Paper 2021/289

Reactive Key-Loss Protection in Blockchains

Sam Blackshear and Konstantinos Chalkias and Panagiotis Chatzigiannis and Riyaz Faizullabhoy and Irakliy Khaburzaniya and Eleftherios Kokoris Kogias and Joshua Lind and David Wong and Tim Zakian

Abstract

We present a novel approach for blockchain asset owners to reclaim their funds in case of accidental private-key loss or transfer to a mistyped address. Our solution can be deployed upon failure or absence of proactively implemented backup mechanisms, such as secret sharing and cold storage. The main advantages against previous proposals is it does not require any prior action from users and works with both single-key and multi-sig accounts. We achieve this by a 3-phase Commit() -> Reveal() -> Claim() - or - Challenge() smart contract that enables accessing funds of addresses for which the spending key is not available. We provide an analysis of the threat and incentive models and formalize the concept of reactive KEy-Loss Protection (KELP).