is closed. The use of shielding is optional. To assure interoperability and functionality of the security mechanisms listed above, ICAO and German Federal Office for Information Security (BSI) have specified several test cases. These test specifications are updated with every new protocol and are covering details starting from the paper used and ending in the chip that is included. Attacks Since the introduction of biometric passports, several attacks have been presented and demonstrated. Non-traceable chip characteristics In 2008 a Radboud/Lausitz University team demonstrated that it's possible to determine which country a passport chip is from without knowing the key required for reading it. The team fingerprinted error messages of passport chips from different countries. The resulting lookup table allows an attacker to determine from where a chip originated. In 2010 Tom Chothia and Vitaliy Smirnov documented an attack that allows an individual passport to be traced, by sending specific BAC authentication requests. In 2016 Avoine et al. published a survey on security and privacy issues in passport protocols, where a new technique to track passports is introduced, based on the response time of basic commands. Basic Access Control (BAC) In 2005 Marc Witteman showed that the document numbers of Dutch passports were predictable, allowing an attacker to guess/crack the key required for reading the chip. In 2006 Adam Laurie wrote software that tries all known passport keys within a given range, thus implementing one of Witteman's attacks. Using online flight booking sites, flight coupons and other public information it's possible to significantly reduce the number of possible keys. In some early biometric passports BAC wasn't used at all, allowing attacker to read the chip's content without providing a key. Passive Authentication (PA) In 2006 Lukas Grunwald demonstrated that it is trivial to copy passport data from a passport chip into a standard ISO/IEC 14443 smartcard using a standard contactless card interface and a simple file transfer tool. Grunwald used a passport that did not use Active Authentication (anti-cloning) and did not change the data held on the copied chip, thus keeping its cryptographic signature valid. In 2008 Jeroen van Beek demonstrated that not all passport inspection systems check the cryptographic signature of a passport chip. For his demonstration Van Beek altered chip information and signed it using his own document signing key of a non-existing country. This can only be detected by checking the country signing keys that are used