What is an orphan block?
An orphan block is a term used in blockchain technology, particularly in the context of Bitcoin. It refers to a block that is mined but not accepted and added to the main blockchain.
How orphan blocks occur
In the Bitcoin network, blocks are created by those who solve complex mathematical problems through a process known as mining. When a miner successfully mines a block, it contains a bundle of new transactions and a reference to the previous block in the chain. This creates a continuously forming blockchain.
However, sometimes two or more entities solve the mining problem simultaneously, creating multiple legitimate blocks. In such cases, only one block can become part of the main blockchain, while the rest become orphaned blocks.
Orphan blocks occur when a miner successfully mines a block but fails to have it added to the main blockchain. This can happen due to delays in propagating the block to other miners, resulting in a lack of consensus on which block to include in the chain.
In this case, miners do not receive a mining reward for their efforts. Instead, their blocks are discarded, and any transactions included in those blocks are returned to the memory pool to be included in future blocks.
How to prevent orphan blocks
To prevent orphan blocks, miners rely on a consensus mechanism called the longest chain rule. According to this rule, the blockchain with the most cumulative computational work is considered a legitimate chain. Miners compete to add blocks to this longest chain, ensuring the stability and integrity of the blockchain network.
Comparing Orphan and Stale blocks
Parent Blocks
An orphan block is a block that has no parent block, meaning it is not connected to the main blockchain. When two blocks are mined simultaneously, only one can be added to the chain, and the other becomes an orphan block.
Stale blocks, on the other hand, do have a parent block. They have successfully mined blocks that are not included in the lengthiest proof of work chain due to network latency or other factors.
Time Consideration
Orphan blocks occur when multiple valid blocks are created at the same time, and the network nodes need time to decide which block to include in the core chain. The orphan block remains unaccepted until it is connected to the longest chain.
Stale blocks are a result of latency or delays in block propagation. They are not included in the main chain due to being discovered after another block with the same parent has already been added.
Information Availability
When an orphan block is generated, the information contained within it is not immediately available to the network nodes. It remains unknown until it is connected to the main chain.
Stale blocks contain valid information, but they are not considered part of the longest proof of work chain. The information within them is accessible, but they are not recognized as a valid chain.
Involvement of Nodes
Nodes within the network play a crucial role in determining the acceptance of orphan blocks. They decide which block to include in the main chain based on the number of verified blocks.
Stale blocks are not dependent on node decisions. They are simply not included in the longest proof of work chain due to latency or other factors.
Involvement of Mining Pools
Orphan blocks can occur regardless of mining pool involvement. They are a natural occurrence when multiple blocks are mined simultaneously.
Stale blocks can also occur in mining pools, but they are becoming increasingly rare due to the implementation of low-latency communication channels.
What are Uncle Blocks in Ethereum?
In the Ethereum blockchain, uncle blocks are not included in the main blockchain but are still considered legit. They are created when multiple miners simultaneously mine new blocks on the ETH network. Uncle blocks play a significant role in maintaining the security and efficiency of the ecosystem.
Longer chain rule
For ETH, the blockchain with the longest chain is considered the valid one. However, due to the nature of decentralized mining, multiple miners can discover new blocks around the same time. This creates a situation where different valid chains can coexist temporarily.
Creation
When multiple valid blocks are mined simultaneously, only one of them becomes part of the core blockchain, while the others become uncle blocks. These uncle blocks contain valid transactions and are created by miners who were close to successfully mining the block but were not the first to do so.
Purpose
The inclusion of uncle blocks serves two primary purposes in the Ethereum network. Firstly, it incentivizes miners to continue mining even if they are not the first to solve the cryptographic puzzle. Miners who contribute uncle blocks are rewarded with a portion of the block reward, creating a fairer mining ecosystem.
Enhancing Security
Secondly, uncle blocks contribute to the overall security of the network. By including uncle blocks in the blockchain, Ethereum reduces the probability of a successful 51% attack. If an attacker were to rewrite the blockchain, they would also need to rewrite the uncle blocks, which adds a layer of security.