  We propose a simple universal (that is, distribution--free) steganographic
system in which covertexts with and without hidden texts are statistically
indistinguishable. The stegosystem can be applied to any source generating
i.i.d. covertexts with unknown distribution, and the hidden text is transmitted
exactly, with zero probability of error. Moreover, the proposed steganographic
system has two important properties. First, the rate of transmission of hidden
information approaches the Shannon entropy of the covertext source as the size
of blocks used for hidden text encoding tends to infinity. Second, if the size
of the alphabet of the covertext source and its minentropy tend to infinity
then the number of bits of hidden text per letter of covertext tends to
$\log(n!)/n$ where $n$ is the (fixed) size of blocks used for hidden text
encoding. The proposed stegosystem uses randomization.
