Proof of space and time

Chia's consensus answers the same question as Bitcoin's mining, who gets to add the next block?, but with a lottery you enter by storing data rather than by computing hashes as fast as possible.

Proof of space

A farmer fills disks with plots: large files of precomputed hash tables. Every few seconds the network publishes a random challenge. Each plot is checked against it; a plot “wins” when it contains a proof whose quality beats a threshold set by the current difficulty. The more space you have, the more lottery tickets you hold: your chance of winning is your share of the total space, the netspace shown on the dashboard. Checking a plot is cheap, so farming uses roughly the power of an idle computer.

Proof of time

Space alone is not enough: a farmer with a fast machine could try to rewrite history by grinding through alternatives. Chia therefore interleaves every block with a verifiable delay function (VDF) computed by timelords. A VDF takes a fixed amount of sequential time to compute, no matter how many processors you have, yet is quick to verify. The chain advances only as fast as real time passes, and that is what makes a block's position in time trustworthy.

Signage points and infusion

Time is divided into sub-slots of 64 signage points, about 10 minutes each. Challenges are issued at signage points; a winning proof must be infused into the chain a few signage points later, once the timelord has produced the corresponding VDF. That is why a block's page shows a signage point index and why several farmers can win nearly the same slot: the protocol allows it, and the chain picks the heavier branch. When two branches compete for a moment you see a reorg on the blocks page; in Chia these are usually one block deep.

Why it matters for you

Nothing about your transaction changes how blocks are found. What you control is the fee, which decides how quickly a farmer includes your spend once it is in the mempool.