As we greet a new decade, 2013 might feel like a very long time ago, but for a few nodes, it’s as if nothing has changed.
At least two such nodes are running the oldest version that still operates, Bitcoin Core 0.8.1.
This version was released on the 18th of March 2013, nearly 7 years ago, and is the earliest version that can still run.
The Bitcoin Core – previously Bitcoin QT – clients identify as satoshi, with 2 of them running Satoshi 0.8.1.
These are the publicly reachable nodes, so they’re “talking” to nodes, they’re validating their own transactions, and they’re participating in the running of the bitcoin network.
There are quite a few other nodes running very old versions too, but the majority of course are running the newest release.
Miners have no choice but to run the newest release if there has been a significant change, like segwit, because for miners all softforks are hard forks.
A soft fork in 2013, for example, turned into a hardfork after an incompatible block was mined. Describing the events, the then Bitcoin Core maintainer, Gavin Andresen, said:
“A block that had a larger number of total transaction inputs than previously seen was mined and broadcasted. Bitcoin 0.8 nodes were able to handle this, but some pre-0.8 Bitcoin nodes rejected it, causing an unexpected fork of the blockchain.
The pre-0.8-incompatible chain (from here on, the 0.8 chain) at that point had around 60% of the mining hash power ensuring the split did not automatically resolve (as would have occurred if the pre-0.8 chain outpaced the 0.8 chain in total work, forcing 0.8 nodes to reorganise to the pre-0.8 chain).”
That means versions older than 0.8.1 can not run today. This is however a very old version which is more kind of a museum piece than for real usage, but it is probably the oldest running node of any blockchain network.
For Bitcoin Cash, that did not even exist until August 1st 2017. While for ethereum, the oldest reachable node according to ethernodes is go v1.4.18, released on the 15th of October 2016.
That was after the DAO fork, and the v1.4.18 itself made some blockchain modifications to accounts to clean spam transactions.
Since then in ethereum there has been issuance reductions, difficulty bomb delays, and other changes, which should itself cut off previous nodes but ethernodes claims one geth v1.4.18 is running.
That node however is not in sync. The oldest version that is in sync is 1.8.22. That being the February issuance reduction earlier this year.
For bitcoin, there are plenty of old versions still running and the 0.8.1 version does seem to be sort of in sync, but those below 0.12 are of an insignificant number, 30-50 in total out of nearly 10,000.
That might be because the final alert of bitcoin nodes asked them to upgrade. When the alert key was published last year, we reported:
“The alert key functionality was removed from the protocol itself in 2016, when a final message was sent asking pre-segwit nodes running v0.12.x or older to upgrade to the segregated witnesses (segwit) client.”
Realistically, therefore, running pre-segwit clients kind of leaves you hampered, but you can do it, although with lower security.