Circle warns of quantum threat as USDC spans 37 chains
USDC (USDC)
Editor:
Eugene Serbin
bitcoinethereumnews.com reports that Circle has issued a warning regarding the growing capability of quantum circuits to attack widely used blockchain signatures, citing a new low-width record of 813 logical qubits. This development creates a dependency problem across every host chain, wallet, custodian, bridge, and user account that must eventually accept a safer way to authorize transactions. Circle’s current contract documentation lists 37 mainnet USDC rows, but the company cannot unilaterally change the signature rules of Ethereum, Solana, or XRPL.
In an Aug. 31 disclosure, Circle told developers to inventory their cryptography and prepare for key rotation, noting that USDC was worth about $73.6 billion on Sept. 2. The 813 figure represents a resource-efficient design but does not describe a complete Shor attack or its error-correction overhead. A March 2026 paper estimated that a 256-bit elliptic-curve discrete-log attack could use fewer than 1,200 logical qubits and fewer than 90 million Toffoli gates.
Circle also corrected its hardware comparison, noting that Google’s Willow processor achieved 105 physical qubits, not 105 logical qubits. NIST standardized SLH-DSA in FIPS 205 and recommends organizations begin replacing quantum-vulnerable cryptography now. The practical trigger for migration is readiness, requiring networks to add verification rules and users to coexist with classical and post-quantum authorization.
Arc serves as one controllable layer within the 37-network system, offering a proving ground for hybrid designs. However, Arc cannot make USDC quantum-safe on Ethereum, Solana, or other mainnet rows simply by adopting a new design. The public challenge specification optimizes a reversible point-addition circuit for secp256k1, scoring submissions by multiplying peak logical-qubit width by average Toffoli-gate count.
How the market reacted
Whalio's own Binance spot order flow for USDC, measured when this story was written up on 2 September 2026. Not the outlet's figures.
USDC is trading at $1.00 with a 1-hour buy ratio of 44.8% and a 4-hour buy ratio of 49.9%, both sitting below the 24-hour buy ratio of 48.5%. This indicates that buying pressure is fading in the short term, as the 1-hour reading shows a distinct drop from the daily average. The 24-hour volume delta is -$92,345,867, meaning that sell volume has exceeded buy volume over the last day. CVD at the 24-hour close is -$41,534,989, confirming that net flow has been negative. Spot volume for the period is $3,075,710,042 across 525,015 trades. Net buying occurred in only 10 of the 24 hours, suggesting a lack of sustained accumulation.
The latest daily buy ratio of 50.2% sits at the 73rd percentile of the last 322 days, against a median of 48.4% - stronger buying than most days.
Was that an ordinary day?
The same Binance spot measurements for USDC, averaged over the days leading up to the story.
Over the preceding week, the 7-day average buy ratio was 48.5%, matching the current 24-hour reading exactly. Volume was 1.15x the average, indicating a busier than usual trading day despite the neutral buy ratio. There were 0 days of net buying in the past week, contrasting with the mixed 24-hour flow. The 8-day volume delta total was -$589,485,430, showing a consistent outflow trend over the longer period. This is an ordinary day for the coin in terms of buy ratio balance, but unusual for its elevated volume relative to the weekly norm.