Cardano (ADA) has secured the second spot among blockchains considered most capable of withstanding future quantum-computing threats. In a paper by Google Quantum AI, cited by Cardano representative dori, the ranking was based on each network’s readiness to transition to post-quantum cryptography.
Algorand Tops the List as Cardano Claims No. 2 Spot
The ranking assessed blockchains based on factors such as public key exposure, support for key rotation or protocol upgrades, and the window of vulnerability before transactions are confirmed.
According to Google’s findings, Algorand stands as the only network ahead of Cardano, having already tested quantum-resistant transactions in a live setting and enabled key rotation. This suggests that if quantum threats were to emerge today, Algorand is the only platform with the framework in place to transition users to more secure cryptographic systems.
Late Monday, Google’s Quantum AI team warned that quantum machines may be far closer to cracking the elliptic curve cryptography that underpins Bitcoin and Ethereum than previously believed. The revised estimate has sparked fresh urgency, with the analysts pointing to 2029 as a critical window for the crypto industry to upgrade its defenses.
According to the study, a powerful enough quantum computer could theoretically breach Bitcoin’s security in under nine minutes. Meanwhile, a separate report flagged weaknesses in Ethereum, outlining five possible attack routes that could expose up to $100 billion in assets, including DeFi protocols and tokenized funds.
 
Cardano is regarded as secure by design because it keeps public keys concealed for longer than many other blockchains. It utilizes the eUTXO model, in which spending keys remain hashed until the moment funds are used, adding an extra layer of protection for users. This mechanism ensures that potential attackers cannot access or observe the key until a transaction is initiated.
Other blockchains grouped at this level alongside Cardano include Dogecoin, Zcash, and Bitcoin Cash, all categorized as “tier 2” in the Google Quantum AI paper—indicating a structural advantage over many competitors. The report also outlines two additional categories: “vulnerable but preparing” and “broadest attack surface.”
Major blockchain networks such as XRP Ledger, Litecoin, and Bitcoin fall into the former group, as their public keys are more frequently exposed, potentially increasing susceptibility to quantum-based attacks. Meanwhile, Ethereum and Solana are considered to have the broadest attack surface, since their public keys are consistently visible—creating more opportunities for quantum attackers to exploit them.
That being said, Google urged crypto developers in its paper this week to begin upgrading blockchains to post-quantum cryptography now, rather than waiting for actual quantum threats to materialize.
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