Abstract: A digital encryption structure allows the varying of the computational overhead by selectively reusing, according to the desired level of security, a pseudorandom encoding sequence at the transmitter end and by storing and reusing pseudorandom decoding sequences, associated with one or more transmitters at the receiver end. A public initialization vector is combined with a secret key to produce a deterministic sequence from a pseudorandom number generator. This pseudorandom sequence in turn, is used to convert plaintext to ciphertext. The sequence may be selectively reused by storing the sequence to a transmitter memory cache and iteratively reading the sequence from memory according to a counter which controls the level of security of the encryption system. The ciphertext is decrypted on the receiver end by invertibly combining the ciphertext with the same pseudorandom sequence used by the transmitter to originally encode the plaintext.

Abstract: A three degrees of freedom interactive display controller device is disclosed, comprising a hand manipulable housing unit having an opening for the passage of a mouse ball, two motion detectors for detecting the movement of the mouse ball and converting that motion to output signals controlling the translational movement of an object on the display of a computer and at least one finger operated wheel or roller for controlling the translational motion of the object with respect to a third translational axis. All translation controls are operable to be physically moved in a direction which corresponds to the desired simulated direction of movement of the object on the display. The physical motion of each control is unbounded and the actual physical position of the housing unit is independent of the simulated position of the object on the display.