3. Theoretical framework

Firstly, three points can be made that apply generally to steganography, but are particularly relevant to digital formats. Firstly, the smaller the information, the easier it is to conceal, and the better it is concealed. It therefore makes good sense to compress it before inserting it into any medium.

Secondly, it is wise to encrypt this data after compression. This has two important advantages. The second is a little more subtle: "good" encryption should make the encrypted data as indistinguishable as possible from purely random data (see article on Applied Cryptography [H 5 210]...