In an exemplary embodiment of this invention there is disclosed a mobile wireless terminal (50) that includes a transceiver (52) for coupling the mobile wireless terminal to a wireless network operator (60), a controller (54) and a memory (56). The memory may be assumed to store a file system program (56A) executable by the controller, and to be operable to store a file having a file data portion (14) for containing file data and a data structure, such as a file header (10), having fields for containing values. A plurality of the fields contain a value of a public cryptographic key (24) associated with a file creator, a seed value (26), an encrypted seed value (28) obtained by encrypting the seed value with a private cryptographic key of the file creator, and a file integrity value (30) obtained using the encrypted seed value and the file data. By the use of the preferred embodiments a file can be traced-back though a plurality of file handlers to a creator of the file.