What Is a Cryptocurrency
The question isn't the technology. It's where the power sits.
Central systems bundle control at one body — efficient, convenient, and a single point everything hangs on. Decentralised systems spread it across many participants — resilient and independent, and a great deal more work to coordinate.
The problem
Nine participants. Start knocking them out.
Same nine, wired two different ways. Break the star, then break the mesh — and watch the second readout, because that is where the bill arrives.
Knock out a node
STAR · ONLINEAt full strength: star 8 · mesh 36
One hub routes for eight leaves. Click any node to knock it out — start with the hub in the middle.
The strength of a central system — clear responsibility, fast coordination, one address to complain to — is the same thing as its weakness. If the central body fails, is attacked, or simply decides wrongly, the whole system is affected at once. Every leaf was still running. None of them could reach another.
In the mesh there is no node whose loss stops the rest. Control and responsibility sit with many participants at the same time, so there is no single point to attack, switch off or lean on. That is what "hard to shut down through one point" actually means when you take it apart.
Now compare the second readout. The star needed 8 messages to reach agreement: every leaf speaks to the hub, and the hub decides. The mesh needs 36, because every peer has to hear from every other one — and that number grows far faster than the number of participants does. That is the trade in one line: decentralisation buys resistance to censorship and shutdown, and pays for it in efficiency. Neither wiring is better in general. The only honest question is which of the two you actually need here.
The definition
Three things this comparison usually gets wrong.
Tap each card for what is actually being traded.
Hands on
Turn one dial: how many have to agree.
Everything else in the comparison follows from that single number. Drag it and watch all three move together.
Currently 9 of them
A model, not a measurement. The source describes the mechanism, not the numbers: the message count is plain combinatorics — every pair speaking once — while the two indices are drawn to show direction, not to state a real-world figure.
The bridge
Where each model wins — and the question to ask.
Five entries, no verdict. The verdict depends on what you need from the system.
Blockchains don't simply copy the systems that came before them — they change the architecture: away from control at one central point, towards rules, verification and distributed responsibility. That is the logic the next lesson builds on, when it takes apart what a blockchain actually is.
Check yourself
Five questions.
Answers come straight from this lesson. Submitting completes it.