You've already forked specification
Josh Green
36 lines
2.7 KiB
Markdown
36 lines
2.7 KiB
Markdown
# Blockchain
|
|
|
|
## What is a Blockchain
|
|
|
|
The Bitcoin Cash Blockchain is a linear collection of [Blocks](/protocol/blockchain/block).
|
|
The "state" of the blockchain is calculated by sequentially executing each set of changes (in the form of [Transactions](/protocol/blockchain/transaction)) included in each Block.
|
|
|
|
When a Block is created it includes the [Hash](/protocol/blockchain/hash) of the previous block; this cryptographically ensures the Block's parent block cannot be changed without completely rebuilding the new block.
|
|
This chaining structure is similar to [Git](//git-scm.com) commits—where a block is analogous to a commit (a set of file changes), and each commit's parent is tied directly to its parent, forming a chain.
|
|
Unlike Git, in order to create a commit (i.e. a Block) a certain amount of work must be performed.
|
|
This [Proof of Work](/protocol/blockchain/proof-of-work) prevents blocks from being created instantly, and is the mechanic that prevents old history from being rewritten, since modifying a block would change its hash and disconnect it from its previous children.
|
|
Therefore, changing a block requires that each of the child blocks be recreated as well.
|
|
With this property, changing old blocks becomes nearly impossible as long as the Work to create a block is sufficiently time-intensive.
|
|
|
|
## Block Height
|
|
|
|
Blocks are applied sequentially, and therefore for a given chain, a block can be identified by its distance from the Genesis Block.
|
|
This distance is commonly referred to as `Block Height`.
|
|
There may be multiple blocks at the same `Block Height` if two blocks are built that share a previous Block's Hash.
|
|
Multiple Blocks with the same `Block Height` are often referred to as "sibling" Blocks.
|
|
Sibling Blocks can happen if a Block is created with sufficient Work before the mining Node has been made aware of the new (Sibling) Block.
|
|
Sibling Blocks are incompatible with one another, and eventually one will become orphaned.
|
|
The [Genesis Block](/protocol/blockchain#genesis-block) is the first Block in a chain, and has a `Block Height` of `0` (as its distance to the Genesis Block is zero).
|
|
|
|
As of [BIP-0034](/blockchain/forks/bip-34), the `Block Height` is included within the [Coinbase Transaction](/protocol/blockchain/block#coinbase-transaction).
|
|
|
|
## Work
|
|
|
|
The longest valid chain with the most [Proof of Work](/protocol/blockchain/proof-of-work) is generally considered to be the main chain.
|
|
Work can be quickly verified by evaluating the Block's [Difficulty](/protocol/blockchain/proof-of-work/difficulty).
|
|
The [Chain Work](/protocol/blockchain/proof-of-work#chain-work) is the summation of all work done up to a point on the Blockchain.
|
|
|
|
## Blockchain Reorganization
|
|
|
|
|
|
## Genesis Block |