Mr. Moss, perhaps the epitome of a hacker who has jettisoned anonymity and entered the public sphere, has had an evolving relationship with aliases. Like many of his early online friends, he was interested in hacking and phone phreaking (the manipulation of telecommunications systems) — “stuff that wasn’t really legal,” he said. Aliases provided cover for such activity. And every once in a while, he explained — if a friend let slip your name, or if you outgrew a juvenile, silly alias — you’d have to burn your identity and come up with a new name.

“In my case, I had a couple previous identities,” he said, “but when I changed to The Dark Tangent, I was making a clear break from my past. I’d learned how to manage identities; I’d learned how the scene worked.”

He also remembers when everything changed. During the dot-com boom, many hackers transitioned to “real jobs,” he said, “and so they had to have real names, too.”

“My address book doubled in size,” he said with a laugh. And in time, as Defcon’s popularity ballooned, his list of formal appointments grew, too: membership at the Council on Foreign Relations, a seat on President Obama’s Homeland Security Advisory Council.

“The thing I worry about today,” he added, taking a more serious tone, “is that people don’t get do-overs.” Young people now have to contend with the real-name policy on Facebook, he said, along with the ever-hovering threats of facial-recognition software and aggregated data. “How are you going to learn to navigate in this world if you never get to make a mistake — and if every mistake you do make follows you forever?”