Crypto–stego interaction is not very well researched, yet
Combining steganography with cryptographic mechanisms in steganographic systems opens new pitfalls: Cryptographic methods tend to be well inspected for their stand-alone purpose, but have to fulfil additional assumptions when used as part of steganographic systems.
Judging from our experience, we have the impression that these particularities are often violated in steganographic context. Hence, there is potential for new successful attacks.
In brief:
Cryptographic methods have to meet additional requirements when used as part of steganographic systems