2 P2P or Not 2 P2P?

In the hope of stimulating discussion, we present a heuristic decision tree that designers can use to judge the likely suitability of a P2P architecture for their applications. It is based on the characteristics of a wide range of P2P systems from the literature, both proposed and deployed.Comment: 6 pages, 1 figur

Towards Tamper-Evident Storage on Patterned Media

We propose a tamper-evident storage system based on probe storage with a patterned magnetic medium. This medium supports normal read/write operations by out-of-plane magnetisation of individual magnetic dots. We report on measurements showing that in principle the medium also supports a separate class of write-once operation that destroys the out-of-plane magnetisation property of the dots irreversibly by precise local heating. We discuss the main issues of designing a tamper-evident storage device and file system using the properties of the medium

MoPS: A Modular Protection Scheme for Long-Term Storage

Current trends in technology, such as cloud computing, allow outsourcing the storage, backup, and archiving of data. This provides efficiency and flexibility, but also poses new risks for data security. It in particular became crucial to develop protection schemes that ensure security even in the long-term, i.e. beyond the lifetime of keys, certificates, and cryptographic primitives. However, all current solutions fail to provide optimal performance for different application scenarios. Thus, in this work, we present MoPS, a modular protection scheme to ensure authenticity and integrity for data stored over long periods of time. MoPS does not come with any requirements regarding the storage architecture and can therefore be used together with existing archiving or storage systems. It supports a set of techniques which can be plugged together, combined, and migrated in order to create customized solutions that fulfill the requirements of different application scenarios in the best possible way. As a proof of concept we implemented MoPS and provide performance measurements. Furthermore, our implementation provides additional features, such as guidance for non-expert users and export functionalities for external verifiers.Comment: Original Publication (in the same form): ASIACCS 201

Securing Logs in Operation-based Collaborative Editing

The Twelfth International Workshop on Collaborative Editing Systems, CSCW'12International audienceIn recent years collaborative editing systems such as wikis, GoogleDocs and version control systems became very popular. In order to improve reliability, fault-tolerance and availability shared data is replicated in these systems. User misbehaviors can make the system inconsistent or bring corrupted updates to replicated data. Solutions to secure data history of state-based replication exist, however they are hardly applied to operation-based replication. In this paper we propose an approach to secure log in operation-based optimistic replication system. authenticators based on hash values and digital signatures are generated each time a site shares or receives new updates on replicas. authenticators secure logs with security properties of integrity and authenticity. We present in detail algorithms to construct and verify authenticators and we analyse their complexities

Embedding a Deterministic BFT Protocol in a Block DAG

This work formalizes the structure and protocols underlying recent distributed systems leveraging block DAGs, which are essentially encoding Lamport's happened-before relations between blocks, as their core network primitives. We then present an embedding of any deterministic Byzantine fault tolerant protocol ℘ to employ a block DAG for interpreting interactions between servers. Our main theorem proves that this embedding maintains all safety and liveness properties of ℘. Technically, our theorem is based on the insight that a block DAG merely acts as an efficient reliable point-to-point channel between instances of ℘ while also using ℘ for efficient message compression

VoteBox Nano: A smaller, stronger FPGA-based voting machine

This thesis describes a minimal implementation of a cryptographically secure direct recording electronic (DRE) voting system, built with a low-cost Xilinx FPGA board. Our system, called VoteBox Nano, follows the same design principles as the VoteBox, a full-featured electronic voting system. The votes are encrypted using El-gamal homomorphic encryption and the correctness of the system can be challenged by real voters during an ongoing election. In order to fit within the limits of a minimal FPGA, VoteBox Nano eliminates VoteBox's sophisticated network replication mechanism and full-color bitmap graphics system. In return, VoteBox Nano runs without any operating or language runtime system and interacts with the voter using simple character graphics, radically shrinking the implementation complexity. VoteBox Nano also integrates a true random number generator (TRNG), providing improved security. In order to deter hardware tampering, we used FPGA's native JTAG interface coupled with TRNG. At boot-time, the proper FPGA configuration displays a random number on the built-in display. Any interaction with the JTAG interface will change this random number, allowing the poll workers to detect election-day tampering, simply by observing whether the number has changed