  We construct multipartite entangled states with underlying W-type structure
satisfying positive partial transpose (PPT) condition under any (N-1)|1
partition. Then we show how to distill N-partite secure key form the states
using two different methods: direct application of local filtering and novel
random key distillation scheme in which we adopt the idea form recent results
on entanglement distillation. Open problems and possible implications are also
discussed.
