Small Bitcoin Holders Move Coins After Coldcard Wallet Flaw Disclosure

Small Bitcoin holders moved coins on July 31 at a rate not seen since the collapse of FTX, according to CryptoQuant, as news spread that Coldcard hardware wallets had been generating guessable keys for five years.

Transfers of less than 1 BTC totaled 39,600 BTC (around $2.5 billion) that day, the firm's Head of Research Julio Moreno tweeted. The last comparable figure was 39,900 BTC on November 16, 2022, days after FTX failed. Daily active addresses rose from 645,000 on July 30 to almost a million on July 31, the highest since December 2024, with the jump concentrated in sending addresses rather than receiving ones.

Some of it went to exchanges. Deposits made up of sub-10 BTC transfers hit 7,300 BTC ($459 million) on July 31, the most since February 6, CryptoQuant said. Moreno linked the move to the Coldcard breach, saying people appeared to be shifting holdings "looking for safety," while noting the connection was not certain.

Notably, Bitcoin's price barely moved amid the wave of exchange deposits, suggesting that users were moving their coins to secure them rather than sell. Bitcoin is currently trading at $62,724, down 0.7% over the past day, per CoinGecko data.

The Coldcard flaw dates to a March 2021 firmware build error that left seed phrases drawn from far too small a pool. Galaxy Research logged three waves of thefts by Saturday, totaling 1,367 BTC across 4,585 addresses, up from $38 million when the flaw was disclosed and $70 million when Binance founder Changpeng Zhao warned holders.

A fourth is likely under way. Galaxy Research's Alex Thorn flagged sweeps across 15 consecutive blocks on Monday, running at roughly 45 times the normal rate, and after correcting a set that had wrongly included multisig addresses put the wave at 709 addresses and 448.73 BTC ($28 million). That would take the running total to about 1,816 BTC, near $114 million. Thorn added a caveat that no victim has yet confirmed the fourth wave, which rests on pattern matching.

Some sweeps were still sitting unconfirmed in the mempool and had opted into replace-by-fee, he said, meaning holders who act quickly and pay a high fee may be able to outbid the attacker. None of the addresses hit in the first three waves were multisig.

Kraken chief security officer Nick Percoco called the incident a "wake-up call for the entire hardware wallet industry." ColdCard’s Mk4, Mk5 and Q ship with certified secure elements, he noted, and their seeds still came out around 72 bits, because the certification covered the component while nobody verified which code path actually ran.