IA-CCF: Individual accountability for permissioned ledgers

Permissioned ledger systems allow a consortium of members that do not trust one another to execute transactions safely on a set of replicas. Such systems typically use Byzantine fault tolerance (BFT) protocols to distribute trust, which only ensures safety when fewer than 1/3 of the replicas misbehave. Providing guarantees beyond this threshold is a challenge: current systems assume that the ledger is corrupt and fail to identify misbehaving replicas or hold the members that operate them accountable—instead all members share the blame. We describe IA-CCF, a new permissioned ledger system that provides individual accountability. It can assign blame to the individual members that operate misbehaving replicas regardless of the number of misbehaving replicas or members. IA-CCF achieves this by signing and logging BFT protocol messages in the ledger, and by using Merkle trees to provide clients with succinct, universally-verifiable receipts as evidence of successful transaction execution. Anyone can audit the ledger against a set of receipts to discover inconsistencies and identify replicas that signed contradictory statements. IACCF also supports changes to consortium membership and replicas by tracking signing keys using a sub-ledger of governance transactions. IA-CCF provides strong disincentives to misbehavior with low overhead: it executes 47,000 tx/s while providing clients with receipts in two network round trips

Confidential Consortium Framework: Secure Multiparty Applications with Confidentiality, Integrity, and High Availability

Confidentiality, integrity protection, and high availability, abbreviated to CIA, are essential properties for trustworthy data systems. The rise of cloud computing and the growing demand for multiparty applications however means that building modern CIA systems is more challenging than ever. In response, we present the Confidential Consortium Framework (CCF), a general-purpose foundation for developing secure stateful CIA applications. CCF combines centralized compute with decentralized trust, supporting deployment on untrusted cloud infrastructure and transparent governance by mutually untrusted parties. CCF leverages hardware-based trusted execution environments for remotely verifiable confidentiality and code integrity. This is coupled with state machine replication backed by an auditable immutable ledger for data integrity and high availability. CCF enables each service to bring its own application logic, custom multiparty governance model, and deployment scenario, decoupling the operators of nodes from the consortium that governs them. CCF is open-source and available now at https://github.com/microsoft/CCF.Comment: 16 pages, 9 figures. To appear in the Proceedings of the VLDB Endowment, Volume 1

Abstract High-Performance Memory-Based Web Servers: Kernel and User-Space Performance

Web server performance has steadily improved since the inception of the World Wide Web. We observe performance gains of two orders of magnitude between the original process-based Web servers and today’s threaded Web servers. Commercial and academic Web servers achieved much of these gains using new or improved event-notification mechanisms and techniques to eliminate reading and copying data, both of which required new operating system primitives. More recently, experimental and production Web servers began integrating HTTP processing in the TCP/IP stack and providing zero copy access to a kernel-managed cache. These kernelmode Web servers improved upon newer user-mode Web servers by a factor of two to six. This paper analyzes the significant performance gap between the newer user-mode and kernel-mode Web servers on Linux and Windows 2000. Several user-mode and kernel-mode Web servers are compared in three areas: data movement, event notification, and communication code path. To establish a user-mode baseline, the paper measures the performance of highly optimized Web servers. The paper positions these user-mode implementations with those from related research projects. In particular, the “Adaptive Fast Path Architecture ” (AFPA) is described and then used to implement kernel-mode Web servers on Linux and Windows 2000. AFPA is a platform for implementing kernel-mode network servers on production operating systems without kernel modifications. AFPA runs on Linux, Windows 2000, AIX, and S/390. The results show that kernel-mode performance greatl

Sampling and haplotype locations.

<p>Map showing location and haplotype designations of each clade according to the phylogenetic tree. Circles represent the Northern clade, diamonds represent the VIC/TAS/NSW clade, crosses represent the Sunshine Coast clade, squares represent both NSW 1 and NSW 2 clades, and stars represent cities. The open shapes represent haplotypes from Zenger <i>et al</i>. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0128160#pone.0128160.ref023" target="_blank">23</a>] and solid black coloured shapes represent new haplotypes sampled in this paper. Inset is the Sunshine Coast region; shading in inset indicates contemporary temperate rainforest.</p