A watermark-based age verification system is provided in one implementation. The verification system may also verify a biometric template against a biometric sample. Shelf-life identification documents are provided in another implementation. Another aspect of the present invention analyzes image data to identify a face region or silhouette associated with a human subject depicted in the image data. The image data is adjusted, e.g., to center or align a face region within an image frame. A digital watermark is embedded after realignment. Another aspect authenticates or handles digital images that are captured at a first location and transferred to a second location via watermarking. In another implementation, first machine-readable code on an identification document layer is cross-correlated with second machine-readable code on the identification document. The first and second machine-readable codes are preferably sensed though different means, but can be cross-correlated to determine authenticity of an identification document.