Blockchain 101

1. A blockchain is a chain of blocks that contains information or data.
2. Blockchains are used for the secure transfer of items. The item could vary from money to contracts.
3. Blockchain does not require a third party
4. A blockchain is a software protocol (like email)
5. Blockchain has to have access to the internet
6. Blockchain is also called meta technology
7. Blockchain affects other technologies
8. Once data is stored in a blockchain, it is extremely difficult to change it
9. Blockchain enables bitcoin, but is not bitcoin
10. Bitcoin is a digital token
11. Blockchain is a ledger
12. A block contains the information stored, which depends on the type of the blockchain
13. The first block is called a genesis block
14. A block has a Hash
15. A Hash is like a unique fingerprint of the block
16. A Hash is a combination of letters and numbers
17. If the data is changed in a block, the hash is also changes
18. Each block contains the data, the hash and the hash of the previous block
19. The genesis block has no previous hash
20. If the attacker changes the hash of a block, then the following block is invalid because they do not have the correct hash of the previous block
21. Changing a single block can make the entire chain invalid
22. Computers are becoming more and more powerful, so they can decode a whole chain quickly and make it all valid
23. Proof of work(POW) is used.
24. POW is a mechanism that slows down the creation of new blocks
25. A POW is a computational problem that takes a certain effort to solve
26. It takes some time to solve the POW
27. if the attacker tampers with a single block, they need to recalculate all the following blocks
28. P2P is another method used
29. Everyone on the network has a full copy of the blockchain
30. Each computer is called a node
31. When a user creates a new block, the block is sent to every user on the network
32. Each node needs to verify the block
33. Once verifies, the block is added
34. Al the nodes need to create a consensus and reject all blocks that are tempered with
35. To temper with a blockchain, the attacker needs to do three things
36. The attacker needs to tamper with all blocks on the chain
37. The attacker needs to redo the POW for each block
38. The attacker needs to take control of the majority (more than 50) of the P2P network
39. There are generally 4 steps of a blockchain
40. Step 1: A person requests a transaction
41. Step 2: The request is broadcasted to P2P from nodes
42. Step 3: The network of nodes validates the transaction
43. Step 4: Once the transaction is complete, the new block is added
44. A blockchain is resilient, so if a node is down, there are still many nodes running the system
45. Blockchain is quick and is faster without a third party
46. Blockchain is reliable
47. Blockchain is unchangeable (nearly)
48. Blockchain is secure
49. Blockchain does not have a centralized system
50. There are three general versions of bitcoin
51. 1.0: the blockchain is used in currency and payments
52. 2.0: Smart contract is implemented, and small computer programs are within blockchains
53. The computer programs execute automatic checks
54. 3.0: A DApp can have frontend Blockchain example code and user interfaces written in any language that can make a call to its backend, like a traditional App
55. There are also 3 main variants of blockchain
56. Public: anyone can verify and add a block of transaction
57. Private: works within a single organization. It allows only specific people to verify and add transaction blocks
58. Consortium: Only a group of organizations can verify and add transactions. It is also only controlled by pre-authorized nodes

There are not quite 101 points for a basic tutorial, but there are a lot more once you dive deeper. This is meant to give a basic overview of blockchain, so it is not meant to be a detailed guide.