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.