Tangem Cards identified as susceptible to brute-force hacking attempts
In a recent finding, security researchers at Ledger Donjon have identified a vulnerability in the secure channel implementation of Tangem cards. This vulnerability, known as a "tearing attack," could potentially allow attackers to bypass the card's security measures and perform brute-force attacks.
The vulnerability arises from the card's electromagnetic emissions, which vary based on the correctness of the password used for commands encryption. An attacker, with precise timing and understanding of the device's internal processing cycles, could power off the card before error management occurs if the card fails to decrypt data due to an incorrect password. This would bypass the card's security delay mechanism, enabling them to try approximately 2.5 passwords per second.
The attack primarily affects the card's flash memory or other non-volatile storage where crucial state information, like an authentication failure counter, is kept. The success of such an attack depends on the ability to interrupt the card's power supply during its critical state updates, potentially circumventing security mechanisms if the card's applet does not use built-in platform protections like atomic transactions.
The vulnerability could allow an attacker to attempt one million common passwords in about 4.5 days. However, the estimated duration for trying all possible combinations for a Tangem card locked with a 4-digit PIN would take about 5 days, for a 6-digit PIN, this duration extends to approximately 520 days, and for an 8-digit PIN, it can reach up to approximately 143 years.
Tangem was informed of the vulnerabilities and recommended enforcing an access policy within the Tangem app to require users to select robust passwords and upgrading passwords if they do not comply with the policy. Unfortunately, Tangem cards are not upgradable, so the secure channel implementation vulnerability cannot be patched in existing products.
To protect against brute-force attacks, users are advised to use strong passwords (at least 8 characters with a mix of digits, letters, and symbols). The Java Card platform includes built-in protections like atomic transactions to mitigate this kind of vulnerability, but failure to call the provided platform API can leave a card vulnerable to such attacks.
Ledger Donjon came across a secure channel implementation in their evaluation, but it is never activated. They successfully enabled it by altering a single boolean value in the smartphone application. Despite their efforts, they were unable to successfully attack the authentication of the "read wallet" command. They still have other ideas to try, but they cannot definitively confirm the vulnerability of the implementation to such an attack.
The estimated cost for the attack setup using the tearing attack on the secure channel implementation of Tangem cards is under $5,000. The exploit relies on the interruption of power to a smart card during an operation, preventing its completion. This is known as a "tearing attack," a method commonly used to attack embedded systems like those in smart cards.
In conclusion, while Tangem cards offer a high level of security, this vulnerability could potentially allow attackers to bypass the card's security measures and perform brute-force attacks. Users are encouraged to use strong passwords and be aware of this potential risk. Tangem has been informed of the issue, but due to the cards' non-upgradable nature, the vulnerability cannot be patched in existing products.
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