Verifiable ASICs

A manufacturer of custom hardware (ASICs) can undermine the intended execution of that hardware; high-assurance execution thus requires controlling the manufacturing chain. However, a trusted platform might be orders of magnitude worse in performance or price than an advanced, untrusted platform. This paper initiates exploration of an alternative: using verifiable computation (VC), an untrusted ASIC computes proofs of correct execution, which are verified by a trusted processor or ASIC. In contrast to the usual VC setup, here the prover and verifier together must impose less overhead than the alternative of executing directly on the trusted platform. We instantiate this approach by designing and implementing physically realizable, area-efficient, high throughput ASICs (for a prover and verifier), in fully synthesizable Verilog. The system, called Zebra, is based on the CMT and Allspice interactive proof protocols, and required new observations about CMT, careful hardware design, and attention to architectural challenges. For a class of real computations, Zebra meets or exceeds the performance of executing directly on the trusted platform

Proof of Luck: an Efficient Blockchain Consensus Protocol

In the paper, we present designs for multiple blockchain consensus primitives and a novel blockchain system, all based on the use of trusted execution environments (TEEs), such as Intel SGX-enabled CPUs. First, we show how using TEEs for existing proof of work schemes can make mining equitably distributed by preventing the use of ASICs. Next, we extend the design with proof of time and proof of ownership consensus primitives to make mining energy- and time-efficient. Further improving on these designs, we present a blockchain using a proof of luck consensus protocol. Our proof of luck blockchain uses a TEE platform's random number generation to choose a consensus leader, which offers low-latency transaction validation, deterministic confirmation time, negligible energy consumption, and equitably distributed mining. Lastly, we discuss a potential protection against up to a constant number of compromised TEEs.Comment: SysTEX '16, December 12-16, 2016, Trento, Ital

Implementation Study of Two Verifiable Delay Functions

Proof of Work is a prevalent mechanism to prove investment of time in blockchain projects. However, the use of massive parallelism and specialized hardware gives an unfair advantage to a small portion of nodes and raises environmental and economical concerns. In this paper, we provide an implementation study of two Verifiable Delay Functions, a new cryptographic primitive achieving Proof of Work goals in an unparallelizable way. We provide simulation results and an optimization based on a multiexponentiation algorithm