Lock and key

A system of encryption whereby something (the ‘key’) is required to decode the message. The ‘key’ is usually a handheld device which renders meaningful that which was previously unintelligible. Public keys may be disseminated widely, whereas private keys are...


A collective term for the effects of colour change or other visible characteristics under different sources of illumination.

Line-width modulation

Manipulating the width, length and height of line structures to create image and text effects. Using a higher resolution for the output results in effects not possible with commercially available software.

Liquid crystal

A state of matter with properties between those of conventional liquids and solid crystals. Orientation of the crystal-like structures is possible resulting in optically variable effects. Liquid crystal technology is used for security features based on polarisation...