Janus is a cryptographic engine that may reside either in the computer that serves as an interface between a local network and the Internet, or in each computer attached to the local network. In the latter case, each Janus engine interacts with a proxy function in the computer acting as the network’s Internet interface. Janus provides ersatz identities to hide the identities of the local network’s users so that they can use Internet servers without revealing their true identities or permitting tracking of which servers each of them uses.

Janus also provides similarly pseudonymous email capability, supports both strong and weak encryption, and relieves individual users of burdens associated with secure interaction with Internet servers.

The authors give a complete, clear, and useful description of what they have done with Janus and an associated tool, the Lucent Personalized Web Assistant, and an illuminating discussion of the real-world problems they encountered and how they solved each.

Although some readers may regard the authors’ methods as fairly straightforward, they represent an insightful approach to requirements that may be both common and nettlesome.