  In this article, one of the most important methods of steganography on VoIP
called echo hiding is improved. This method has advantages in maintaining the
statistical and perceptual characteristics of audio signals as well as security
against the sensitivity of the human audio system (HAS). However, it has lots
of errors in detecting coded and hidden messages, which is detectable using
existing steganalysis methods. The percentage of extracting messages in these
improved methods of echo hiding is high, but they lower the security of the
method. In this article, a method is presented to improve the method of
extracting echo hiding, and enhance its security through a combined method
based on spread spectrum. To improve the extraction, a wrong hypothesis is
corrected and substituted. To improve security using a pseudo-random key
generation algorithm, spread spectrum and echo hiding methods are used
randomly. To evaluate the proposed extraction, numerous extraction tests are
carried out in the normal state and in the event of attacks. A steganalyser has
also been used to assess security improvements. The results gained through
different experiments on the security of steganography indicate a 3-percent
increase in steganalysis errors. The proposed extraction method was modified
based on the main method and resulted in more than 10% improvement.
