A file includes both content data (e.g., audio or visual information) and header data. At least some of the header data is steganographically encoded within the content data. This arrangement permits some of the header data to be recovered from the content, even if the content is transformed in a way that the file header information becomes lost. The encoded data can also be used to check for certain forms of file tampering. A variety of other steganographic techniques and applications are also disclosed.