Interleavers are key devices in most digital transmission systems. An approach for blind estimation of the interleaver length, as well as the encoder rate and constraint length, is proposed in this paper. The approach is based on linear algebra. We show that the rank of a matrix built from the intercepted interleaved stream falls when the number of rows of this matrix is a multiple of the interleaver length. Furthermore, the values of the ranks allow to estimate the encoder rate and constraint length. Typical applications are transmission surveillance and self-recovering receivers.