Let q = p r be a power of an odd prime p. We study binary sequences σ = (σ 0 , σ 1 , . . .) with entries in {0, 1} defined by using the quadratic character χ of the finite field F q :Our first contribution is to prove a lower bound on the linear complexity of σ for r ≥ 2. The bound improves some results of Meidl and Winterhof. Our second contribution is to study the k-error linear complexity of σ for r = 2. It seems that we cannot settle the case when r > 2 and leave it open. keyword: stream cipher; pseudorandom binary sequences; linear complexity; k-error linear complexity; discrete logarithm; finite field