CVE-2019-15809 in Smartcard
Summary
by MITRE
Smart cards from the Athena SCS manufacturer, based on the Atmel Toolbox 00.03.11.05 and the AT90SC chip, contain a timing side channel in ECDSA signature generation. This allows a local attacker, able to measure the duration of hundreds to thousands of signing operations, to compute the private key used. The issue occurs because the Atmel Toolbox 00.03.11.05 contains two versions of ECDSA signature functions, described as fast and secure, but the affected cards chose to use the fast version, which leaks the bit length of the random nonce via timing. This affects Athena IDProtect 010b.0352.0005, Athena IDProtect 010e.1245.0002, Athena IDProtect 0106.0130.0401, Athena IDProtect 010e.1245.0002, Valid S/A IDflex V 010b.0352.0005, SafeNet eToken 4300 010e.1245.0002, TecSec Armored Card 010e.0264.0001, and TecSec Armored Card 108.0264.0001.
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Analysis
by VulDB Data Team • 09/20/2020
The vulnerability identified as CVE-2019-15809 represents a critical timing side channel attack against smart card implementations that utilize the Atmel Toolbox 00.03.11.05 firmware stack. This flaw specifically affects Athena SCS manufactured smart cards employing the AT90SC chip architecture, where the implementation of ECDSA signature generation contains a fundamental security weakness in the cryptographic execution process. The vulnerability stems from the deliberate selection of a performance-optimized but insecure implementation of ECDSA signature functions within the firmware, creating an exploitable timing discrepancy that reveals sensitive information about the cryptographic operations.
The technical flaw manifests through the use of a "fast" version of ECDSA signature functions rather than the "secure" alternative, despite the latter being available within the same firmware package. This choice results in a timing side channel where the duration of signature generation operations varies predictably based on the bit length of the random nonce used during the ECDSA process. The timing variations occur because the fast implementation does not properly mask the execution time differences that would normally be hidden in a secure cryptographic implementation. This timing leakage directly enables an attacker to perform statistical analysis on hundreds to thousands of signature operations, ultimately allowing the reconstruction of the private key through mathematical analysis of the timing data.
The operational impact of this vulnerability extends across multiple smart card models and manufacturers, affecting various versions of Athena IDProtect cards, Valid S/A IDflex V cards, SafeNet eToken 4300 devices, and TecSec Armored Card implementations. The local attacker requirement means that physical proximity or access to the card is necessary to measure the timing variations, but this access is often achievable in real-world scenarios where smart cards are used in authentication systems, digital signatures, and secure access control environments. The vulnerability essentially transforms the secure cryptographic operations into a recoverable key exposure, rendering the entire smart card security model ineffective against this specific attack vector.
The attack methodology follows established patterns described in the ATT&CK framework under the technique of "Timing Side Channel Attacks" and aligns with CWE-386 which identifies the weakness of exposing sensitive information through timing variations. This vulnerability represents a classic case of cryptographic implementation flaw where performance optimization has compromised security, creating a direct pathway for private key recovery. The attack requires significant computational resources for statistical analysis but can be automated and executed within reasonable timeframes, making it a practical threat to smart card security systems. Organizations using affected smart card implementations should immediately consider firmware updates, cryptographic algorithm re-evaluation, and potentially replacement of affected devices to mitigate this timing side channel vulnerability that fundamentally undermines the security assurances provided by ECDSA-based smart card implementations.