This work presents hyperchaos synchronization between two identical hyperchaotic systems by using nonlinear control
technique. This technique is applied to achieve chaos synchronization for two identical hyperchaotic complex Chen systems. The
idea of hyperchaos synchronization is to use the output of the drive system to control the response system so that the output of the
response system follows the output of the drive system asymptotically. Lyapunov functions are derived to prove that the error systems
are asymptotically stable. Expressions are derived for the control functions which are used to achieve chaos synchronization. Numerical
simulations show the validity of these expressions.