The General Formula and Algorithm of the Discretized Baker Map

It is effective and prevalent to use chaos for encryption. But some chaotic stream ciphers are weak for dynamical degradation. By iterating the discretized baker map we can pseudo-randomly permutated the pixels in a plain-image and obtain a cipher-image. It is difficult to break the encryption and no successful attack has been reported now. But there isn´t a general formula for the discretized baker map. It usually requires keys to be divisors of the size of plain-image, so it causes the whole key space to be very small. This paper proposes a general formula and a simple algorithm. The result proved by computer simulations