  With the popularization and application of privacy protection technologies in
cloud service and social network, ciphertext has been gradually becoming a
common platform for public to exchange data. Under the cover of such a
plat-form, we propose steganography in encrypted domain (SIED) in this paper to
re-alize a novel method to realize secret communication Based on Simmons' model
of prisoners' problems, we discuss the application scenarios of SIED. According
to the different accesses to the encryption key and decryption key for secret
mes-sage sender or receiver, the application modes of SIED are classified into
four modes. To analyze the security requirments of SIED, four levels of
steganalysis attacks are introduced based on the prior knowledge about the
steganography system that the attacker is assumed to obtain in advance. Four
levels of security standards of SIED are defined correspondingly. Based on the
existing reversible data hiding techniques, we give four schemes of SIED as
practical instances with different security levels. By analyzing the embedding
and extraction characteris-tics of each instance, their SIED modes, application
frameworks and security lev-els are discussed in detail.
