  The booming interest in adversarial attacks stems from a misalignment between
human vision and a deep neural network (DNN), i.e. a human imperceptible
perturbation fools the DNN. Moreover, a single perturbation, often called
universal adversarial perturbation (UAP), can be generated to fool the DNN for
most images. A similar misalignment phenomenon has recently also been observed
in the deep steganography task, where a decoder network can retrieve a secret
image back from a slightly perturbed cover image. We attempt explaining the
success of both in a unified manner from the Fourier perspective. We perform
task-specific and joint analysis and reveal that (a) frequency is a key factor
that influences their performance based on the proposed entropy metric for
quantifying the frequency distribution; (b) their success can be attributed to
a DNN being highly sensitive to high-frequency content. We also perform feature
layer analysis for providing deep insight on model generalization and
robustness. Additionally, we propose two new variants of universal
perturbations: (1) Universal Secret Adversarial Perturbation (USAP) that
simultaneously achieves attack and hiding; (2) high-pass UAP (HP-UAP) that is
less visible to the human eye.
