There is little doubt that the use of biometrically-enabled passports will make life easier for border officials. However, should the chip carrying the biometric data be damaged, whether intentionally or otherwise, anyone inspecting the document will have to rely on its physical security features. So there is every reason to make these features as secure as those found in non-biometric passports. One option is to include a digital watermark, which not only prevents manipulation, but also protects blank documents (particularly useful in a decentralised issuing environment)