The Battery-Discharge-Model: A Class of Stochastic Finite Automata to Simulate Multidimensional Continued Fraction Expansion

We define an infinite stochastic state machine, the Battery– Discharge–Model (BDM), which simulates the behaviour of linear and jump complexity of the continued fraction expansion of multidimensional formal power series, a relevant security measure in the cryptanalysis of stream ciphers. We also obtain finite approximations to the infinite BDM, where polynomially many states suffice to approximate with an exponentially small error the probabilities and averages for linear and jump complexity of M–multisequences of length n over the finite field Fq, for any M , n, q.