This protocol enables to authenticate a terminal as a Basic Inspection System in order to gain access to the
logical MRTD.
The BAC Protocol is detailed in §E.2 of [BSI_EAC]. It relies on the symmetric Document Basic Access Keys
KENC and KMAC shared with the Basic Inspection System once the MRTD Holder has willingly offered his
passport to the Boarder Officer. This security function prevents an attacker from skimming the information
contained in the electronic document without the MRTD Holder authorization, as the authentication protocol
requires to optically read the MRZ information that is physically printed on the MRTD. If the BAC Authentication
succeeds, the Inspection System endorses the Basic Inspection System role with regard to File Access Control.
As a side effect, the protocol provides two session keys KSENC and KSMAC that are subsequently used for
establishing a secure channel with the Basic Inspection System. If the Basic Inspection System supports the
Chip Authentication mechanism described below, these session keys are only used to protect the Chip
Authentication public key. Once the Basic Inspection System has successfully re-authenticated itself using Chip
Authentication, they are replaced by the (stronger) session keys resulting from this latter protocol. If the Basic
Inspection System of the receiving State does not support Chip Authentication, it is assumed that its operating
environment is equipped with sufficient measures against eavesdropping.
The challenges used during the protocol and involved in the derivation of the BAC session keys are generated
using a random number generator including a post-processing based on the X9.31 standard. This post-
processing algorithm is compliant with the STANDARD security level defined by the French Certification
Scheme.
BAC Authentication is available only during the Operational Use phase of the TOE's life cycle. It is mandatory to
use it before accessing the logical information contained in the MRTD’s chip and before performing Chip
Authentication.
If a configurable number of consecutive errors are detected during signature verification of the BAC
authentication, the product increases the response time by a randomly chosen delay depending on a
configurable value. This security functionality prevents brute force attacks on the private keys stored in the
MRTD´s chip. Three possible thresholds can be specified during the initialization of the MRTD, each one
introducing an additional delay in milliseconds.