Why encrypt? I once heard Grace Hopper say that our next big task is to decide what information should be tossed out to reduce archival expense. This remark, juxtaposed with Fisher’s paper, leads inevitably to Early’s Second Law, “If it ain’t worth saving, it ain’t worth encrypting.” Fisher’s more modest thesis is, “Even if it is worth keeping, it’s not necessarily worth encrypting.”

Having said that, little else of note is in Fisher’s paper. Reading it will provide a rather pleasant, five-minute introduction for those who know nothing about computer security, but who are forced to deal with it.

The author discusses, briefly, some definitions: encryption, decryption, transposition, substitution, and the National Bureau of Standards Data Encrypti- on Standard. He presents some situations in which security can be provided without encryption: physical security, passwords, limited access (the Coca Cola formula). He also notes some areas where encryption cannot help: theft of plaintext copies, unauthorized use of terminals after the establishment of communications, physical destruction of encrypted data, modification of software that manipulates encrypted data, and fraud or theft by authorized users.

To repeat, this is a four-page primer, an overview, for the novice.