An interesting, albeit highly specialized, vulnerability has been uncovered in the world of hardware cryptocurrency wallets. My colleagues from the Ledger Donjon research division demonstrated a method for physically hacking popular Tangem NFC cards. The essence of the attack is a laser fault injection, which allows bypassing password protection and gaining full control over the assets on the device.
Technical Essence of the Problem
Tangem produces hardware wallets in the form factor of a plastic card, inside which a secure Samsung S3D232A chip with EAL6+ certification is installed. This chip generates and stores private keys, and also signs transactions via NFC. The standard security model assumes two factors: physical possession of the card and knowledge of the PIN code. Additionally, there is a mechanism for restoring access through a backup card.
The researchers focused on the logic of the SetPin instruction, responsible for changing the password. The firmware includes a check to determine if the device is allowed to be in a recovery state. Using a single nanosecond laser pulse directed at a specific area of the chip, it was possible to disrupt this check. As a result, the card accepted a new password without entering the old one and without using a backup.
Practical Implementation and Limitations
To prepare the attack, it was necessary to open the card's casing, expose the secure element, and connect it to a custom hardware platform. Using side-channel analysis, the exact moment of the vulnerable check's execution was determined. After calibrating the parameters for a specific model, each exploitation attempt takes about two hours.
However, the attack is invasive and physical. It leaves irreversible damage to the card, making it unsuitable for covert use. The only realistic scenario is a stolen or lost card. Additionally, the cost of laboratory equipment (laser setup, analysis tools) is estimated at around $250,000, and a high level of expertise in hardware security is required.
Tangem's Response and My Conclusions
Tangem rightly noted that the risk for ordinary users is practically negligible. They also pointed out a conflict of interest: Ledger Donjon is a division of a direct competitor. However, technically, the attack confirms an important nuance: EAL6+ certification guarantees the chip's resistance to certain classes of attacks, but does not protect against errors in the firmware logic running on top of that chip.
Personally, I believe this research is not so much a verdict for Tangem, but a reminder to the entire industry: the security of hardware wallets does not end with choosing a certified chip. Critical operations, such as changing a password, should have multi-layered protection, including independent checks and robust state encoding. For 99.9% of users, Tangem remains a secure solution, but this case is an excellent lesson for firmware developers.