Coincheck 2018 Hack and Bitcoin Custody Losses — CustodyStress

Documented custody cases associated with the Coincheck exchange in the Bitcoin Custody Incident Archive. The January 2018 hack of Coincheck resulted in the loss of approximately $530 million in customer assets — the largest exchange hack by value at the time of occurrence.

The most frequently documented recovery path in these cases is Exchange Support (2 of 2 cases). 100% of determinate cases resulted in some form of access recovery.

Coincheck was one of the largest cryptocurrency exchanges in Japan. On January 26, 2018, the exchange was hacked and approximately 523 million NEM tokens were stolen from a hot wallet. The exchange had stored the NEM in a single hot wallet without multi-signature protection, contrary to standard security practice. The Japan Financial Services Agency subsequently issued business improvement orders to Coincheck. The exchange was acquired by Monex Group in April 2018, which implemented improved security measures. Coincheck compensated affected NEM holders at approximately $0.81 per token, totalling approximately $425 million.

Coincheck held customer assets in exchange-controlled wallets. The NEM that was stolen had been stored in a single hot wallet without multi-signature protection or cold storage segregation — a custody structure significantly below the standard at the time. The concentration of assets in a single addressable hot wallet represented a fundamental custody architecture failure.

The hack exploited the single-hot-wallet architecture to drain the entire NEM balance in a single transaction. Affected customers lost access to their NEM balances. The custody failure affected customers holding NEM specifically — Bitcoin and other assets held by Coincheck were not affected. Compensation was subsequently paid by the Monex-owned Coincheck at a fixed rate.

Archive cases involving Coincheck document individual access failures associated with the 2018 hack. While the primary stolen asset was NEM rather than Bitcoin, the archive includes cases where Bitcoin holders experienced access failures associated with the exchange's subsequent regulatory and operational disruptions.