Paul Hammant's Blog: Merkle Trees In Pictures (assuming you know what a SHA1 hash is)
Earlier today I posted Old School Merkle Trees Rock. Not so much about ‘rocking’ this time, more about depictions of plain Merkle trees that are are not what you usually encounter online.
I regularly see a balanced representation of Merkle trees. This one is from wikipedia (today):
^ one node from two nodes, each from two more nodes, and each of those having some notion of content (‘block’ in this case).
Lack of symmetry (irregularity) and change over time
One trouble with that representation is that a lack of symmetry is normal in a Merkle tree, and that is not shown in this style of diagram.
Secondly, there’s no representation of change over time, and how Merkle hashes work in respect of that.
I’ll try for that (SVG inline):
Content as well as SHA1
Classic diagrams of Merkle trees don’t show content as something tangible. Often content isn’t represented at all.
I’ll recycle the picture from the other blog entry today:
^ content can appear anywhere in a Merkle tree, and directories can be empty, too.
Merkle trees typically change below root at a fixed location.
Note: Err, it appears that OmniGraffle is slightly messing of the <TEXT/> nodes of SVG. At least in Chrome, Firefox and Safari that’s true today. When that’s fixed, I’ll update the SVGs, but I think you can follow, and we have to put the knife in the PNG era sooner or later (where we can).
And then, I couldn’t leave it as was … I went ahead and fixed it by hand