Mastering Bitcoin, 3rd Edition

Appendix B. Errata to the Bitcoin Whitepaper

This appendix contains a description of known problems in Satoshi Nakamoto’s paper, “Bitcoin: A Peer-to-Peer Electronic Cash System,” as well as notes on terminology changes and how Bitcoin’s implementation differs from that described in the paper.

This document was originally published by a coauthor of this book in 2016; it is reproduced here with updates. The names of sections in this errata correspond to the names of the sections in Nakamoto’s original paper.

Abstract

“The longest chain not only serves as proof of the sequence of events witnessed, but proof that it came from the largest pool of CPU power.”

• Implementation detail: If each link in the chain (called “blocks” in Bitcoin) was built using the same amount of proof of work (PoW), the longest chain would be the one backed by the largest pool of computational power. However, Bitcoin was implemented in such a way that the amount of PoW can vary between blocks, so it became important not to check for the “the longest chain” but rather “the chain demonstrating the most PoW”; this is often shortened to “most-work chain.”

  The change from checking for the longest chain to checking for the most-work chain occurred in July 2010, long after Bitcoin’s initial release:

  -    if (pindexNew->nHeight > nBestHeight)
  +    if (pindexNew->bnChainWork > bnBestChainWork)

• Terminology change: General CPUs were used to generate the PoW for the earliest Bitcoin blocks, but PoW generation today is ...