In contrast to common personal data (like the bearer's photograph, names, date of birth, etc.)
A chip protected by EAC will allow that this sensitive data is read (through an encrypted channel) only by an authorized passport inspection system.
There are several different proposed implementations of the mechanism, all of which must retain backward-compatibility with the legacy Basic Access Control (BAC), which is mandatory in all EU countries.
The specification selected for EU e-passports was prepared by the German Federal Office for Information Security (BSI) in their technical report TR-03110.
Terminal authentication (TA) is used to determine whether the inspection system (IS) is allowed to read sensitive data from the e-passport.