Coldcard Bug Highlights: Single-Sig Wallets Pose Security Risks – Multi-Vendor Multisig Emerges as the New Standard

A few weeks ago, a critical flaw in Coinkite’s popular Coldcard hardware wallets sent shockwaves through the Bitcoin community. A major bug in seed generation once again demonstrated that single-signature wallets—even those from top-tier manufacturers—are vulnerable. The solution? A paradigm shift from traditional single-key management to a modern, decentralized approach: multi-vendor multisig custody.
The Bug: A Seed Generation Flaw That Affects Us All
In July and August 2026, researchers uncovered a flaw in the random number generation used when setting up new Coldcard devices. The most concerning aspect? Under specific conditions, the seed phrase could become predictable if users relied solely on the device’s default randomness function. While Coinkite acted quickly by recommending additional entropy sources like dice rolls or manual keyboard inputs, the incident raises fundamental questions about security assumptions.
“Though the bug has been patched, this case proves that even the best hardware wallets aren’t foolproof,” says Juan Galt, cybersecurity expert and author of this article. “The real issue isn’t the hardware—it’s the principle: entrusting all Bitcoin keys to a single provider or even a single device introduces unnecessary risk.”
Why Single-Sig Is Inherently Risky—Bugs or Not
Most Bitcoin users still rely on single-signature wallets, where a single private key controls their funds. But this method carries several inherent risks:
1. Device failure or loss: If a hardware wallet is lost, damaged, or destroyed, the bitcoins are gone—unless you have a backup. But even then, you risk theft or physical coercion.
2. Key theft: If the private key is compromised—via malware, social engineering, or physical surveillance—the bitcoins can be stolen in seconds, and transactions cannot be reversed.
3. Vendor dependency: Many users assume hardware wallet manufacturers are infallible. The Coldcard bug proved otherwise.
“Bitcoin gives you control over your keys—but that doesn’t mean you should store all of them on one device or with one manufacturer,” emphasizes Galt.
The Solution: Multi-Vendor Multisig as the New Standard
To mitigate these risks, security experts have long advocated for multisignature wallets (multisig), where multiple private keys—ideally from different providers—are required to authorize a transaction. But diversity in both quantity and origin of keys is crucial.




“The key isn’t just in the number of signatures, but in the diversification of their sources,” explains the crypto security expert. “While storing three keys across Coinkite, Ledger, and Trezor is better than single-sig, it’s still a single point of failure—just distributed.”
The optimal approach is multi-vendor multisig, where keys come from fully independent providers using different security models and implementations. An example setup:
- Key 1: On a Coldcard device (Bitcoin-only, open-source)
- Key 2: On a Coldbit device (alternative hardware wallet with different firmware)
- Key 3: Split using Shamir’s Secret Sharing (SSS) across two or more paper backups or in encrypted cloud storage (e.g., via Glacier Protocol)
“Diversity in key sources makes it exponentially harder for an attacker to compromise all of them,” says the expert. “Even if one provider is breached or a device fails, the bitcoins remain secure.”
Practical Transition: How to Move to Multisig
For users accustomed to single-sig setups, switching to multisig may seem daunting—but it’s manageable. Here’s a quick guide:
1. Choose a wallet: Use a multisig-compatible wallet like Sparrow Wallet, Wasabi Wallet, or BlueWallet.
2. Generate keys: Create at least three private keys—ideally from different providers (e.g., Coldcard, Ledger, Trezor, or even software wallets like Specter-DIY).
3. Set the configuration: Define how many keys are required to sign a transaction (e.g., 2-of-3). The 2-of-3 setup is most common.
4. Secure backups: Store keys in physically separate, secure locations (e.g., safe, bank deposit box, trusted family member).
5. Test: Send a small amount of Bitcoin to verify the setup.
“Multisig requires more setup effort upfront, but the added security is worth it,” says Galt. “It’s no longer acceptable to use single-sig for large amounts or long-term storage.”
The Lesson from the Coldcard Bug: Diversification Is Key
The Coldcard incident served as a wake-up call for the Bitcoin community. It showed that even the best hardware wallets aren’t perfect—and that reliance on a single point of failure is dangerous. Rather than panicking, the bug should be seen as a catalyst for stronger security practices.
“Bitcoin returns control of your money—but that control demands personal responsibility,” Galt concludes. “If you truly want to protect your bitcoin, don’t trust one provider. Build a network of independent keys.”