Coldcard entropy vulnerability exposes single-signature risks, while multi-vendor multi-signature becomes the new baseline for Bitcoin custody

Coinkite's hardware wallet Coldcard has been exposed for a serious entropy vulnerability, which has gone undetected since 2021, resulting in over $100 million in Bitcoin being stolen, with victims mostly being users of single mnemonic wallets. The weak entropy allowed attackers to guess private keys through customized means, prompting the Bitcoin community to reassess the reliability of single-signature self-custody.Against this backdrop, multi-vendor multisig solutions are becoming the new custody baseline recommended by long-term holders. This solution requires users to construct multisig addresses using keys from different wallet vendors, such as Trezor Safe 7, Ledger Nano, and Casa recovery keys to form a 2-of-3 multisig, thereby reducing reliance on a single hardware vendor. Multisig can also defend against wrench attacks and has given rise to Bitcoin insurance services priced in BTC, such as AnchorWatch.However, multisig also has its drawbacks; users not only need to keep threshold keys but also need to save copies of the multisig script or template to independently recover funds when the wallet service is offline.