Why Is CZ Telling Bitcoin Holders To Split Their Funds?
Binance founder Changpeng Zhao has urged cryptocurrency holders to spread funds across several wallets after a firmware flaw in certain Coldcard hardware devices was linked to the theft of more than 1,000 bitcoin.
“Even hardware wallets can have bugs. Even old wallets (with long history) can have bugs. How to mitigate? Split your funds in a few wallets maybe? This has a different set of risks. Nothing is 100%. Stay informed. Stay SAFU!,” Zhao, widely known as CZ, wrote on Saturday.
The advice changes the usual meaning of diversification in crypto. Investors have traditionally spread exposure across different coins to reduce price risk. The Coldcard incident suggests holders may also need to consider whether keeping all their assets behind one seed-generation process, wallet model or firmware version creates a single point of failure.
Splitting funds could limit losses if one wallet is compromised, but it also creates new risks. Owners must protect more recovery phrases, maintain accurate records and avoid mistakes while transferring or restoring funds. Wallet diversification therefore reduces concentration risk without removing the operational dangers of self-custody.
How Did The Coldcard Theft Happen?
Bitcoin users began reporting unauthorized transactions from Coldcard wallets on July 30. The attacker exploited a firmware flaw dating to March 2021 that reduced the quality of the randomness used to generate recovery seeds on certain devices.
A recovery seed is used to derive the private keys that control a wallet. When the seed-generation process lacks sufficient randomness, an attacker may be able to calculate possible seeds and reconstruct the corresponding keys. In this case, the theft did not require physical access to the hardware wallets because the private keys could reportedly be rebuilt offline.
Initial blockchain analysis identified about 594 BTC, worth roughly $38 million at the time, removed from around 500 wallets in a 25-minute period. Later research expanded the estimated loss to 1,082.65 BTC, valued at approximately $70 million, taken from 1,196 addresses over about 41 minutes.
Many affected wallets had remained inactive for years. That made the incident especially damaging for users who believed long-term offline storage had insulated them from exchange failures, phishing attacks and online account breaches.
Investor Takeaway
A hardware wallet protects assets from many online threats, but it does not eliminate risks inside the device’s firmware or seed-generation process. Large holders may need to assess concentration across wallet brands, devices and recovery seeds rather than treating one hardware wallet as complete protection.
Why Is A Firmware Update Alone Not Enough?
Coldcard maker Coinkite acknowledged the flaw, apologized and issued emergency firmware updates. However, installing patched software does not repair a vulnerable seed that was generated under an affected firmware version.
A recovery phrase created with weak randomness remains exposed even after the device is updated because the underlying private keys do not change. Coinkite has advised affected users to generate entirely new seeds on patched devices and migrate their bitcoin to addresses derived from those new phrases.
The migration process requires care. Moving funds from a potentially compromised wallet can alert an attacker monitoring the addresses, while typing a recovery phrase into an unsafe device or application could create another route for theft. Users must also verify destination addresses and retain access to the new backup before transferring their full balance.
The incident shows why firmware provenance and seed-generation history matter. A wallet that appears secure today may still control funds through keys created years earlier under a flawed software version.
Does Wallet Diversification Make Self-Custody Safer?
Using several wallets can reduce the amount exposed to any single hardware failure, software defect or compromised recovery phrase. A holder could divide funds across different devices, manufacturers or multisignature arrangements rather than relying on one seed.
However, simply buying several identical wallets may offer limited protection if they use the same affected firmware or seed-generation method. Effective diversification requires separating the sources of risk, not only increasing the number of devices.
Multisignature wallets provide another option by requiring more than one private key to authorize a transaction. Keys can be stored on devices from different manufacturers or in separate locations. The added security comes with greater setup complexity and a higher risk of permanently losing access if backups are poorly managed.
The Coldcard theft does not make self-custody obsolete. It shows that self-custody transfers responsibility from an exchange to the owner and the technology the owner selects. Hardware wallets remain useful against online theft, but their security still depends on firmware quality, manufacturing controls, backup procedures and how users distribute access to their funds.
For large bitcoin holders, the lesson is no longer limited to keeping coins off exchanges. It is to avoid allowing one device, one seed or one unnoticed software flaw to control an entire portfolio.