Orphan Block

An orphan block in the blockchain refers to a block created and validated by the miner but not accepted by the blockchain. These blocks exist in the network because the blockchain is short on time; thus, it does not accept them.

These blocks do not have a parent or a preceding block before them. Therefore, they are left alone from the rest of the blocks. As a result, they remain independent in the network. However, it does provide space for stale blocks to develop after orphan blocks in the blockchain.

Orphan blocks are blocks rejected by the blockchain due to time lag. They form a separate route with no main root or parent block. In short, they remain detached from the original blockchain. However, the transactions within these blocks are genuine and get validated by the miner. Thus, they are not invalid and are possible in every blockchain network. For example, reports suggest that orphan blocks in Ethereum 2.0 can also exist as ommer blocks.

The blockchain process starts with the miner's validation of the transactions conducted in the network. During this period, they use computational power to solve mathematical proofs that state the validity of these transactions. If a miner successfully verifies many transactions, the network rewards them with crypto tokens. Later, the network will add this block to the pre-existing chain. Usually, a Bitcoin blockchain requires 10 minutes to perform the same. However, if the time exceeds, the blockchain will reject the block. Thus, the network will leave this block and proceed over other blocks. As other blocks get validated, they continue to form the blockchain. However, the rejected block is left alone and becomes an orphan block.

The challenge occurs when two miners compete to add their blocks to the network. That is, the network splits into two parallel versions of the blockchain. The longer chain will continue out of the two, and the shorter one will be rejected. Although both are valid, the longer chain is attached to the main blockchain. However, the transactions of rejected blocks are stored in the memory pool.

For example, Bitcoin orphan blocks were prevalent in older versions of Bitcoin Core software. However, the release of Bitcoin Core v.0.10 in 2015 made it impossible to exist.

Let us look at the examples that exist in the blockchain networks of major cryptocurrencies:

Example #1

Suppose Yujin, Kasol, and Yameen are a class of miners operating on the Ethereum blockchain. Frequently, they validate the crypto transactions by solving proofs and problems. In return, they receive ETH as a mining reward. However, Kasol and Yujin were very competitive in their work. They wanted to add as many blocks as possible to the network. But, at one point, both attempted to add blocks to the system. In this race, the network splits the blockchain into two parts. One added Kasol's block, and the other chain added Yujin's block. However, after some time, the network added Kasol's block to the blockchain, and Yujin's block was rejected.

In this case, Kasol's block had a longer chain than Yujin's. As a result, the latter's block was left alone, and the parent blockchain continued with Kasol's block.

Example #2

A rare event occurred on the Bitcoin (BTC) blockchain when an orphan block was recorded. According to BitMEX, a Twitter account known for its blockchain research, an orphan block was created at 7:54 CEST, specifically block number 578141. Although the block was valid, it was not included in the Bitcoin blockchain due to a delay in its propagation and validation. This allowed a competing block to be confirmed more quickly and recognized as the winner. This phenomenon, while rare, has happened before and does not cause issues for the BTC network, which automatically syncs with the fastest chain.

The last orphan block on the Bitcoin blockchain was recorded in February 2019, making these events increasingly rare compared to previous years. In 2017, 60 orphan blocks were recorded, dropping to five in 2018 and only two this year. The time difference between the orphan block and the winning block is typically just a few seconds or less. In the case of this morning's orphan block, the difference was just under three seconds. The Bitcoin consensus algorithm recognized the fastest blockchain as the official one, leading to the exclusion of the orphan block in favor of the competing block, which had a lower timestamp. Despite this, there is no loss of transactions or funds, as the transactions from the orphan block are usually included in the next block.

Orphan blocks are a popular concept among miners that occurs during the validation process. However, the orphan block challenge also serves as an essential factor for the network. Let us look at its significance in the crypto market:

• Functioning and Security: Orphan blocks usually occur during mining glitches. However, they help in understanding the security code of the blockchain. If any chain turns blocks into orphans, there is an issue with the block time. As a result, developers focus on erasing them from the main blockchain. Hence, the miners can easily add their blocks to the network.
• Chain Recognition: It helps network participants, such as miners and nodes, recognize the parent blockchain. In short, they can easily distinguish between the rejected and accepted blocks. With the rejected blocks sidelined, the miners can verify transactions and add blocks to the network.
• Network Enhancement: The occurrence of the blocks enables the nodes to enhance the network. They detect the bugs that cause time lag and try to reduce them. As a result, the rate of orphan blocks was reduced in the updated version. For example, Ethereum's block time is 10 to 19 seconds. Thus, the occurrence of orphan blocks in Ethereum may be low due to lower block time.

Understanding the differences between an orphan block, an uncle block, and a stale block is crucial for grasping how blockchain networks handle competing blocks and ensure consensus.