How experts are rethinking Bitcoin security following the Coldcard incident

​In July, a critical vulnerability in Coinkite’s popular Coldcard hardware wallets shattered a foundational tenet of Bitcoin self-custody. A coding error in firmware versions dating back to March 2021 bypassed the device's secure hardware random number generator, relying instead on a more-easily predictable, deterministic software-based generator. This flaw allowed attackers to brute-force recovery seed phrases and drain over $100 million in Bitcoin from more than 1,000 supposedly secure, offline addresses.

The exploit has cast a chill over the Bitcoin market, striking at the very core of what the technology is supposed to represent. Hardware wallets have long been viewed as the gold standard for self-custody and the ultimate defense against remote hackers. When the most trusted air-gapped device in the industry fails due to a basic firmware build flag, it forces a painful reckoning for investors and self-custody advocates alike.

Today, security experts are divided. Some view this systemic vulnerability as a serious challenge to the self-custody model, arguing that self-custody remains too complex and risky for mass adoption if a single manufacturer update can quietly compromise funds held in more than a thousand different addresses. Others are using the incident to push for immediate, structural changes to how users secure their digital wealth. At the heart of this discussion are two broad approaches: security improvements for those willing to handle self-custody and potentially outsourcing security to institutional custodians.

Multisig across multiple vendors

Multisig addresses require signatures from multiple independent keys to authorize a transaction, such as in a two-of-three or three-of-five configuration. When set up properly, they can eliminate a single point of failure. True resilience requires more than just multiple keys; it requires diversifying those keys across different hardware manufacturers and software environments. If a Bitcoin holder uses three hardware wallets from the same manufacturer, a single supply-chain attack, firmware backdoor, or systemic software bug could simultaneously compromise the entire setup, defeating a large part of the purpose of the multisig architecture.

This vulnerability highlights a paradoxical security flaw inherent to specialized hardware wallets, as their very existence signals that they are being used to protect significant crypto asset holdings. Because a dedicated hardware device is designed solely for digital assets, possessing one immediately flags the owner as a high-value target for physical coercion or supply-chain interdiction. This "beacon" effect has led some prominent Bitcoin advocates to look elsewhere. For example, early Bitcoin investor Trace Mayer has historically noted his preference for a general-purpose Purism laptop. The idea is that, because Purism machines are general-use, open-source computers, they are less likely to be profiled as a cryptocurrency vault, theoretically reducing the risk of targeted physical or digital intervention.

To counter vendor-specific vulnerabilities, prominent security experts advocate for combining different hardware brands and implementing independent key generation methods. Craig Raw, the creator of Sparrow Wallet, has advocated for diversification across hardware-wallet manufacturers, explaining that one of his key motivations for developing Sparrow was the difficulty of creating a multisig setup using hardware wallets from different vendors. Additionally, to eliminate trust in the hardware manufacturer's internal random number generator (RNG) during key creation, many experts recommend manual key generation techniques, such as physical dice rolling.

For users who want this level of security but find managing several independent keys and seed phrases daunting, collaborative multisig service providers like Casa and Unchained Capital offer an elegant middle ground. These platforms assist clients by setting up a multisig arrangement (typically a 2-of-3) where the user retains the majority of the keys, while the provider holds a single key. This setup allows the provider to assist with transaction recovery or key replacement without granting them the ability to unilaterally access or move the user's funds. Casa CTO Jameson Lopp has previously described the company as providing “financial services without actually being a bank or having control over these keys,” while using multisig and key redundancy to give users greater control over their assets without requiring them to manage every aspect of key security themselves.

Covenants-related soft fork upgrades represent another proposed approach to strengthening Bitcoin’s security and scalability. By restricting how a transaction output can be spent in the future, covenant-enabled vaults could provide features such as spending delays and recovery paths. That said, it should be noted some of these benefits can already be approximated through multisig arrangements involving third party service providers, and none of the soft-forking covenants proposals for Bitcoin currently have widespread consensus.

Outsourcing custody to specialists

While self-custody remains the gold standard for sovereign ownership, a growing contingent argues that institutional custodial solutions are not only valuable but perhaps inevitable for mainstream adoption. The main argument is that direct interaction with the Bitcoin network's raw mechanics is too complex for the average user, making service providers a better fit for the masses. Strategy’s Michael Saylor previously sparked intense debate by arguing that Bitcoin is safer when held by regulated financial institutions such as BlackRock and Fidelity, comparing them favorably with “too big to fail” banks and dismissing fears of government seizure as concerns raised by “paranoid crypto-anarchists.”

This perspective remains deeply controversial among many Bitcoin users, where self-custody is widely viewed as the fundamental purpose of the network. Bitcoiners have long warned against the systemic risks of centralizing coins under a handful of custodians. The primary concern is history repeating itself in the form of a digital version of Executive Order 6102, the 1933 directive that forced Americans to deliver their gold to the Federal Reserve. Centralized honeypots make government confiscation or censorship trivial, undermining the censorship-resistant nature that gives Bitcoin its value in the first place.

Despite this tension, a middle ground is emerging where service providers build value-added layers on top of the base Bitcoin network, mirroring the historical development of the internet. Just as email is an open, decentralized protocol that most people access via centralized service providers like Gmail, the Bitcoin network may ultimately support a vast ecosystem of intermediaries. These providers offer far more than simple custody. Companies like Strategy (by leveraging corporate debt to package Bitcoin as equity) and Tether (by issuing a stablecoin partially backed by Bitcoin) represent early iterations of this trend.

Of course, there still needs to be a sufficiently large number of different custodians and sovereign users for this sort of structure to allow Bitcoin to retain its fundamental value proposition.

The Coldcard incident illustrates an uncomfortable reality that self-custody and cold storage do not eliminate trust completely. Users may eliminate reliance on a bank or centralized custodian while remaining dependent on hardware manufacturers, firmware developers, random-number-generation systems, software implementations, and their own operational security. Additionally, the proliferation of artificial intelligence has introduced a wave of sophisticated, short-term security threats that exploit legacy setups. However, over the long term, these same AI capabilities are expected to power more resilient defense systems.

At the end of the day, full self-custody is not a one-size-fits-all solution, and securing private keys against sophisticated attack vectors requires ongoing technical rigor. Although it is difficult for many Bitcoin purists to accept, many market participants find that trusting multisig service providers or even specialized, regulated custodians remains a safer and far more practical option than attempting to manage that complexity alone.