Imperial College London


Faculty of EngineeringDepartment of Computing

Professor of Applied Quantitative Analysis



+44 (0)20 7594 8331w.knottenbelt Website




E363ACE ExtensionSouth Kensington Campus






BibTex format

author = {Zamyatin, A and Stifter, N and Judmayer, A and Schindler, P and Weippl, E and Knottenbelt, W},
title = {(Short Paper) A Wild Velvet Fork Appears! Inclusive Blockchain Protocol Changes in Practice},
url = {},

RIS format (EndNote, RefMan)

AB - The loosely defined terms hard fork and soft fork have establishedthemselves as descriptors of different classes of upgrade mechanisms for the underlying consensus rules of (proof-of-work) blockchains. Recently, a novel approach termed velvet fork, which expands upon the concept of a soft fork, was outlined. Specifically, velvet forks intend to avoid the possibility of disagreement by a change of rules through rendering modifications to the protocol backward compatible and inclusive to legacy blocks.We present an overview and definitions of these different upgrade mechanisms and outline their relationships. Hereby, we expose examples where velvet forks or similar constructions are already actively employed in Bitcoin and other cryptocurrencies. Furthermore, we expand upon the concept of velvet forks by proposing possible applications and discuss potentially arising security implications.
AU - Zamyatin,A
AU - Stifter,N
AU - Judmayer,A
AU - Schindler,P
AU - Weippl,E
AU - Knottenbelt,W
TI - (Short Paper) A Wild Velvet Fork Appears! Inclusive Blockchain Protocol Changes in Practice
UR -
ER -