Bitcoin Onchain Prunin g

Peter Gregory Jr. 30

th

June 2016

This document describes a concept of Bitcoin blockchain on-chain pruning. Current solutions provide only client side pruning, which is not helpful with network scaling as all new nodes still need to download full history of all trans- actions. Such an improvement allows to save roughly 95% of bandwidth, stor- age and spent CPU processing power for new nodes during synchronization.

Introduction

One of the most discuss ed and impor tant proble ms in Bitco in today is scaling. Recent impl e- mentation of Thin Blocks in Bitcoin Unlimited and planned implementation of Compact Blocks in Bitcoin Core client solves the problem of trafﬁc spikes between block propagations on Bit- coin network. This is especially important for nodes with low internet connection speeds (users runnin g nodes from home). How ev er, these soluti ons don’t solve the issue of the blockcha in size, which grows over time, as new users still need to download the whole blockchain ﬁrst in order to start operating as a node. This might take sev eral days on a low speed connectio n. For average internet connecti on speed approxima tion 1/5 of current avera ge intern et speed in the U.S. (12.6 MBs)

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is taken, which is 2.5 MBs. This ﬁgure is lower than average internet

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Akamais [state of the internet] Q3 2015 report https://www.akamai.com/us/en/multimedia/documents/state- of-the-inter net/akamai-s tate-of-the-i nternet-repor t-q3-2015.pdf