Steganography is an information hiding application which aims to
hide secret data imperceptibly into a cover object. In this paper, we describe a
novel coding method based on Z2Z4-additive codes in which data is embedded
by distorting each cover symbol by one unit at most (+-1-steganography). This
method is optimal and solves the problem encountered by the most e cient
methods known today, concerning the treatment of boundary values. The
performance of this new technique is compared with that of the mentioned
methods and with the well-known rate-distortion upper bound to conclude that
a higher payload can be obtained for a given distortion by using the proposed
method
