Bitcoin Cash SV – 6 block chainsplit

Abstract: On 18th April 2019, the BitMEX Research Bitcoin Cash SV node experienced 2 block re-organisations. First a 3 block re-organisation, followed by a 6 block re-organisation. In this brief piece, we provide data and graphics related to the temporary chainsplit. The chainsplit appears to be caused by large blocks which took too long to propagate, rather than consensus related issues. Our analysis shows there were no double spends related to the split.

Chainsplit diagram – 18 April 2019

Source: BitMEX Research
Notes: The above image indicates there were two valid competing chains and a non-consensus split occurred at block 578,639. Our node followed the chain on the left until block 578,642, then it jumped over to the right. About an hour later, it jumped back over to the left hand side. The chain on the left continued, while the chain on the right was eventually abandoned.

Chainsplit transaction data

Number of transactions
Main chain (within 6 blocks)
Fork chain
Overlap (within 6 blocks)
Eventual double spends

Source: BitMEX Research

Based on our analysis of the transactions, all the TXIDs from the forked chain (on the right), eventually made it back into the main chain, with the obvious exception of the coinbase transactions. Therefore, it is our belief that no double spends occurred in relation to this incident.

Timestamps of the blocks related to the split – 18 April 2019

Local ClockBlock TimestampHeightHashSize (MB)Log2 Work
11:39:4711:39:19578,638 000000000000000001ccdb82b9fa923323a8d605e615047ac6c7040584eb24193.187.803278
12:04:5112:04:37578,639 0000000000000000090a43754c9c3ffb3627a929a97f3a7c37f3dee94e1fc98f8.687.803280
12:28:0112:20:36578,640 00000000000000000211d3b3414c5cb3e795e3784da599bcbb17e6929f58cc0952.287.803282
12:43:4212:29:39578,641 0000000000000000050c01ee216586175d15b683f26adcfdd9dd0be4b1742e9e42.187.803285
12:59:2712:51:40578,642 00000000000000000a7a25cea40cb57f5fce3b492030273b6f8a52f99f4bf2a876.287.803287
13:05:1812:32:39578,640 000000000000000007ad01e93696a2f93a31c35ab014d6c43597fd4fd6ba959035.587.803282
13:05:1812:33:16578,641 0000000000000000033ed7d3b1a818d82483ade2ee8c31304888932b7729f6920.187.803285
13:05:1812:41:38578,642 00000000000000000ae4a0d81d4c219139c22ba1a8a42d72b960d63a9e1579141.087.803287
13:05:1912:56:37578,643 00000000000000000590821ac2eb1d3c0e4e7edab586c16d5072ec0c77a980dc0.887.803289
13:19:3613:14:22578,644 0000000000000000001ae8668e9ab473f8862dc081f7ac65e6df9ded635d338e128.087.803291
13:21:5613:18:07578,645 0000000000000000049efe9a6e674370461c78845b98c4d045fe9cd5cb9ea634107.287.803293
14:12:5413:15:36578,643 0000000000000000016b62ec5523a1afe25672abd91fe67602ea69ee2a2b871f23.887.803289
14:12:5513:43:35578,644 000000000000000003e9d9be8a7b9fc64ef1d3494d1b0f4c11845882643a64391.387.803291
14:12:5514:01:34578,645 0000000000000000052be8613e79b33a9959535551217d7fdacc2d0c1db1e6720.087.803293
14:12:5514:06:35578,646 00000000000000000475ab103a92eb6cb1c3c666cd9af7b070e09b3a35a15d660.087.803296
14:27:0914:24:37578,647 0000000000000000062bade37849ade3e3c4dfa9289d7f5f6d203ae188e94e4f77.087.803298

Source: BitMEX Research

If one is interested, we have provided the above table which discloses all the relevant details of the blocks related to the chainsplit, including:

  • The block timestamps
  • The local clock timestamps
  • The block hashes
  • The block sizes
  • The total accumulated PoW up to each block

With the above details one can follow what occurred in relation to the chainsplit and create a timeline.

Our primary motivation for providing this information and analysis is not driven by an interest in Bitcoin Cash SV, but instead a desire to develop systems to analyse and detect these type of events on the Bitcoin network. Systems are being developed on our website,, to help detect chainsplits, caused either by poor block propagation or consensus related issues. This event on Bitcoin Cash SV is good practice for us.

As for Bitcoin Cash SV, the block sizes were particularly large during the period of the re-organisations. On the forked chain, the last two blocks were 128MB and 107MB respectively. On the main chain many of the blocks were over 50MB. Therefore, in our view, it is likely the large sizes of the blocks were the root cause of the re-organisations, as miners couldn’t propagate and verify these large blocks fast enough, before other blocks on different chains were found.

As for the implications this has on Bitcoin Cash SV, we have no comment. We will leave that to others.