Passports and visas are currently undergoing a rapid change due to legislation being passed by authorities such as the US requirement that they should have machine readable biometrics embedded within them. What the governments are trying to accomplish is to positively link individuals to these identity documents. But if an impostor is capable of forging a passport, complete with embedded biometric, the document could still pass the biometric authentication step. To prevent the system from being compromised in this manner, a central repository of biometric templates could be incorporated. Then the system could compare its `live' biometric reading with the remote repository, rather than relying solely on the authenticity of the biometric embedded within the identity document. Using a central repository raises certain questions. Firstly, how will the system know which repository to query? How can the system be sure the passport is not fraudulent and referring queries to a fake repos...