A hallmark of the professions is the requirement that members of the profession keep certain information of their client secret or confidential. Confidentiality is mentioned in most engineering codes
Of ethics. This is a well- established principle in professions such as medicine, where the patient's medical information must be kept confidential, and in law, where attorney- client privilege is a well- established doctrine. 
This requirmation applies equally to engineers, who have an obligation to keep proprietary information of their employer or client confidential.