ME News reports that on August 27 (UTC+8), a severe entropy vulnerability was exposed in Coldcard, a hardware wallet by Coinkite. The flaw, undetected since 2021, led to the theft of over $100 million in Bitcoin, primarily affecting users who relied on single-mnemonic wallets. The weak entropy allowed attackers to guess private keys through customized methods, prompting the Bitcoin community to reevaluate the reliability of single-signature self-custody. In this context, multi-vendor multisig has emerged as the recommended new custody baseline for long-term holders. This approach requires users to construct a multisig address using keys from different wallet vendors—for example, combining Trezor Safe 7, Ledger Nano, and Casa recovery keys into a 2-of-3 multisig—to reduce reliance on any single hardware provider. Multisig also defends against wrench attacks and has enabled Bitcoin insurance services like AnchorWatch, which are denominated in BTC. However, multisig has drawbacks: users must not only safeguard the threshold keys but also retain copies of the multisig script or template to independently recover funds if wallet services go offline. (Source: ChainCatcher)
Coldcard Entropy Vulnerability Exposes Single-Signature Risks; Multi-Vendor Multisig Gains Traction
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Summary
A newly disclosed entropy flaw in Coldcard hardware wallets has exposed single-signature systems to risk, with over $100 million in Bitcoin stolen since 2021. The flaw allowed attackers to guess private keys, driving the Bitcoin community toward multi-party computation (MPC) and multi-vendor multisig solutions. Solutions such as Trezor Safe 7, Ledger Nano, and Casa recovery keys now form 2-of-3 architectures. These setups protect against theft and enable BTC-denominated insurance through AnchorWatch. Users must store scripts for offline recovery, often using decentralized storage solutions.
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