Coinbase published a report on the quantum threat: which blockchains are prepared?

On April 21, 2026, Coinbase’s Independent Advisory Board on Quantum Computing and Blockchain published its first report. It states that the quantum threat is real and that blockchains must begin implementing cryptographic protections now.

• Coinbase’s advisory board released its first report on the quantum threat and post-quantum (PQ) cryptography.
• The general recommendation is to transition to PQ by 2035, but sooner is preferable.
• In theory, building a fault-tolerant quantum computer (FTQC) capable of breaking Shor’s algorithm is possible — the question is scaling.
• Among Layer 1 networks, Aptos and Algorand are the most advanced in PQ readiness.

On April 21, 2026, Coinbase’s Independent Advisory Board on Quantum Computing and Blockchain published its first report. It states that the quantum threat is real and that blockchains must begin implementing cryptographic protections now.

The introduction states:

“Quantum computing should not be ignored: we have high confidence that a fault-tolerant quantum computer (FTQC) will eventually be built. Therefore, blockchains and the broader cryptographic ecosystem must prepare for this possibility.”

Experts note that building a quantum computer capable of breaking Shor’s algorithm is extremely difficult, and there is no immediate threat. However, given current technological progress, the transition to PQ cryptography should be completed by 2035.

How long until blockchains can be broken?

According to the report, breaking Shor’s algorithm would require:

• an FTQC,
• millions of physical qubits,
• billions or trillions of two-qubit gates.

Error rates must remain below a critical threshold; otherwise, error correction introduces new errors.

Two approaches:

• reduce error rates,
• implement fault tolerance.

Only their combination enables a “self-sustaining chain reaction” of error correction.

Initially, 99.9999% accuracy was required; later reduced to 99.9% with higher overhead.

Recent advances:
Quantinuum and Google achieved ~99.9% gate fidelity on ~100 qubits. If scalable, this may be sufficient.

However, scaling remains a major engineering challenge.

Consensus and execution layers

Blockchains consist of:

• consensus layer,
• execution layer.

Transitioning to PQ requires replacing cryptographic primitives in both.

Consensus risks:

• validator signatures,
• VRFs,
• aggregation mechanisms.

Threshold signatures are not PQ-secure → protocol redesign may be needed.

Alternative: authenticated validator channels.

Migration strategy: gradual checkpoints.

Execution layer:

• simple signature replacement is insufficient,
• must preserve security,
• minimize costs,
• avoid major redesign.

Which blockchains are ready?

• Bitcoin: vulnerable UTXOs (~6.9M BTC exposed).
• Ethereum: EOA, validators, SNARKs, KZG issues.
• Solana: Winternitz Vault implemented.
• Algorand: already supports PQ signatures.
• Aptos: easier migration model.
• L2s: planning PQ upgrades.

Conclusion:
The industry is adapting, but the key question remains:
which will come first — PQ protection or practical quantum computers.

Editor: Alyona Nabok

#