Data hiding using compressed archives

Abstract

The need to avoid suspicion in a potential observer/investigator, though it can be seen as a weak requirement for the protection of transmitted data, it can be extremely useful. For example, once discovered that the data has been protected by means of certain security tools, a malicious user that is strongly interested in such data could make a great effort in trying to remove the protection, for example, by cracking the password or by exploiting the vulnerabilities of the algorithm that was used to protect the data. Hence, to transfer information in a secure way, it is sometimes better to hide it inside other data, rather than protecting it in a conventional manner. One of the most important techniques in data hiding is steganography. In this work we propose a novel steganographic method which enables to hide information by using a compressed archive as information carrier. The method we propose uses these compressed archives, together with their relative hierarchical structure, to hide bits of information. We remark that by means of our method the hidden information does not have any semantic relation with respect to the content of the compressed archive, whereas such relation will concern how the archive (and the relative sub-archives) was compressed, i.e., what compression algorithms and relative parameters were used, as well as how this operation was performed. Since it is a common practice to send compressed data by means of a communication channel, we believe that our proposal can be a valid tool for steganographic purposes, since the suspect generated in a potential observer could be considered almost negligible.