Comment:

Preconditions and Post Conditions are duplicated (in the images and in the text). I suggest removing from both images.

Important1: The sentence "A secure information transport … " (second item of the preconditions of the image) is missing in the text. I recommend adding this item in the text.

Important2: The sentence "If the Communication contains … " (second sentence of post conditions of the first image) is missing in the text. I recommend adding this item in the text.

Summary:

Preconditions and Post Conditions are duplicated (in the images and in the text)