Improved apparatus and methods for spatial light modulation are disclosed which utilize optical cavities having both front and rear reflective surfaces. The matrix material is plasticizable by the liquid plasticizer and the encapsulation of the active encapsulant is accomplished at a low temperature and under low shear conditions. In a preferred embodiment the method includes the step of pressing the mix against an embossed matrix to create an embossed decorative surface with high wear resistance. On receiving the user information, the license server assigns a leaf of a key-managed hierarchical tree structure to the client, generates a set of node keys as a device node key, sends to the client the device node key together with a leaf ID and a private key of the client in question, and records the user information in correspondence with the leaf ID. Reading the responses then tells whether the respondent initially responded with integrity, if so the assessment is validated.