The gap is closing
Quantum capability is climbing while the cost of attacking the signature scheme that secures most blockchain accounts is falling. Both figures below are read from the Circle Research Quantum Tracker on 10 September 2026. Circle Research is the source; no endorsement by Circle is implied.
The most error-corrected logical qubits any lab has publicly demonstrated.
What an attacker needs to forge the signatures securing on-chain accounts.
Smaller than most people assume, and closing from both directions. Classified programmes are not publicly visible, so the true gap may be narrower.
A receipt has to outlive its signature
A clinical evidence receipt is meant to be re-checkable years after the run. If the only thing binding a receipt to its claims is a signature scheme that a future machine can forge, the record quietly stops being evidence.
Capability and attack cost move towards each other
The tracker plots both lines in one view: demonstrated logical qubits climbing, and the logical qubits needed to break ECDSA falling as better attack circuits are published.
Arc already gives us the tool
Arc supports SLH-DSA, one of NIST's standardised post-quantum signature schemes. Arc transactions themselves are still ECDSA-signed, with hybrid support intended once a final scheme is chosen.
What this exchange does about it
SLH-DSA-SHA2-128fNIST FIPS 205- — Every receipt digest in this exchange is signed with SLH-DSA and verified before the receipt is anchored or paid.
- — The Arc transaction that carries the anchor is still signed with ECDSA, so the chain is post-quantum at the evidence layer and classical underneath.
- — That remaining classical leg stays an open hazard on the record, not a solved item.
- — No claim is made that this system, Arc, or USDC is quantum-safe end to end.