According to Tadge Dryja, a researcher at the MIT Digital Currency Initiative, it could be possible for Bitcoin to be synchronized with just a smartphone using Utrexxo. This scaling solution is based on a idea pursued for years by developers, which seeks to streamline an aspect of the Bitcoin code, which leads to the high storage requirements.
The goal of this scaling solution is to minimize the storage that the Bitcoin network requires for operating. Currently if you wish to be a part of the Bitcoin network it is necessary to download the entire history, which at the time of writing is around 200 gigabytes.
In the written description of the project, Tadge Dryja explains that we have to differentiate between transaction history and the current state of the system.
While the transaction history is around 200GB, the current system state is around 4GB and it deals with who owns what at this point in time.It further explains that the history is not the scalability concern “as it is not used in any time-critical fashion”, but the increasing state size is.
It’s also important to note that Utreexo will not require a hard or a soft fork, It can be deployed at the wallet level, which will reduce the path to implementation significantly. It is a hash-based dynamic accumulator, which will bring the millions of UTXOs (Unspent Transaction Outputs) down to a kilobyte.
The paper further reads:
With Utreexo, the holder of funds maintains a proof that the funds exist, and provides that proof at spending time to the other nodes. These proofs are compact (under 1KB) but do represent the main downside in the utreexo model they present an additional data transmission overhead which allows much smaller state.