The International Civil Aviation Organisation (ICAO) is in the process of finalising standards for the next generation of travel documents. The organisation’s objective is to improve document security while simultaneously speeding up and improving passenger clearance procedures. In addition to proposing the facial image as the globally interoperable biometric, ICAO has developed a Logical Data Structure (LDS), which comprises 16 data groups (both mandatory and optional). To protect the data on the chip, ICAO has additionally proposed the use of digital signatures, supported by a Public Key Infrastructure (PKI). This article explains the principles behind public key encryption, sets out some of the foundation technologies and highlights the processes involved.