Blockchain Security Is Simply Math

The main thing that makes Bitcoin, Ethereum, and other blockchains safe is simply math.

To put this in context, consider that on our planet there are around 7.5 x 10^18 grains of sand, while it is believed that there are around 10^80 atoms in the entire observable universe. This scale is crucial because blockchain security relies on a number terrifyingly close to that universal limit: 2^256 - 1, which is roughly 1.157920892 x 10^77.

It's simply a world with that many houses, and you simply pick a random house in this world. This house is open. Everyone can enter it, but the security isn't there; it's in the fact that no one would find your house to steal your money even if it's open, simply because of its place in this huge world.

Imagine that every atom in the universe is enumerated from 1 to 2^256. The specific order number of an atom is your private key, and its physical place is the address where people send you money.

So picking a random private key is technically pointing to a random atom in this universe. Basically, no one can find you unless you scream and say "Here I am!", which is equivalent to leaking your private key.