The cryptocurrency world recently witnessed a significant event as both Bitcoin Cash (BCH) and Bitcoin SV (BSV) underwent their first-ever block reward halvings in April 2025. These events, while programmed into the networks' code, triggered immediate and dramatic shifts in mining activity, leading to sharp declines in hash rate and network difficulty. The aftermath has sparked renewed debate about the long-term security and sustainability of these Bitcoin forks.
The BCH Halving: A Sudden Drop in Mining Power
On April 8, 2025, at 12:19 UTC, Bitcoin Cash reached block height 630,000—triggering its block reward reduction from 12.5 BCH per block to 6.25 BCH. This 50% cut in miner income had an almost instantaneous effect on the network’s health.
Miners, who operate large-scale hardware setups requiring substantial electricity and maintenance costs, quickly responded to the reduced profitability. Many shut down operations or redirected their computational power to more lucrative networks, most notably Bitcoin (BTC), where the reward remained unchanged.
According to data from CoinWarz, a leading crypto mining analytics platform, the Bitcoin Cash network experienced a freefall in both hash rate and mining difficulty immediately following the halving.
- Hash rate—a measure of total computational power securing the blockchain—plummeted from a peak of 4,001.5 petahashes per second (PH/s) on April 8 to just 785 PH/s, representing an 80% drop.
- Mining difficulty, which adjusts dynamically to maintain consistent block times, fell nearly 50%, dropping from 528 billion to 269 billion.
This dramatic decline raised serious concerns about the network's vulnerability to attacks.
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Network Security at Risk: The 51% Attack Threat
With hash rate and difficulty collapsing, the cost of launching a 51% attack—a scenario where a single entity gains control over the majority of the network’s mining power—dropped to alarmingly low levels.
Data from Crypto51.app, a site that tracks the theoretical cost of such attacks, showed that as of April 13, 2025, it would cost only $9,121 to rent enough hash power via NiceHash to overpower the BCH network for one hour. This is equivalent to roughly 41.11 BCH at current prices.
To put this into perspective:
- Attacking the Bitcoin network would cost approximately $520,000, over 57 times more than BCH.
- Ethereum’s hourly attack cost stood at $85,377, still nearly 10 times higher than BCH.
While NiceHash itself cannot guarantee sufficient capacity to execute such an attack on major chains, its pricing provides a reliable benchmark for assessing relative network security. A successful 51% attack allows malicious actors to reverse transactions, enabling double-spending—where someone spends the same coins twice.
This poses a real risk to exchanges and custodial services. An attacker could deposit BSV or BCH, wait for confirmation, withdraw funds or trade assets, then reverse the original deposit transaction—effectively stealing value without losing their initial coins.
BSV Follows Suit: Another Fork Faces Instability
Just two days later, on April 10 at 20:48 Beijing time, Bitcoin SV underwent its own halving event. Like BCH, the block reward was slashed from 12.5 BSV to 6.25 BSV, cutting miner revenue by half overnight.
The result? A similar exodus of miners.
BlockChair data reveals that BSV’s hash rate dropped from 3.06 exahashes per second (EH/s) to 1.83 EH/s—a decline of about 40%—in the days following the halving. Meanwhile, mining difficulty fell sharply from 420 x 10⁹ to 212 x 10⁹, according to Satoshi.io.
More tellingly, within the first 15 hours post-halving, only 35 blocks were mined on the BSV chain—55 fewer than expected under normal conditions. Since most blockchains aim for a consistent block time (approximately every 10 minutes), such delays signal instability and reduced network responsiveness.
The root cause lies in economics: when rewards are halved but coin prices remain flat or fall, marginal miners can no longer cover operational costs and exit the network.
Mining Economics and Network Resilience
The simultaneous struggles of BCH and BSV highlight a critical challenge for smaller blockchain networks: economic resilience after halving events.
Unlike Bitcoin, which has a massive global mining base and high market value that cushions halving impacts, forked chains like BCH and BSV lack sufficient demand and price momentum to absorb sudden drops in miner incentives.
As hash power dwindled:
- Transaction processing slowed.
- Confirmation times increased.
- Network security weakened significantly.
Although both networks have seen some recovery in hash rate since the initial shock, they remain far below pre-halving levels. In contrast, Bitcoin’s hash rate has continued its upward trend—suggesting that displaced miners have migrated to more profitable ecosystems.
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Frequently Asked Questions (FAQ)
What is a block reward halving?
A block reward halving is a pre-programmed event in many proof-of-work blockchains where the amount of cryptocurrency miners receive for validating new blocks is reduced by 50%. This typically occurs at set intervals—every 210,000 blocks for Bitcoin and its forks—to control inflation and mimic scarcity.
Why did the hash rate drop so sharply after the halvings?
The sharp decline occurred because miners’ income was cut in half overnight. For those operating on thin profit margins, continued mining became unprofitable. As a result, many shut down equipment or switched to more rewarding networks like Bitcoin.
Are BCH and BSV still secure after the halvings?
While both networks remain functional, their security has been significantly weakened. With lower hash rates, the cost of executing a 51% attack has dropped dramatically—making them more vulnerable compared to larger chains like Bitcoin or Ethereum.
Could this happen to Bitcoin during its next halving?
Bitcoin is less likely to experience such a severe drop due to its dominant market position, higher price per coin, and global distribution of mining power. However, smaller miners may still be forced out, leading to temporary consolidation of hash rate among larger players.
How do networks adjust to maintain block times after hash rate drops?
Blockchain protocols use dynamic difficulty adjustment algorithms. When fewer miners are active, the system automatically lowers the mining difficulty to ensure blocks continue being produced at regular intervals—typically every 10 minutes for Bitcoin-based chains.
Will hash rates recover for BCH and BSV?
Recovery depends heavily on price performance. If BCH or BSV prices rise significantly post-halving, mining profitability could improve enough to attract miners back. Otherwise, sustained low hash rates may become the new normal.
Final Outlook: Sustainability Beyond Halving
The recent halvings of BCH and BSV serve as cautionary tales for alternative proof-of-work blockchains. Without strong economic fundamentals—such as rising adoption, increasing transaction volume, or price appreciation—networks risk losing critical mining support when rewards are reduced.
For investors and users alike, these events underscore the importance of monitoring not just price movements but also underlying network health metrics: hash rate stability, difficulty adjustments, and attack cost estimates.
As the crypto ecosystem evolves, only those chains that can maintain robust security through decentralized miner participation will stand the test of time.
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