Qubic continues to wreak havoc on Monero with multiple reorgs

By admin On Aug 26, 2025

Following exaggerated claims of controlling 51% of the Monero network, upstart mining community Qubic continues to throw its weight around.

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Brief periods of hashrate dominance have allowed Qubic to pull off multiple 9-block ‘reorgs’ of the privacy-focused blockchain.

However, Qubic claims to be self-limiting its actions, ensuring that such events do not pass the crucial 10-block threshold, which could allow for double-spending of coins.

What is a ‘reorg’?

Reorgs, or block reorganizations, occur when two conflicting states (forks) of a blockchain temporarily exist, without miners having agreed which is the legitimate, canonical chain. Once consensus is eventually reached, one of the forks is abandoned.

Transactions on the ‘losing’ fork may be lost if they were not included on the ‘winning’ chain.

Once a mining pool achieves a sufficient share of overall hashrate, it can engineer reorgs to its own advantage.

An example would be by inflating the perceived control over the network via ‘selfish mining,’ a technique that Qubic employed earlier this month to claim it had pulled off a 51% attack on Monero.

However, longer, more dangerous reorgs become possible with an increased share of the network’s hashrate.

The number of blocks involved in a given reorg is known as its ‘depth.’ Any incident deeper than the standard 10 blocks considered necessary for finality on Monero could lead to the possibility of ‘double-spending’ of tokens.

The prospect of any party having the capability to double-spend tokens completely undermines a blockchain’s economic security guarantee. Qubic knows this and, as a Monero miner, has a financial incentive to maintain faith in the network.

Founder Sergey Ivancheglo (a.k.a. CFB) effectively confirmed that Qubic is self-limiting the depth of reorgs to avoid double-spend attacks on centralized exchanges (specifically Gate).

How powerful is Qubic, really?

Some Monero loyalists have been fighting back against Qubic’s worrying shows of force, but brief periods of dominance mean that deep reorgs still find their way through.

At the time of writing, Qubic controls approximately 1.8 GH/s of the network’s 5.7 GH/s total hashrate and has mined just over 30% of the last 1000 blocks, according to data from MiningPoolStats.

However, the pool appears to be strategically varying their output to take advantage of lulls and periodically control a higher proportion of hashrate, during which time the longer reorgs are possible.

At times, Qubic’s dominance reportedly reached up to 57 of 100 blocks, as shown in the screenshots below.

Regardless of to what degree Qubic’s shenanigans rely on tricky timings and ‘selfish mining,’ the dangers posed to Monero are clear, and community members have offered up solutions over previous days.

BawdyAnarchist, a pseudonymous Monero community member, has proposed “Time Adjusted Blockweight,” which would see a steep increase in difficulty of mining blocks in conflicting chains according to time, not just depth, to attempt to make reorgs more expensive.

Another solution, dubbed “Detective Mining” by developer Riccardo Spagni (a.k.a. fluffypony), uses the ‘selfish’ mining pool’s own coordination messages to identify reorgs and cut them off.

For now, though, it seems that Monero must rely on Qubic keeping its word and its reorgs to nine blocks or less.

Not one to shy away from controversy, however, Ivancheglo continues to stoke the flames under the Monero community, recently pondering “Is it possible to deanonymize Monero transactions for one who defines which transactions to include into blocks?”

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