Paper 2021/1282

On the Claims of Weak Block Synchronization in Bitcoin

Seungjin Baek, Hocheol Nam, Yongwoo Oh, Muoi Tran, and Min Suk Kang


Recent Bitcoin attacks [CCS'21, CCS'21, ICDCS'19] commonly exploit the phenomenon of so-called weak block synchronization in Bitcoin. The attacks use two independently-operated Bitcoin monitors — i.e., Bitnodes and a system of customized supernodes — to confirm that block propagation in Bitcoin is surprisingly slow. In particular, Bitnodes constantly reports that around 30% of nodes are 3 blocks (or more) behind the blockchain tip and the supernodes show that on average more than 60% of nodes do not receive the latest block even after waiting for 10 minutes. In this paper, we carefully re-evaluate these controversial claims with our own experiments in the live Bitcoin network and show that block propagation in Bitcoin is, in fact, fast enough (e.g., most peers we monitor receive new blocks in about 4 seconds) for its safety property. We identify several limitations and bugs of the two monitors, which have led to these inaccurate claims about the Bitcoin block synchronization. We finally ask several open-ended questions regarding the technical and ethical issues around monitoring blockchain networks.

Available format(s)
Publication info
Blockchainpeer-to-peer network
Contact author(s)
minsukk @ kaist ac kr
2021-09-24: received
Short URL
Creative Commons Attribution


      author = {Seungjin Baek and Hocheol Nam and Yongwoo Oh and Muoi Tran and Min Suk Kang},
      title = {On the Claims of Weak Block Synchronization in Bitcoin},
      howpublished = {Cryptology ePrint Archive, Paper 2021/1282},
      year = {2021},
      note = {\url{}},
      url = {}
Note: In order to protect the privacy of readers, does not use cookies or embedded third party content.