This was a great video intro to the blockchain.
In short, blockchain is a immutable linked list of hashes. Which can be used to solve the double spending problem in cryptocurrencies using proof of work and a persistent chain of records (blocks mined).
- PoW: The more hashing power the more trust worthy.
- PoS: The more coins the more trust worthy.
- PBFT: Hand selected trusted nodes.
- Randomized asynchronous algorithm: You trust nobody! Every single node is constantly re-evaluated. (Skycoin)
- Horizon State - Digital voting.
- Blockstack - Decentralized apps on Blockstack let you own your data so you can maintain your privacy, security and freedom.
- Cardano - Cryptographic currency implementing Ouroboros PoS protocol.