A cryptographic hash function is proposed based on a simple physical model. The model contains two balls and a ring. Each ball moves and collides with the fixed ring. Message is modeled as perturbations, which influence the motions of balls. The final positions and velocities of the two balls are converted to hash value. Simulations demonstrate that the proposed simple physical model has excellent randomness and sensitivity properties. Moreover, it is more efficient than most well-known hash functions.

Key words: Collision, hash function, computation model, cryptographic application.