CVE-2019-15809

Vulnerability

CVE-2019-15809 is a timing side-channel vulnerability in ECDSA signature generation on smart cards manufactured by Athena SCS (and rebranded by other vendors). The vulnerable cards use the Atmel Toolbox 00.03.11.05, specifically the "fast" version of the ECDSA signature functions, which leaks the bit-length of the random nonce via timing [1][2]. The affected cards include Athena IDProtect (010b.0352.0005, 010e.1245.0002, 0106.0130.0401), Valid S/A IDflex V (010b.0352.0005), SafeNet eToken 4300 (010e.1245.0002), and TecSec Armored Card (010e.0264.0001, 108.0264.0001) [1]. These use the AT90SC chip from Inside Secure [3].

Exploitation

A local attacker who can obtain the required number of ECDSA signatures and measure their duration accurately can exploit this vulnerability. The attack requires a standard smart-card reader and a typical Linux laptop [1]. The attacker collects 2100 signatures on known messages for the secp256r1 curve; after collection, the private key can be recovered in a few minutes of processing on an ordinary computer using lattice techniques [1]. The total attack time, including signature collection and computation, is approximately 30 minutes [1]. The attack requires only a local attacker with physical access or the ability to interact with the card over a local interface; no privileged access is needed to initiate the signing operations [1][2].

Impact

Successful exploitation allows a local attacker to recover the full long-term ECDSA private key from the card [1][2]. This leads to complete compromise of the cryptographic identity, enabling the attacker to forge signatures, authenticate as the card's legitimate user, or decrypt any data protected by that key [2]. The impact is total loss of confidentiality, integrity, and authenticity for any system relying on the affected smart card for security.

Mitigation

The vulnerability is inherent in the Atmel Toolbox 00.03.11.05 firmware used on the affected cards [1]. As of the published date, no firmware update or patch is available. The Minerva research project recommends that affected cards use the "secure" (constant-time) version of the ECDSA functions if provided by the vendor [1]. Users should replace vulnerable cards with newer models that are not affected or switch to hardware implementing constant-time scalar multiplication [1][4]. The vulnerability is not currently listed on CISA's Known Exploited Vulnerabilities (KEV) catalog.