The continuous-time pipeline(CTP) ADC is an emerging architecture that realizes the equivalent of an anti-alias filter followed by a Nyquist-rate ADC. This work analyzes the effect of weak amplifier nonlinearities on the performance of a filter+ADC chain and compares it with that of an equivalent CTP. For a given power dissipation and noise, we show that an appropriately designed CTP is more linear when compared to a filter+ADC cascade. Our theory is verified using macro-model and transistor-level simulations.

A Fair Digital Exchange is defined as either all or none of the participants achieving a (predetermined) desirable outcome. This work addresses third party mediated systems for digital content where mutually unknown, and hence non-trusting, buyers, sellers and the mediator (third party) take part in an exchange protocol. We address the lack of guaranteed fairness, as defined above, in the existing platforms for this setting. We present TEDX, a decentralized solution for guaranteed three party fair exchange of digital goods with scalability and support for incremental deployment over the existing (non-fair) platforms. TEDX combines carefully crafted message exchanges with incentive schemes designed to deter malicious behavior. TEDX also leverages ideas from blockchain anchored state-channels to provide trusted execution while minimizing the operational overheads of blockchain. We present the design and a security analysis of TEDX to validate the claimed fairness properties. We also present the details of a prototype implementation of TEDX leveraging Hyperledger Fabric and performance evaluation of the same on a realistic testbed spanning five public cloud zones. Our results indicate that TEDX adds only a minimal overhead of 16% while being 46x faster than a naive blockchain solution, thereby demonstrating that TEDX is scalable.

The continuous-time pipelined (CTP) analog-to-digital converter is an emerging architecture that realizes the equivalent of an anti-alias filter followed by an ADC. This work compares power-noise trade-offs in CTPs with those in a filter+ADC cascade. We consider two commonly-used filter topologies, namely the Tow-Thomas and Rauch biquad structures. We show that the SNDR of an appropriately designed CTP is much higher than that achieved by a signal chain consisting of an active filter driving a Nyquist ADC. Our theory is verified using macro-model and transistor-level simulations.

We investigate the performance degradation of a continuous-time pipelined (CTP) ADC due to the input load presented by the flash sub-converter. It turns out, as we show in this work, that the flash ADC loading affects the alias rejection and the linearity of the CTP. We propose a simple technique to alleviate these problems. The theory is borne out by simulation results from a 100 MHz-bandwidth pipeline ADC designed in a 65 nm CMOS process.

Abstract Decoy Routing (DR), a promising approach to censorship circumvention, uses routers (rather than end hosts) as proxy servers. Users of censored networks, who wish to use DR, send specially crafted packets, nominally addressed to an uncensored website. Once safely out of the censored network, the packets encounter a special router (the Decoy Router) which identifies them using a secret handshake, and proxies them to their true destination (a censored site). However, DR has implementation problems: it is infeasible to reprogram routers for the complex operations required. Existing DR solutions fall back on using commodity servers as a Decoy Router. But as servers are not efficient at routing, most web applications show poor performance when accessed over DR. A further concern is that the Decoy Router has to inspect all flows in order to identify the ones that need DR. This may itself be a breach of privacy for other users (who neither require DR nor want to be monitored). In this paper, we present a novel DR system, Siege- Breaker (SB), which solves the aforementioned problems using an SDN-based architecture. Previous proposals involve a single unit which performs all major operations (inspecting all flows, identifying the DR requests and proxying them). In contrast, SB distributes the tasks for DR among three independent modules. (1) The SDN controller identifies DR requests via a covert, privacy preserving scheme, and does not need to inspect all flows. (2) The reconfigurable SDN switch intercepts packets, and forwards them to a secret proxy efficiently. (3) The secret proxy server proxies the client’s traffic to the censored site. Our modular, lightweight design achieves performance comparable to direct TCP downloads, for both in-lab setups, and Internet based tests involving commercial SDN switches.