Adam Back's argument follows the "minimum trusted computing base" principle of Bitcoin security engineering. Bitcoin has gradually enhanced signature verification, transaction expression, and script rules through conservative upgrades from early P2PKH, P2SH multi-signatures to SegWit, Taproot, and Schnorr signatures. If a hardware wallet only needs to parse one transaction semantics, it can control display, amount verification, change address confirmation, and signature strategy within a relatively limited code and testing scope.

The capital path of multi-chain custody is "covering more assets - accessing more wallets and dApps - obtaining more transaction flow and users." However, with each additional chain, hardware or custodians may introduce new address encoding, transaction formats, Gas logic, token authorizations, contract calls, RPC dependencies, and blind signing risks. Security costs do not increase linearly: a special transaction on one chain or an error in a token authorization interface can become an entry point for attackers to breach user asset boundaries.

This contrasts with the strategies of hardware wallets like Ledger and Trezor that support multi-chain assets, and with Casa and Unchained that focus on Bitcoin multi-signature custody. The former views broad compatibility as a product distribution advantage, while the latter sees dedicated multi-signatures, geographic key isolation, and recovery processes as core services. The two architectures serve different risk preferences: frequent DeFi operators need compatibility, while long-term large BTC holders prioritize minimal permissions and verifiability.

Essentially, this is a choice of security architecture beyond technical alternatives: more features do not necessarily mean higher security; security depends on the matching degree of assets, permissions, and attack surfaces. The mechanism is that hardware wallets protect not the "chain," but the user's understanding and control over signing actions; when devices cannot fully display the real consequences of complex contracts, users will outsource security judgments to front ends, wallet plugins, or third-party interpretation layers. Bitcoin-specific devices transform security from "identifying all risks" to "defaulting to rejecting most risks."

ABAB News · Law of Cognition

The more features, the larger the attack surface
Compatibility creates convenience, isolation creates security
Unintelligible signatures mean handing assets to the front end