A Better Time Approximation Scheme for e-Passports

Abstract

E-passports are the new means of identification documents in border control points, where special reader devices named inspection terminals are installed to authenticate travelers. The authentication of e-passports to inspection terminals is based on biometric data stored in the formers, while the authentication of inspection terminals to e-passports is based on digital certificates. To check the expiration date of certificates, e-passports maintain an internal variable named effective date, which provides only an estimation of the current time. This introduces a serious threat on e-passports’ privacy. Specifically, e-passports may accept expired certificates, considering them as non-expired, due to the time difference between the effective dates of e-passports and the current time. Thus, in case an adversary obtains an expired certificate, he/she may impersonate a fake inspection terminal and compromise sensitive personal information (e.g., biometric data) from e-passports. This paper proposes a scheme that enables e-passports to update their effective dates based on the effective dates of other, more recently updated e-passports, in a secure and effective manner. In this way, more e-passports have a better estimation of the current time, reducing the time window in which an attacker can use an expired certificate. The proposed scheme minimizes the deployment complexity, since it does not require extensive modifications to the existing infrastructure, while at the same time maintains compatibility with the legacy system.