Coinbase touts 99% cold storage as Binance Breach puts crypto exchange security under scrutiny

Following an October 29 hack in which Binance lost $6.3 billion, Coinbase highlighted that it stores more than 99% of customer funds in cold storage.

However, keeping assets offline introduces a separate challenge: preventing bad actors from gaining approval for fraudulent transfers.

What Coinbase says it does

In a recent blog post, Coinbase reported that its funds and systems remained secure. The platform maintains a minimal portion of assets in online hot wallets to facilitate withdrawals, while keeping the remainder offline. Furthermore, the company states that its dedicated Custody vault is entirely cold and kept segregated on-chain.

To govern asset movement, Coinbase divides private keys into multiple components and restricts the speed at which cold wallets can replenish hot ones. The setup allows suspicious activity to trigger a temporary halt, and includes kill switches capable of taking signing keys offline until issues are resolved.

Alongside these security measures, Coinbase notes that it maintains customer assets on a 1:1 basis and does not lend them out without explicit customer authorization. Notably, these assurances and security safeguards have not been independently verified for this article.

Storing keys versus approving transfers

The security breach at Binance demonstrates that protecting private keys is only part of an effective defense. As Cryptopolitan reported, hackers targeted engineers via a malicious download and a fraudulent job interview, subsequently leveraging stolen credentials alongside an internal AI tool to breach Binance’s wallet infrastructure.

Within four minutes, the perpetrators transferred 233.46 million XRP across five hot wallets. Reuters noted that Binance successfully froze or intercepted approximately $2.85 billion, though this intervention failed to halt the intrusion entirely as unauthorized transfers persisted for roughly four hours.

This security lapse underscores a vulnerability highlighted by Bitwise Chief Investment Officer Matt Hougan in a memo:

“They are, by design, the least-protected part of the system.”

— Matt Hougan, Bitwise Chief Investment Officer

Because the majority of Binance’s holdings remained secure in cold storage, the attackers targeted the less-protected funds. According to NCC Group, the incident delivers a broader lesson beyond mere cold storage implementation: security frameworks must be designed so that no single compromised staff member can authorize transfers independently.

Cold storage is not the same as cold custody

Keeping private keys offline makes direct theft significantly harder, but this precaution becomes ineffective if an adversary can manipulate the individuals or internal systems authorized to approve withdrawals. This distinction is why AMINA Bank separates the concepts of cold storage and cold custody.

While cold storage simply keeps private keys disconnected from the internet, cold custody introduces additional security dimensions. These include independent approval workflows, divided authorities, physical security protocols, established recovery plans, and comprehensive oversight policies designed to ensure that compromised employees or systems cannot execute unauthorized transfers.

Why institutions were already shifting

Demand for enhanced custody protections among large investors predated the security incident at Binance.

A survey conducted in January by Coinbase and EY-Parthenon, which polled 351 institutional investors, revealed that 66% viewed security and key-signing as top priorities when selecting custodians—a significant rise from just 8% in 2025.

The importance of regulatory compliance also climbed from 25% to 66%. Despite these evolving requirements, investor sentiment toward digital assets remained strong, with 73% indicating plans to expand their holdings.

Boston Consulting Group anticipates that custody will evolve into a core component of financial architecture. For banking institutions, secure asset storage is no longer sufficient; they also require dependable approval workflows, robust oversight, and multi-provider interoperability.

What has not been shown

Ultimately, Coinbase’s statistic regarding 99% cold storage does not provide a complete security picture. While it indicates where customer assets are reportedly held, it offers no absolute guarantee that every individual transfer remains secure.

Furthermore, no universal mandate requires exchanges to maintain a specific percentage of assets offline. Instead, IOSCO focuses on general principles of safeguarding customer assets, ensuring segregation, and performing independent record checks.

To date, the Binance breach has not triggered a permanent alteration in customer habits, and its wider market footprint appears contained. Bitwise data showed that Bitcoin dipped roughly 4% on October 30, tracking closely with the Nasdaq-100’s 3% drop. Concurrently, Grand View Research projects that the crypto-wallet market will scale from $15.5 billion in 2025 to $100.8 billion by 2033. However, that projection encompasses both hot and cold wallets and does not necessarily reflect a broad investor migration toward cold custody solutions.

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