A technothriller, less improbable than some, involving computers, cryptography, and government paranoia. In Brown's hard-working debut, Commander Trevor Strathmore, the NSA's deputy director of operations, has invented TRANSLTR, a top-secret super-computer that by brute force can crack any encryption code in an hour or two. Then Strathmore discovers Digital Fortress, an encryption algorithm written by crippled ex- NSA genius Ensei Tankado, that the TRANSLTR can't break, so he calls in his head of cryptography, Susan Fletcher, to help. Seems that Tankado has posted a copy of Digital Fortress, encrypted with its own algorithm, on the Internet and has offered to sell his password to the highest bidder. But then Tankado turns up dead in Spain, his ring (with a copy of the password) missing, so Strathmore dispatches linguist David Becker (Susan's significant other) to get the ring. What neither Susan nor Becker knows is that Strathmore has his own agenda concerning Digital Fortress and Becker (he's in love with Susan and intends for Becker to be killed). Susan, meanwhile, searches for Tankado's partner, codenamed NDAKOTA, and the other copy of the password. Her suspicions focus on obnoxious coworker Greg Hale and his e-mail account. Becker finds the ring but then is shot--just as Susan and the NSA bigwigs slowly come to understand the effects of Strathmore's plotting: He's accidentally infected TRANSLTR with a computer worm that will leave the NSA's files open to hackers everwhere! Finally, just as the NSA's defenses collapse, Becker rises from the apparently dead to produce the magic ring. Inordinately complicated but reasonably exciting; should find a home in the middle reaches of the intelligence-bureau/techno-whiz readership.