Crypto Exchanges Tout Cold Storage Ratios After Binance's $6.36 Billion Hack
Key Takeaways
- •TRM Labs estimates attackers stole approximately $6.36 billion from Binance's hot wallet infrastructure, mostly within about 20 minutes, describing it as the largest hack in history, while Binance has disclosed only that the vast majority of user assets sit in cold wallets.
- •Gate launched a 'Proof of Security' framework showing 88.26% of its total assets in cold storage and claiming cold holdings could cover 104.58% of customer assets if hot wallets were fully drained, though the data is still undergoing third-party audit review.
- •Coinbase stated that more than 99% of customer assets are held in offline cold storage, with excess balances continuously rebalanced out of hot wallets.
- •Upbit reported holding 99.17% of its assets in cold wallets as of September 2026, the highest ratio among South Korea's five major KRW-based exchanges and well above the 80% regulatory minimum, with other local platforms ranging from about 80.54% to 94.76%.
- •Industry figures and regulators note that published cold-storage ratios are not directly comparable due to differing reporting periods and asset bases, and that offline wallets can still be compromised through flawed signing systems, weak access controls, or fraudulent employee approvals.
Cryptocurrency exchanges moved quickly to reassure users following last week's attack on Binance's hot wallet infrastructure, with several companies disclosing this week how they divide assets between offline cold storage and internet-connected hot wallets.
Gate launches "Proof of Security" framework
Crypto exchange Gate on Thursday launched a "Proof of Security" (PoSEC) framework, reporting that 88.26% of its total assets were held in cold storage and 11.74% in hot wallets. The company claims its cold storage could cover 104.58% of customer assets even if its hot wallets were completely drained.
"By publicly disclosing the distribution of assets between platform cold storage and hot wallets, PoSEC provides visibility into asset storage structures and their ability to cover potential losses under extreme scenarios," Gate said. It noted the data is still undergoing independent review by a third-party audit firm.
The Binance hack behind the disclosure push
Threat actors attacked Binance's hot-wallet infrastructure last week, stealing approximately $6.36 billion, most of it in about 20 minutes, according to TRM Labs, which described the theft as the largest hack in history. Binance CEO Richard Teng said the "vast majority" of user assets are held in cold wallets, but the company has not provided a precise split, even as several peers published specific ratios this week.
Coinbase says 99% of customer assets held in cold wallets
In a blog post on Wednesday, Coinbase said that more than 99% of customer assets are held in offline cold storage and that it continuously rebalances excess assets into cold storage.
"Binance's reported hot wallet incident has understandably left customers asking how Coinbase protects customer assets from something similar happening here," the exchange said.
Upbit reports the highest cold wallet ratio in South Korea
On Tuesday, Upbit, the largest cryptocurrency exchange in South Korea, confirmed it holds 99.17% of its assets in cold wallets, with the remaining 0.83% in hot wallets as of September 2026. Those figures are already disclosed to the Financial Supervisory Service.
"This represents the highest cold wallet storage ratio among South Korea's five major KRW-based cryptocurrency exchanges and is substantially above the regulatory minimum of 80%," a spokesperson for Upbit parent company Dunamu told Cointelegraph, in response to questions about South Korea's call for crypto exchanges to increase their cold storage ratios.
"Our aim is to keep our hot wallet holdings at an absolute minimum, with a target of maintaining them below 1% of customer digital assets," the spokesperson added.
Other major South Korean exchanges have reported lower cold-wallet shares. Financial Supervisory Service figures cited in earlier reporting put Bithumb at 94.76%, Coinone at 85%, Digital X, formerly Korbit, at 82.79%, and GOPAX at 80.54% at the end of September — all of which sit above the 80% regulatory minimum.
OKX's existing security overview, last updated on Sept. 18, 2026, said the exchange holds more than 95% of client crypto assets in cold wallets and less than 5% in hot wallets.
Ratios not directly comparable
The reported figures are not necessarily directly comparable, because exchanges use different reporting periods and may calculate cold-storage shares against different asset bases. The verification behind the numbers also differs: Upbit's figures are already on file with the Financial Supervisory Service, while Gate's are still undergoing independent review by a third-party audit firm.
Cold storage ratios, however, offer only part of the picture of an exchange's security. Offline wallets can still be exposed through compromised signing systems, inadequate access controls, or employees approving fraudulent transactions. Hong Kong's Securities and Futures Commission warned in an August 2025 circular that such weaknesses could compromise both hot- and cold-wallet infrastructure.
Related: Fed, OCC check US banks after Binance hack as experts flag security risks
Magazine: Asian crypto exchanges batten down the hatches as hacks surge: Asia Express
Source: Cointelegraph
