Ask Ron Rivest if he's ever been whisked away by the CIA in the middle of the night, and he laughs-but he doesn't say no. At Peppercoin, a two-year-old MIT spinoff in Waltham, MA, the renowned cryptographer oversees an operation far less secretive than an intelligence agency but almost as intense: a clearinghouse for electronic "micropayments," pocket-change transactions that may finally allow magazines, musicians, and a multitude of others to profit from selling their wares online. It's September, and with only weeks to go until commercial launch, Peppercoin's software engineers troubleshoot at all hours. Marketing executives shout across the room and over the phone, making deals.

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