  Two recently published papers propose some very simple key distribution
schemes designed to enable two or more parties to establish a shared secret key
with the aid of a third party. Unfortunately, as we show, most of the schemes
are inherently insecure and all are incompletely specified - moreover, claims
that the schemes are inherently lightweight are shown to be highly misleading.
We also briefly critique a somewhat related very recent paper by the same
authors that uses similar techniques to achieve what are claimed to be secure
multiparty computations.
