1. An authentication method comprising: receiving optical scan data representing at least a portion of an identification document, the portion of the identification document comprising a first region including a photographic representation of an authorized bearer of the identification document; comparing geometric characteristics of the first region from the data representing the portion to predetermined geometric characteristics of the first region; based at least in part on a result of said act of comparing, adjusting a detection process; and detecting steganographic encoding with the adjusted detection process to obtain information steganographically encoded in the photographic representation of the authorized bearer of the identification document.