The presently claimed invention provides apparatus helpful for authenticating or protecting physical and electronic documents like financial documents and identification documents. One claim recites an apparatus including: an authenticator including or utilizing a processor which uses first information in a first portion of data associated with an object as a basis of first authentication information, the first information also being obtainable from a first portion of the object; and an incorporator including or utilizing a processor which incorporates the first authentication information in a second portion of the data, the first authentication information also being obtainable from a second portion of the object. Of course, other claims and combinations are provided as well.