The Monero community has been very sensitive to this. Qubic, a project focused on distributed computing, has significantly increased its percentage of Monero’s network hashrate. Kwame Nkosi, a former blockchain analyst at Deloitte, unpacks what this game-changing news could mean for the future. He warns about the danger of a 51% attack and how that could undermine Monero’s privacy-centric architecture.

Since Qubic went live on May 18, Qubic’s hashrate share of Monero’s global hashrate has increased tremendously, soaring from less than 2% to more than 27%. As of July 27, 2025, according to miningpoolstats.stream, Qubic is the largest Monero hashrate at 26.96% of Monero’s 6.12 gigahash per second (GH/s) hashrate. As a community, we are deeply concerned by this lightning-fast multiplier effect. They are specifically worried because Qubic is planning to get more than 51% hashrate dominance from August 2nd to 31st. The volatility in Qubic’s hashrate share, reaching 20-40% in July, adds fuel to these fears.

In this article we’ll explore the technical feasibility of a 51% attack on Monero by Qubic. We’ll take a look at the mechanics of uPoW, talk about what it means to Monero’s security model, and explore some possible mitigation strategies. Being informed of these risks and their potential remedies is key to upholding the Monero network’s privacy-by-default characteristics and circumference.

Understanding the 51% Attack Threat

All cryptocurrencies that use Proof of Work (PoW) are inherently at risk of a 51% attack. This type of attack occurs when a single entity or group gains control of more than 50% of the network's mining hashrate. With this much control, the attacker could interfere with the blockchain to their benefit.

For us, the “10 Block Decoy Bug” serves to underscore the very real vulnerabilities that exist in our systems. With sufficient hashrate control, those weaknesses become trivial attack vectors. This vulnerability made it possible for attackers to deanonymize users through the exploitation of weaknesses in the decoy selection algorithm.

  • Risk of transaction deanonymization: An attacker could potentially identify the real spend transactions, compromising the anonymity of Monero users.
  • Potential for double-spending: An attacker could double-spend Monero, undermining the integrity of the blockchain and the trust in the network.
  • Impact on ring signature security: An attacker could manipulate ring signatures, potentially revealing the true spent output and compromising the security of Monero transactions.
  • Vulnerability to decoy selection algorithm: A 51% attack could potentially exploit a flaw in Monero's decoy selection algorithm, allowing an attacker to identify and deanonymize users, as seen in the "10 Block Decoy Bug" vulnerability.

Qubic introduces a different consensus mechanism in the form of Useful Proof-of-Work (uPoW). Unlike other Proof of Work systems, uPoW is not based on miners competing to solve arbitrary cryptographic puzzles. Rather, it focuses that computational power on solving real-world problems. The idea of uPoW is pretty novel. Despite the original intent, its use in Qubic has understandably sparked fears of serious damage to other PoW cryptocurrencies, including Monero.

The Role of uPoW

The concern stems from the possibility of Qubic miners redirecting their hashpower towards Monero's network, particularly if incentivized to do so. This reallocation of hashpower has the potential to centralize the mining power, raising the threat of a 51% attack. Looking ahead, we have one more specific concern about Qubic’s uPoW system. It would potentially allow a type of “hashpower-for-hire” attack on Monero—where these Qubic miners can be incentivized to temporarily redirect their hashing power to perform a 51% attack.

The Monero community reads Qubic’s campaign as one of the most blatant and, in many ways, active 51% attack attempts ever. They argue that it’s incentive driven, not a code exploit. This perspective highlights the community's awareness of the potential threat posed by Qubic's increasing hashrate.

As you may have gathered though, the Monero community is not taking things sitting down while a 51% attack threatens just over the horizon. A number of mitigation strategies have been proposed and deployed to safeguard the network.

Mitigation Strategies for Monero

These steps proactively prevent bad actors from deanonymizing payments. They stop all manipulation of the blockchain, even if such an attacker has significant hashrate at their disposal.

Strengthening Security Measures

  • Increasing the ring size: Monero's ring signatures obscure the true spent output by referencing a group of possible outputs, with only one being the actual spend. Increasing the ring size to 16 has further enhanced transaction privacy, making it difficult to trace Monero transactions with certainty.
  • Improving decoy selection algorithm: The "10 Block Decoy Bug" was a flaw in Monero's decoy selection algorithm that was exploited in an attack. Improving this algorithm can prevent similar attacks in the future.
  • Enhancing wallet implementations: Wallet developers can implement measures to prevent attacks that exploit vulnerabilities in wallet software, such as the "10 Block Decoy Bug".

One mining pool—supportxmr.com—is organizing an effort to overthrow Qubic. Currently, it has 4,970 of those miners, giving them access to 28.7% of the network hash rate and the ability to successfully mine 36 of the last 100 blocks. This is a great example of the community’s initiative to combat the threat of hashrate centralization. The community’s rejection of Qubic’s campaign is further testament to the Monero community’s dedication to keeping the network secure, private, and truly decentralized.

Community-Driven Solutions

  • Implementing a more robust mining pool distribution: The Monero community can encourage a more decentralized mining pool distribution to prevent a single pool from controlling more than 50% of the network's hashrate.
  • Monitoring and responding to hashrate centralization: The community can monitor hashrate distribution and respond quickly to any centralization of hashrate, such as by implementing measures to prevent a single pool from dominating the network.

The Monero community is decisively standing guard, ready to respond, and taking the offensive at a possible existential threat from Qubic’s HasratChocolate. Monero is making robust new security efforts to secure its deeply privacy-friendly design. Simultaneously, it’s building out a decentralized mining ecosystem to ensure users’ continued trust and confidence in their network. As the fight continues, BlockchainShock will continue to bring you the latest news and information. We’ll be providing new, original analysis on the latest exciting developments in the Monero ecosystem.

The Monero community remains vigilant and proactive in addressing the potential threat posed by Qubic's increasing hashrate. By implementing robust security measures and fostering a decentralized mining ecosystem, Monero aims to safeguard its privacy-focused design and maintain the trust of its users. As the situation evolves, BlockchainShock will continue to provide updates and analysis on the ongoing developments in the Monero ecosystem.