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.
“Ten years ago, a mysterious computer programmer invented a new type of money that wasn't backed by any government or kept in any bank. There were no coins or bills, just long strings of letters and numbers stored inside a network of computers that anybody could be a part of by downloading some free software over the Internet. Today that computerized currency, bitcoin, is well-known, though little understood, and bitcoin's popularity has inspired the creation of thousands of other types of digital money, known as "cryptocurrency." Over the last decade, you could have made a five million percent profit by investing in cryptocurrency. Or you could have lost everything. It has been a wild ride, and few people have experienced the highs and lows…” Cooper. A (2019, May 19) Bitcoin’s Wild Ride.
“Republican Senator Mitt Romney and Democratic Senator Chris Murphy join Christiane Amanpour from Washington D.C. to discuss their bipartisan trip to the Middle East and the growing tensions between the U.S. and Iran. Bill Weld, the only Republican challenging President Trump in the 2020 election talks about why he decided to run. Our Hari Sreenivasan talks to Neha Narula, the Director of the Digital Currency Initiative at the MIT Media Lab, about the future of cryptocurrencies.” Amanpour Podcast