Analyzed the chaotic and cryptographic properties of a piecewise nonlinear map. a couple chaotic digital sys-tem was proposed based on perturbing which used the piecewise nonlinear. then a new approach to construct keyed Hash function was presented. The approach used the initial value of the couple chaotic system as the secret key and the coarse-graining trajectory as Hash values. https://sportshutes.shop/product-category/trigger-locks/