Weakening ePassports through Bad Implementations

Different countries issue an electronic passport embedding a contactless chip that stores the holder data (ePassport). To prevent unauthorized reading of the sensitive information present on such chip an access control mechanism based on symmetric cryptography, the Basic Access Control (BAC), has been introduced. In this work we present the flaws we have found out in some implementations of the software hosted on ePassport chips and how BAC is affected. In particular we show how it is possible to discern the different software versions used on the chip over time through some their peculiar fingerprints. This information can be used to shrink the BAC keys space making the protocol weaker. In addition, we show the presence of a defective function to exchange random material during the BAC procedure that opens a door for a MITM attack. The results of this paper could be exploited as a first guide for reviewing and refining existing ePassport implementations.