flexible trust decisions. We propose the Scalable Authentication Infrastructure for Next-generation Trust (SAINT), which partitions the Internet into groups with common, local trust roots and isolates the effects of a compromised trust root. SAINT requires groups with direct routing connections to cross-sign each other for authentication purposes, allowing diverse authentication policies while keeping all entities’ authentication information globally discoverable. SAINT makes trust root management a central part of the network architecture, enabling trust root updates within seconds and allowing users to make flexible trust decisions. SAINT operates without a significant performance penalty and can be deployed alongside existing infrastructures.

The SCION internet architecture

Adhering to the end-to-end principle even more than the current Internet yields highly available point-to-point communication.

G2C: cryptographic protocols from goal-driven specifications

We present G2C, a goal-driven specification language for distributed applications. This language offers support for the declarative specification of functionality goals and security properties. The former comprise the parties, their inputs, and the goal of the communication protocol. The latter comprise secrecy, access control, and anonymity requirements. A key feature of our language is that it abstracts away from how the intended functionality is achieved, but instead lets the system designer concentrate on which functional features and security properties should be achieved. Our framework provides a compilation method for transforming G2C specifications into symbolic cryptographic protocols, which are shown to be optimal. We provide a technique to automatically verify the correctness and security of these protocols using ProVerif, a state-of-the-art automated theorem-prover for cryptographic protocols. We have implemented a G2C compiler to demonstrate the feasibility of our approach.

IKP: Turning a PKI Around with Decentralized Automated Incentives

Despite a great deal of work to improve the TLS PKI, CA misbehavior continues to occur, resulting in unauthorized certificates that can be used to mount man-in-the-middle attacks against HTTPS sites. CAs lack the incentives to invest in higher security, and the manual effort required to report a rogue certificate deters many from contributing to the security of the TLS PKI. In this paper, we present IKP, a platform that automates responses to unauthorized certificates and provides incentives for CAs to behave correctly and for others to report potentially unauthorized certificates. Domains in IKP specify criteria for their certificates, and CAs specify reactions such as financial penalties that execute in case of unauthorized certificate issuance. By leveraging smart contracts and blockchain-based consensus, we can decentralize IKP while still providing automated incentives. We describe a theoretical model for payment flows and implement IKP in Ethereum to show that decentralizing and automating PKIs with financial incentives is both economically sound and technically viable.

SCION: A Secure Internet Architecture

This book describes the essential components of the SCION secure Internet architecture, the first architecture designed foremost for strong security and high availability. Among its core features, SCION also provides route control, explicit trust information, multipath communication, scalable quality-of-service guarantees, and efficient forwarding. The book includes functional specifications of the network elements, communication protocols among these elements, data structures, and configuration files. In particular, the book offers a specification of a working prototype. The authors provide a comprehensive description of the main design features for achieving a secure Internet architecture. They facilitate the reader throughout, structuring the book so that the technical detail gradually increases, and supporting the text with a glossary, an index, a list of abbreviations, answers to frequently asked questions, and special highlighting for examples and for sections that explain important research, engineering, and deployment features. The book is suitable for researchers, practitioners, and graduate students who are interested in network security.

The SCION Architecture

This chapter provides an overview of SCION. The goals to be met by a secure Internet architecture were described in the previous chapter, but to recapitulate briefly, our main aim is to design a network architecture that offers highly available and efficient point-to-point packet delivery, even if some of the network operators and devices are actively malicious. The following chapters describe the SCION architecture in increasing detail.