Recently, on‑chain researcher ZachXBT said he no longer recommends hardware wallets such as Ledger due to recurring update issues, and proposed using a separate smartphone as a cold wallet instead.

Why a dedicated phone can work

An isolated device can store private keys offline, reducing exposure to network threats while preserving usability for occasional signed transactions.

Preparing the device

Start with a factory reset, install a minimal operating system image, and disable all radios and automatic updates to maintain an air‑gap.

• Remove SIM and SIM tray, and physically block cellular connectivity to prevent accidental reconnection.
• Disable Bluetooth, Wi‑Fi, NFC and any background services after the reset to preserve the offline state.
• Use a secure screen lock and full disk encryption where available to protect locally stored seed material.

Apps and workflow for air‑gap signing

Choose wallets that support offline signing; export unsigned transactions from an online device and import them to the phone via QR or USB transfer.

After signing, transfer the signed transaction back to an online device for broadcast, ensuring data flows only through controlled mediums.

Differences from hardware wallets

Unlike dedicated hardware devices such as Ledger or Trezor, a phone may not offer certified secure elements or vendor firmware audits.

However, a properly prepared phone provides a low‑cost air‑gapped alternative, requiring disciplined operational security and regular verification of signing apps.

Operational recommendations

• Keep the phone offline permanently except for controlled, one‑way data transfers using QR codes or a dedicated USB cable.
• Use well‑known, auditable wallet software that documents its offline signing process and supports seed‑phrase backups.
• Store backups of recovery phrases in secure, geographically separated locations to mitigate physical loss risks.

Turning an old smartphone into a cold wallet can be effective for custodial reduction, but it demands strict procedures and ongoing attention to device integrity.