https://cointelegraph.com/news/blockchain-isn-t-as-decentralized-as-you-think-defense-agency-report
Among the key findings is that the following can provide room for centralization:
- old bitcoin nodes,
- unencrypted mining pools, and
- unencrypted network traffic that passes through only a limited number of ISPs.
The report also states that it is mostly just a sub-network of bitcoin nodes that are responsible for reaching consensus and communicating with miners.
It also found that older versions of the Bitcoin Core client were still running on 21% of Bitcoin nodes, despite vulnerabilities such as consensus errors.
Are you a Bitcoin holder? Watch out for this finding!!
