Security's inseparable couple

The most familiar names in network security are neither vendors nor geeks: Try Alice and Bob.

Since Ron Rivest, Adi Shamir and Len Adleman - the R, S and A in RSA Security - introduced Alice and Bob in their seminal public-key cryptosystem paper in 1978, the couple has become the subject of countless security-related papers, test questions, speeches and even, ahem, jokes.

Alice and Bob were the names given to fictitious characters used to explain how the RSA encryption method worked, with the thinking being that using names instead of letters like A and B would make a complex subject easier to grasp. They are so commonly used that most security experts don't even give a second thought to reaching for them.

"They're like old friends," says Charles Kolodgy, research director for security products at IDC. "I use them the same way everyone else does. 'So the sender, Alice, is trying to message Bob. . . .'"

"I use them conversationally. Sometimes I use them in documents, as well," says James Cupps, information security officer at Sappi Fine Paper North America in Portland, Maine. "I often use them in training because they are easier than Machine A and Machine B."

Over the years, the Alice and Bob story line has become more complicated, something of a high-tech reality show. Not only are Alice and Bob trying to share a secret, say a Valentine's Day poem, but Carol and Dave want in and Eve is trying to eavesdrop. A whole cast of characters has been introduced to explain everything from micropayments to SSL to quantum cryptography.

"Cryptography is the one area of mathematics where there are people, not just numbers," says Bruce Schneier, CTO of Counterpane Internet Security and author of Applied Cryptography , a book first published in 1994 that includes a table of "dramatis personae" headed by Alice and Bob.. "Alice and Bob are the links between the mathematical variables and the people."

Whitfield Diffie, Sun's chief security officer and co-author of the Diffie-Hellman key agreement protocol, says there is seemingly no end to this modern day Dick and Jane's adventures.

"[They have] appeared in fanciful circumstances in numerous papers carrying on their stormy relationship entirely over unprotected communication media and against the plots of their exes, the secret police.," he says.

One gossipy headline in a trade journal teased: "Alice and Bob grow apart." Some suspect the names stem from the swinging 1960s movie "Bob & Carol & Ted & Alice."