Monero's March 23, 2016 Hard Fork: What You Need to Know (Updated)
Monero's first scheduled protocol upgrade lands this week. Here is what changes, what you need to do, and what you can safely ignore.
What is happening
Around March 23, 2016 the Monero network will pass block 1,009,827 and switch to version 2 of the consensus rules. Unlike the emergency fixes of 2014, this one has been on the roadmap for months: the rules were merged into the codebase last year, the block height was fixed well in advance, and the network has been signalling its readiness for weeks. It is the first use of Monero's policy of regular, pre-announced hard forks, which the core team intends to repeat roughly every six months so that improvements do not sit unmerged for years.
What changes at the fork
- Block time doubles from 60 to 120 seconds. The one-minute target produced a lot of orphaned blocks and made propagation harder for nodes on slow connections. Two minutes is still fast by cryptocurrency standards.
- Block reward doubles to match. Because blocks arrive half as often, the per-block reward is doubled so the overall emission curve is unchanged. Nothing about the total supply or the tail emission moves.
- Minimum ring size becomes 3 (a "mixin" of 2). Transactions with zero or one decoy are no longer accepted. This closes off the easiest way to accidentally reveal which output you are spending, and it improves privacy for everyone else, since your outputs stop being used as decoys next to obviously-real spends.
- Unlock times and transaction sanity limits are tightened to prevent a few silly edge cases. Ordinary users will never notice these.
What you need to do
- Run 0.9.2 or later. The current release, 0.9.2 "Hydrogen Helix", contains the new rules and will switch automatically at the fork height. Older nodes will follow the old rules and end up on a dead chain.
- Check your wallet's default mixin. The GUI-less
simplewalletdefaults to a mixin of 4, which is fine. If you have scriptedtransfercommands withmixin 0or1, they will be rejected after the fork. - If you use a pool or exchange, do nothing. Every major pool and exchange has confirmed they are upgraded. Expect a short pause in deposits and withdrawals around the fork height while operators watch the chain settle.
- Do not panic-sell your "old" coins. There is no new coin, no snapshot and no airdrop. Your Monero is your Monero on both sides of the fork.
What about the emission?
This question comes up every time. Doubling the block time and doubling the block reward cancel out: the network still emits the same amount of XMR per day as before, and the curve toward the 0.6 XMR/block tail emission is unchanged. The only visible difference is that your mining payouts arrive in larger, less frequent chunks.
Update — March 23
The fork has passed without incident. Block 1,009,827 was found late on the 22nd UTC, the first v2 blocks followed with a two-minute target, and the major pools and exchanges resumed normal operation within the hour. A small number of miners who had not upgraded briefly produced blocks on the old rules; those were orphaned and the hashrate has since moved over. If you are still seeing your daemon report a height well below the explorers, you are on an old version — upgrade and let it resync.