A recent debate sparked by ZachXBT suggests that using an old iPhone may be safer than storing cryptocurrency in a hardware wallet. Both devices function as signing tools, but the vulnerability lies in what a valid signature can authorize once it exists.
The issue is not with key isolation, which is addressed by hardware wallets, but rather with what happens after a user approves a transaction. Attackers have stolen billions of dollars from exchanges such as Bybit and Radiant Capital by manipulating what users see on their screens, collecting legitimate signatures for transactions that appear routine.
The iPhone argument gets complicated due to its hardened operating system, app sandboxing, biometric locks, and larger display, which can show more information than a hardware wallet. However, it still relies on the user noticing potential danger and refusing to approve a transaction.
Researchers are exploring ways to improve security through policy wallets that restrict what valid signatures can authorize, such as daily spending limits, allowlisted destinations, and withdrawal delays. Chainalysis's Hexagate product pushes this idea further by running pre-signing simulations for organizations before anyone signs.