Key agreement scheme based on generalised inverses of matrices

For original paper see E. Dawson and C.-K. Wu, ibid., vol.33, no.14, pp.1210-11 (1997). Dawson and Wu proposed a key agreement scheme based on generalised matrix inverses. They suggest that for a key length of kn, using matrices of size k×m and m×n, with k⩽m⩽n the security parameter should be at least 2^(m-k)n . We give an attack for which the security parameter is at most 2 ^k2, and a second attack which applies in at least 28% of cases and reduces the original 2^(m-k)n to 2^(m-k)m m³