Abstract: A security feature is produced on a flat substrate, e.g. on paper or board. Particles—forming a cryptographic random pattern—are applied, preferably scattered on, to the substrate or incorporated into the substrate. Flexible pieces of wire or fiber, in particular thin pieces of copper wire, are applied to or incorporated into the substrate in a feature area corresponding to the security feature. The security feature can be provided with a protective layer, e.g. a laminate. A security feature produced in accordance with the invention can be detected simply and faultlessly and evaluated cryptographically. Furthermore, it cannot be imitated, or can be imitated only uneconomically, with known printing processes.