SeF: A Secure Fountain Architecture for Slashing Storage Costs in Blockchains
Thursday, October 31, 2019 - 9:30am to 10:30am
Dr Swanand Kadhe, UC Berkley
The emerging field of blockchains and distributed ledgers has far-reaching applications such as healthcare, supply-chain, and Internet-of-Things. However, one of the main roadblocks in the proliferation of blockchain applications is that current blockchain designs are resource-intensive. In this talk, we will focus on blockchain storage requirements that are growing near-exponentially. We propose an architecture based on 'fountain codes', a class of erasure codes, that enables any user to 'encode' validated blocks into a small number of 'coded blocks', thereby reducing their storage costs by orders of magnitude. In particular, our proposed "Secure Fountain (SeF)" architecture can achieve a near-optimal trade-off between the storage savings per user and the 'bootstrap cost' in terms of the number of (honest) storage-constrained users that a new user needs to contact to recover the blockchain. We demonstrate that the peeling decoder admitted by fountain codes turns out to be crucial for security against adversarial users that can provide maliciously formed coded blocks. Further, the rateless property of fountain codes helps in achieving high decentralization and scalability. Our experiments demonstrate that SeF codes tuned to achieve 1000x storage savings enable users to encode the 191GB Bitcoin blockchain into 195MB on average, at the expense of 5% increase in the required bootstrap cost. This is a joint work with Jichan Chung and Kannan Ramchandran. Coffee and Monuts!