The present invention relates generally to identification documents. One claim recites an apparatus to authentic an identification document. The identification document comprising first machine-readable information including a first plural-bit message, and semantic information carried on or in the identification document. The apparatus includes: a first reader to read the first machine-readable information to obtain the first plural-bit message; a second reader to obtain information from the semantic information carried on or in the identification document; an electronic processor programmed as a decryption unit to decrypt the first plural-bit message or the information obtained from the semantic information; and an electronic processor programmed as a decision unit to determine whether the identification document is authentic based at least in part on the first plural-bit message and the semantic information. Other claims and combinations are provided as well.