Design and analysis of the radiator structure for space power systems

The design, analysis, fabrication, and development of the 5-kWe radiator structure are shown. Thermal performance, meteoroid protection, structural capability during launch, development testing and space operation, material evaluation, and the configuration selection are described. The fin-tube development program depends on the relative values of the thermal coefficients of expansion. The initial selection of aluminum fins and Type 316 stainless-steel tubes was based on previous experience; however, the large differential in their expansion rates showed that an alternate, more compatible, combination was needed. Copper, stainless-steel-clad copper, boron-impregnated aluminum, and an independent radiator with a titanium structure were all considered as alternate materials. The final selection was Lockalloy fins with Type 304 stainless-steel D tubes

Secure Systems from Insecure Components

In many computer systems today, an attacker that compromises just one system component can steal many users’ data. Unfortunately, past experience shows that attackers are very effective at compromising system components, whether by exploiting some software vulnerability, compromising hardware, or launching a phishing attack.In this thesis, we show how to build systems that provide strong security and privacy properties even if the individual components are insecure. This way, even if an attacker compromises any single component in the system, it cannot compromise user security and privacy. While this property is possible to achieve in theory using general-purpose cryptographic techniques, the challenge is to instantiate it efficiently in practice. The key idea is to co-design the system with the cryptography to reduce costs.We examined two core aspects of this problem: hiding queries and securing accounts. Users who store their data encrypted at servers still need to query their data. We built systems that provide both strong privacy guarantees and good concrete efficiency for keyword search (DORY), time-series analytics queries (Waldo), and object stores (Snoopy). Users also need to protect their accounts in the event of client device loss or compromise, but also in the event of service provider compromise. We built an encrypted backup system that relies on secure hardware without fully trusting it (SafetyPin) and a service that records every authentication without learning private information (larch).The Signal end-to-end encrypted messaging application uses some of the techniques in Snoopy to scale its private contact discovery service, which privately matches user contacts to Signal users

Improved Portable Back Pain Relief Device with User Interface

The objective of this project is to design and create a massage system that is user interactive, portable, safe, efficient, and comfortable. The system should allow for user feedback from an outside peripheral such as a phone to be able to modify the system. Some challenges facing the implementation of such a system include: ensuring the product can withstand substantial force without breaking or malfunctioning while simultaneously being light enough for a consumer to carry without difficulty, engineering the massage heads to be able to move in multiple different motion types, creating the software that can control the device, and implementing a way for the user to easily power the system

Accountable authentication with privacy protection: The Larch system for universal login

Credential compromise is hard to detect and hard to mitigate. To address this problem, we present larch, an accountable authentication framework with strong security and privacy properties. Larch protects user privacy while ensuring that the larch log server correctly records every authentication. Specifically, an attacker who compromises a user's device cannot authenticate without creating evidence in the log, and the log cannot learn which web service (relying party) the user is authenticating to. To enable fast adoption, larch is backwards-compatible with relying parties that support FIDO2, TOTP, and password-based login. Furthermore, larch does not degrade the security and privacy a user already expects: the log server cannot authenticate on behalf of a user, and larch does not allow relying parties to link a user across accounts. We implement larch for FIDO2, TOTP, and password-based login. Given a client with four cores and a log server with eight cores, an authentication with larch takes 150ms for FIDO2, 91ms for TOTP, and 74ms for passwords (excluding preprocessing, which takes 1.23s for TOTP).Comment: This is an extended version of a paper appearing at OSDI 202

SNAP 2 POWER CONVERSION SYSTEM. ROTATIONAL SPEED CONTROL. Topical Report No. 18

The rotational speed control for the SNAP 2 power conversion system employs the concept of controlling speed by electrically loading the alternator. Speed is controlled in this manner to plus or minus 1% of nominal. This report covers work performed from March 1, 1960 to July 1, 1961. (auth

Reducing Participation Costs via Incremental Verification for Ledger Systems

Ledger systems are applications run on peer-to-peer networks that provide strong integrity guarantees. However, these systems often have high participation costs. For a server to join this network, the bandwidth and computation costs grow linearly with the number of state transitions processed; for a client to interact with a ledger system, it must either maintain the entire ledger system state like a server or trust a server to correctly provide such information. In practice, these substantial costs centralize trust in the hands of the relatively few parties with the resources to maintain the entire ledger system state. The notion of *incrementally verifiable computation*, introduced by Valiant (TCC \u2708), has the potential to significantly reduce such participation costs. While prior works have studied incremental verification for basic payment systems, the study of incremental verification for a general class of ledger systems remains in its infancy. In this paper we initiate a systematic study of incremental verification for ledger systems, including its foundations, implementation, and empirical evaluation. We formulate a cryptographic primitive providing the functionality and security for this setting, and then demonstrate how it captures applications with privacy and user-defined computations. We build a system that enables incremental verification, for applications such as privacy-preserving payments, with universal (application-independent) setup. Finally, we show that incremental verification can reduce participation costs by orders of magnitude, for a bare-bones version of Bitcoin

SNAP I POWER CONVERSION SYSTEM CONTROL DEVELOPMENT. Period covered: February 1, 1957 to June 30, 1959

Development of the control elements for the SNAP 1 power conversion system is described. A description of test and prototype hardware and performance data are included. The control package in its final design is a combination of regulator and speed-sensitive feedback which provides satisfactory steady-state operation and serves as a mechanism correction for system disturbances. (J.R.D.

Private Web Search with Tiptoe

Tiptoe is a private web search engine that allows clients to search over hundreds of millions of documents, while revealing no information about their search query to the search engine’s servers. Tiptoe’s privacy guarantee is based on cryptography alone; it does not require hardware enclaves or non-colluding servers. Tiptoe uses semantic embeddings to reduce the problem of private full-text search to private nearest-neighbor search. Then, Tiptoe implements private nearest-neighbor search with a new, high-throughput protocol based on linearly homomorphic encryption. Running on a 45-server cluster, Tiptoe can privately search over 360 million web pages with 145 core-seconds of server compute, 56.9 MiB of client-server communication (74% of which occurs before the client enters its search query), and 2.7 seconds of end-to-end latency. Tiptoe’s search works best on conceptual queries (“knee pain”) and less well on exact string matches (“123 Main Street, New York”). On the MS MARCO search-quality benchmark, Tiptoe ranks the best-matching result in position 7.7 on average. This is worse than a state-of-the-art, non-private neural search algorithm (average rank: 2.3), but is close to the classical tf-idf algorithm (average rank: 6.7). Finally, Tiptoe is extensible: it also supports private text-to-image search and, with minor modifications, it can search over audio, code, and more