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75% of Bitcoin SV [BSV] hashrate is contained in 4 nodes, double-spending 0-conf transactions possible, discovers programmer

Anirudh VK



75% of Bitcoin SV [BSV] hashrate is contained in 4 nodes, double-spending 0-conf transactions possible, discovers programmer
Source: Unsplash

Bitcoin Satoshi’s Vision [BSV] has been in the news recently due to its inflated price growth over the past week. However, a programmer and computer security researcher is known as Reizu recently found that, among other things, it is possible to double spend a zero-confirmation transaction on the BSV chain.

He also discovered that the hashrate on the network is also highly concentrated, with just 4 nodes controlling over 75% of the hashrate, out of the 450 nodes on the network. He begins by saying that double spending a 0-conf transaction is possible, but restricted by multiple real-world limitations. These include the fact that the propagation of transactions is very fast on the Bitcoin network, and that miners follow the “first seen safe” rule.

Moreover, whenever fees of greater than 1 satoshi/byte are used, the transaction is considered safe. In case of double-spending actually occurring, it is easy to detect it by connecting to several different nodes and waiting for 5 seconds, as that would effectively show if transactions have the same output.

Reizu stated that the main reason he picked Bitcoin SV is that the community believes that 0-conf transactions are safe, and said that he wanted to see whether it was possible to send a transaction to one node and another transaction with the same input to another node. He discovered that he indeed could, and presented a short tutorial doing so, using a tool known as izubitcoin.

The tool has some features that enable this, such as using parallelization to connect to each node on the network and connecting to the Bitcoin protocol natively. He explained:

“Once connected to the remote nodes (after a few seconds) I send a signal to the processes. Upon receipt, each thread sends the transaction to their node and disconnects. In this way the synchronization is very effective.”

The condition is exploited on the BSV network with a success rate between 90% and 97%, with a simultaneous connection to all the nodes on the network allowing for a precise control over the distribution of the transactions.

When trying to discover whether double spending was possible by sending the first transaction to a set of non-mining nodes and the second to a minority of mining nodes, he saw that the mined transactions were always sent to the same nodes. This confirms that the mining of the BSV chain is very centralized. More specifically:

“34% of the hashrate is only 1 node. 59% of the hashrate are 2 nodes. 68% of the hashrate are 3 nodes. 75% of the hashrate are 4 nodes.”

The programmer further said that he has double-spent many transactions on the BSV network, with a 90% success rate if the second transactions are sent to 6 nodes and a 100% success rate if sent to 20 nodes. He further found that the difficulty of double-spending is proportional to the number of nodes on the network and that doing it is “practically free”, as one needs only an internet connection and a mid-range or high-end router.

Moreover, this method works even if all miners are honest, which opens up the BSV network to a host of double spend attacks. Even as the network is presenting itself as one of the biggest payment networks of the next decade, this exploit must be fixed before it can compete for the position.

Double-spending 0-conf POP! BSV from reizu on Vimeo.

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Anirudh VK is a full-time journalist at AMBCrypto. He has a passion for writing and interest towards the future of blockchain technology and cryptocurrencies. He does not own any cryptocurrencies currently.


Bitcoin SV [BSV] gets hit with another reorg as multiple blocks get orphaned, including a 128 MB block

Akash Anand



Bitcoin SV [BSV] gets hit with another reorg as multiple blocks get orphaned, including a 128 MB block
Source: Pixabay

Bitcoin SV [BSV] and its proponents have been making headlines over the past couple of weeks, either due to developments or because of comments made by its major proponents, Craig Wright, the chief scientist at nChain, and Calvin Ayre.

The network was also hit with several members of the cryptocurrency community alleging that the cryptocurrency itself is a sham without any use cases, as evidenced by its delisting on several popular cryptocurrency exchanges like Binance, Kraken and Shapeshift.

The latest news added salt to BSV’s wounds after it was revealed that the network went through another blockchain reorganization on a 128 MB block. This fact was pointed out by Nikita Zhavoronkov, the lead developer of Blockchair, who had tweeted:

“Whoops! $BSV has experienced yet another reorg, this time 6 (six!) consecutive blocks were orphaned (#578640–578645), this chain included a 128 MB block #578644 🤦‍♂️ The network was basically stuck for 1.5 hours, and this shows that even 6 confirmations are not enough.”

Orphaned blocks are valid blocks which are not part of the main chain. There are ways that they can occur naturally when two miners produce blocks at similar times or they can be a result of an attacker with enough hashing power using it for nefarious activities like reversing transactions.

A major reason why this reorg event made news was that a major 128 MB block was stuck in transaction, something that was not supposed to occur according to the initial claims made by the SV camp. Supporters of the cryptocurrency, however, have stated that despite being slower than promised, the transactions on the block settled faster than that on a Bitcoin Core block.

One supporter of BSV, mboyd1, tweeted:

“Orphaned blocks are a feature, not a bug”

To this tweet, Zyo, another cryptocurrency enthusiast replied:

“yes, but orphaning 6 blocks in a row is not good, that means that 6 confirmations is not safe. It’s a bug because the 100+ MB take way too long to propagate and validate. There is a reason why BCH doesn’t have [yet] 100+ MB blocks.”

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