Structure of the block

Although all blockchains consist of linking blocks together to form an immutable ledger, different block structures can be adopted depending on the application. Permissioned and permissionless blockchains, for instance, have slight variations in their block structure. We'

We'll be using Bitcoin's permissionless block structure as a reference to try and identify its characteristics:

A block consists of the components mentioned in Figure 1.3. Block Header and Transactions are the most important parts of the block, as they are responsible for the hash value, which is the identity of the block. The Block Size is the size of the entire block. The Block Header contains all the metadata of the block, and the Transaction Counter has the count of transactions. Finally, all the Transactions are stored in the block.

As mentioned before, a blockchain starts with an initial block called the genesis block. If the chain is traversed backward from any given block, it will end up at the genesis block, proving that the entire chain is legitimate and valid. The genesis block is often statically coded in a public or permissionless blockchain, but it's created by the first participant in the case of the permissioned blockchain.