The author of this paper is employed by Philips Usfa in the development of cryptographic equipment. As a consequence, he is appropriately equipped to present some deliberations on practical encryption applications.

In this paper, he addresses the question of key management in a large network which employs “classical” (symmetric, secret key) end-to-end encryption procedures. In particular, it is assumed that a unique key is available for each pair of terminals which may intercommunicate. The specific requirements for key storage at each terminal are then considered.

In what is perhaps the most obvious arrangement for an N-terminal network, each terminal must accommodate N − 1 distinct keys (i.e., one for each other terminal in the network). An alternative scheme is presented, where the network is subdivided in such a fashion that the storage requirement grows in a logarithmic manner as the network size is increased.

Those involved in the practical application of encryption schemes will find this paper both interesting and easy to read.