The world-wide growth of the mobile-telephony market opens the door for mobile commerce (m-commerce). For the restricted target platforms used for m-commerce such as mobile phones or personal digital assistants, domain solutions need to be lean but still secure. Especially mobile contracting and mobile payment as parts of m-commerce require solutions resting upon a sound legal basis. Electronic contracts and slips require solutions that are admitted as evidence in court. This is considered a key aspect for m-commerce applications to be widely accepted. This paper presents the Hermes platform developed at the University of Constance. It is a lean and secure trading platform that utilizes digital signatures for authentication conforming with the European electronic-signature laws.