ZachXBT: Old iPhone may be safer than hardware wallets

Security researcher ZachXBT says a dedicated, older iPhone can provide stronger practical security for signing crypto transactions than some hardware wallets. He points to the phone’s hardened operating system, app sandboxing, biometric locks and a larger screen that can display transaction details more clearly.

ZachXBT framed the issue as a set of trade-offs. Hardware wallets isolate private keys from internet-connected machines to reduce the risk of remote key extraction. Recent thefts, however, involved attackers manipulating what users saw and collecting legitimate signatures for unauthorized transfers. In two incidents, attackers captured valid signatures after altering the signing interface: one incident cost about $1.5 billion and another about $50 million.

Data for 2025 shows a broad set of compromises. Chainalysis counted about 158,000 individual wallet compromises that year, affecting roughly 80,000 victims and producing about $713 million in losses across multiple attack types. Those figures indicate that protecting keys does not eliminate risk when a valid signature can authorize large transfers.

An older iPhone dedicated to signing can limit some risks. Apple’s Secure Enclave runs separate from the main processor, devices use biometric unlock, and a larger display can show readable transaction text. A dedicated phone can be kept free of email, messaging and browser extensions that commonly carry malware.

Technical limits remain. Secure Enclave uses NIST P-256 keys while Bitcoin and Ethereum commonly use secp256k1. Many wallet apps therefore use the Secure Enclave to protect access to encrypted wallet material but generate the blockchain signature elsewhere in software. That split leaves space for flaws in wallet implementations. In April 2026 a fake Ledger application that bypassed Mac App Store review was linked to more than $9.5 million in thefts from over 50 Mac users, an example of how software-level compromise can defeat device protections.

Industry engineers are pursuing standards and wallet designs to reduce signing risks. ERC-7730 defines a machine-readable way to translate contract calls into plain language so wallets can show assets, permissions and intent instead of raw hashes. A separate set of proposals for smart contract wallets would add on-chain restrictions such as daily spending caps, allowlisted destinations, withdrawal delays, separate keys for routine spending and emergency cancellation windows. Chainalysis offers pre-signing simulation tools that check transactions against organizational rules before signature.

Bitcoin security specialist Jameson Lopp continues to recommend dedicated hardware for cold storage and long-term custody, noting that keeping keys off internet-connected devices blocks many remote attacks. The industry is dividing custody into cold storage for large balances and active signing systems-policy wallets, secure phones or hardware devices-for day-to-day transactions to limit loss from stolen or coerced signatures.