1. A compact dual function Random Number Generator (RNG) and Stream Cipher Generator (SCG) including a Crypto-engine and a controller for controlling the Crypto-engine to operate either as a RNG or a SCG, including three muliplexers controlled by the controller to supply signals selectively to and receive signals from the Crypto-engine, in which a first multiplexer is arranged to receive RNG seed signals or SCG key signals, a second multiplexer is arranged to receive dynamic synchronization parameter signals or constant synchronization signals, and a third multiplexer is arranged to receive signals from the Crypto-engine and provide Random Number output signals or Stream Cipher output signals, respectively in each case.