Paul Hammant's Blog: Blockchains in pictures

This is a new article in a mini-series that started with ‘Old-School’ Merkle Trees Rock and Merkle Trees In Pictures. This one is attempting to show blockchains in pictures. I would also like to thank Ross Pettit and Prasanna Pendse for advice and tweaks for this article :)

Blockchain before the addition of a new entry on the ledger:

Blockchain after a new entry on the ledger (simple case):

Not so simple case:

Things get added in fits and starts, though, and entries on the ledger are not as linear as the simple case

Zoom out a little and it starts to look linear again:

Drilling deeper into the hashes:

Imagine a payload ‘A’ was just JSON like { "x": 123, "y": 456 }. And a hashing function h(A) was just shorthand for the SHA1 hash of that: 7f8a375ffad34cc488a7c7892d1a4bb81c653cbe. With some pseudocode we can illustrate what’s happening as things are added to the ledger.

At least, that is what the simple case looks like. And the boxes for the hashes are smaller that the ‘item’ because the latter could be much larger in size - crypto-currency assets at kilobytes, or MP3 songs (etc) at megabytes - it all depends on the purpose.