Clearing Up Misconceptions About Full Nodes

This number comes from sites like this and it measured by trying to connect to every nodes on their open ports.

Problem is, not all nodes actually have open ports that can be probed. Either because they are behind firewalls or because their users have configured them to not listen for connections.

Nobody knows exactly how many full nodes there are, since many people don't know how to forward ports behind a firewall, and bandwidth can be costly, its quite likely that the number of nodes with closed ports is at least another several thousand.

Nodes with open ports are able to upload blocks to new full nodes. In all other ways they are the same as nodes with closed ports. But because open-port-nodes can be measured and closed-port-nodes cannot, some members of the bitcoin community have been mistaken into believing that open-port-nodes represent the full count.

Nodes with open ports are useful to the bitcoin network because they help bootstrap new nodes by uploading historical blocks -- they are a measure of the number of redundant copies of the blockchain available for synchronizing with. There has been no shortage of bandwidth capacity for simply syncing wallets from the available nodes, and if there were, bandwidth might be added by renting cloud servers.

Trust, security, and privacy are what matters right now. Full nodes are able to check that all of bitcoin's rules are being followed. Rules like following the inflation schedule, no spending the same coin twice, no spending of coins that don't belong to the holder of the private key and all the other rules required to make bitcoin work (e.g. difficulty)

Full nodes are required to make bitcoin trustless. No longer do you have to trust a financial institution like a bank or paypal, you can simply run software on your own computer. To put simply, the only node that matters is the one you use.

It is very much in the individual bitcoin's users rational self interest to run a full node and use it as their wallet.

Trustless

An example of a lightweight client happily accepting a fake transaction. If the attacker had some hashpower then this transaction could be made to have confirmations too.

Running a full node as your wallet is the only way to know for sure that none of bitcoin's rules have been broken. Rules like no coins were spent not belonging to the owner, that no coins were spent twice, that no inflation happens outside of the schedule and that all the rules needed to make the system work are followed (e.g. Difficulty.) All other kinds of wallet involve trusting a third party server.

If bitcoin is digital gold, then a full node wallet is your own personal goldsmith who checks for you that received payments are genuine. You wouldn't accept a cash banknote or gold coin without checking it is genuine, the same applies for bitcoin.

To get the benefits of running a full node, you must use it as your wallet, preferably on hardware you control.

Most people who do this do not use a full node as their wallet. Unfortunately because Bitcoin has a similar name to Bittorrent, some people believe that upload capacity is the most important thing for a healthy network. As I've explained above: bandwidth and connections are not a problem today; trust, security and privacy are.

This was common advice in 2012, but since then the full node software has vastly improved in terms of user experience.

If you cannot spare the disk space to store the blockchain, you can enable pruning. Altogether this should require less than 900MB of hard disk space.

If you cannot spare the bandwidth to upload blocks to other nodes, there are number of options to reduce or eliminate the bandwidth requirement. These include limiting connections, bandwidth targeting and disabling listening. There is also the option -blocksonly, where the node will not download unconfirmed transaction and only download new blocks. This more than halves the bandwidth usage at the expense of not seeing unconfirmed transactions.

Synchronizing the blockchain for a new node has improved since 2012 too. Features like and libsecp256k1 have greatly improved the initial synchronization time.

It can be further improved by setting -dbcache=3000 which keeps more of the UTXO set in memory. It reduces the amount of time reading from disk and therefore speeds up synchronization. Tests showed that the entire blockchain can now be synchronized in less than **3 and a half hours** (Note that you'll need Bitcoin Core 0.12 or later to get all these efficiency improvements) Another example with 2h 25m

I think every moderate user of bitcoin would benefit by running a full node and using it as their wallet. There are several ways to do this.

• Run a bitcoin-qt full node.

• Use wallet software that is backed by a full node (e.g. Armory, JoinMarket

• Use a lightweight wallet that connects only to your full node (e.g. GreenAddress connecting only to your node running at home, Electrum connecting only to your own Electrum server)
  • Electrum Personal Server is designed specifically for this use case.

So what are you waiting for? The benefits are many, the downsides are not that bad. The more people do this, the more robust and healthy the bitcoin ecosystem is.

Measuring Decentralization - Truthcoin

Pieter Wuille's explaination of full node trustlessness

bitcoin.org's article on validation

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