by Thaddeus Dryja (MIT’s Digital Currency Initiative)
Abstract: In the Bitcoin consensus network, all nodes come to agreement on the set of Unspent Transaction Outputs (The “UTXO” set). The size of this shared state is a scalability constraint for the network, as the size of the set expands as more users join the system, increasing resource requirements of all nodes. Decoupling the network’s state size from the storage requirements of individual machines would reduce hardware requirements of validating nodes. We introduce a hash based accumulator to locally represent the UTXO set, which is logarithmic in the size of the full set. Nodes attach and propagate inclusion proofs to the inputs of transactions, which along with the accumulator state, give all the information needed to validate a transaction. While the size of the inclusion proofs results in an increase in network traffic, these proofs can be discarded after verification, and aggregation methods can reduce their size to a manageable level of overhead. In our simulations of downloading Bitcoin’s blockchain up to early 2019 with 500MB of RAM allocated for caching, the proofs only add approximately 25% to the amount otherwise downloaded.
By Ethan Heilman (Boston Uni), Neha Narula (MIT Media Lab), Garrett Tanzer (Harvard), James Lovejoy (MIT Media Lab), Michael Colavita (Harvard), Madars Virza (MIT Media Lab), and Tadge Dryja (MIT Media Lab)
We present attacks on the cryptography formerly used in the IOTA blockchain, including under certain conditions the ability to forge signatures. We developed practical attacks on IOTA’s cryptographic hash function Curl-P-27, allowing us to quickly generate short colliding messages. These collisions work even for messages of the same length. Exploiting these weaknesses in Curl-P-27, we broke the EU-CMA security of the former IOTA Signature Scheme (ISS). Finally, we show that in a chosen-message setting we could forge signatures and multi-signatures of valid spending transactions (called bundles in IOTA).
by Jiri Chod (BU), Nikolaos Trikakis (MIT), Gerry Tsoukalas (Upenn Wharton), Henry Aspegren (MIT), and Mark Weber (MIT). Nominated for an award in the Journal of Management Science. Sept 15th, 2018
In this paper, we develop a new theory that shows signaling a firm's fundamental quality (e.g., its operational capabilities) to lenders through inventory transactions to be more efficient --- it leads to less costly operational distortions --- than signaling through loan requests, and we characterize how the efficiency gains depend on firm operational characteristics such as operating costs, market size, inventory salvage value and failure probability.
One of the earliest-seen and most persistent problems with Bitcoin has been scalability. Bitcoin takes the idea of "be your own bank" quite literally, with every computer on the bitcoin network storing every account of every user who owns money in the system. In Bitcoin, this is stored as a collection of "Unspent transaction outputs", or "utxo"s, which are somewhat unintuitive, but provide privacy and efficiency benefits over the alternative "account" based model used in traditional finance.
This paper by DCI Reserach Scientist Robleh Ali sets out a structure for a digital fiat currency system. The primary benefit of the cellular structure is that it lowers barriers to entry for payments by using trustless intermediation between cells in the system. The larger purpose of this structure is to create an open foundation for a decentralized financial system in which competition can thrive but which cannot be captured by private interests.
This paper by Christian Catalini and Joshua Gans explores how entrepreneurs can use initial coin offerings — whereby they issue crypto tokens and commit to accept only those tokens as payment for future use of a digital platform — to fund venture start-up costs.
Auditing and financial oversight are critical to proving institutions are complying with regulation. This paper presents zkLedger, the first system to protect ledger participants’ privacy and provide fast, provably correct auditing.
Smart contracts are an often touted feature of cryptographic currency systems such as Bitcoin, but they have yet to see widespread financial use. In this paper, Tadge Dryja presents a solution he calls Discrete Log Contracts.
The Web has steadily evolved into an ecosystem of large, corporate-controlled mega-platforms which intermediate speech online. In this report we explore two important ways structurally decentralized systems could help address this.
There are tremendous potential applications for blockchain technology, an innovative distributed ledger database system, within the real estate industry. This paper explores the recording of property titles.
In this draft paper by graduate researchers Keith Duffy, Pasha Goudovitch, and Pavel Fedorov, the authors explore the potential for blockchain technology to improve digital identity in the United States.