An issue was discovered in Arm Mbed TLS before 2.16.6 and 2.7.x before 2.7.15. An attacker that can get precise enough side-channel measurements can recover the long-term ECDSA private key by (1) reconstructing the projective coordinate of the result of scalar multiplication by exploiting side channels in the conversion to affine coordinates; (2) using an attack described by Naccache, Smart, and Stern in 2003 to recover a few bits of the ephemeral scalar from those projective coordinates via several measurements; and (3) using a lattice attack to get from there to the long-term ECDSA private key used for the signatures. Typically an attacker would have sufficient access when attacking an SGX enclave and controlling the untrusted OS.
Published: 2020-04-15Modified: 2024-11-21
CVSS 2.0LOW 1.9
CVSS:2.0/AV:L/AC:M/Au:N/C:P/I:N/A:NCVSS 3.xMEDIUM 4.7
CVSS:3.x/CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N