The Minimum Viable Blockchain (<a href="https://www.igvita.com/2014/05/05/minimum-viable-block-chain/" rel="nofollow">https://www.igvita.com/2014/05/05/minimum-viable-block-chain...</a>) is by far the best introduction to blockchain I have read.
I always find this introduction (including a "live demonstration") by Anders Brownworth very illustrative: <a href="https://anders.com/blockchain/" rel="nofollow">https://anders.com/blockchain/</a>
Here is a really great video [1] which really made blockchains click for me. I believe this was posted on HN a while back.<p>[1] <a href="https://anders.com/blockchain/" rel="nofollow">https://anders.com/blockchain/</a>
This article has a few issues.<p>First, you spend the first half of the article explaining a signature scheme that isn't based on cryptography. It isn't really clear what that part of the article is actually about.<p>> "Signed by John" <- John encrypts this line using his private key<p>This isn't how message signing works. It has all the problems you described in the first part, before you introduced asymmetric encryption.
I've found this a really clear and helpful explanation of blockchain concepts in the past: <a href="http://www.michaelnielsen.org/ddi/how-the-bitcoin-protocol-actually-works/" rel="nofollow">http://www.michaelnielsen.org/ddi/how-the-bitcoin-protocol-a...</a>
One thing that bothers me about all blockchain demos or tutorials is that they work on the concept of tracking outputs of transactions rather than just maintaining state.