For Eddy Zillan’s bar mitzvah in 2012, his parents gave him $5,000 to start an investment fund. They expected him to start dabbling in stocks. Instead, he began buying cryptocurrencies like bitcoin and ethereum.

Eddy saved up another $7,000 from summers spent working at a tennis club and other jobs, adding that to his investment fund for a total $12,000 in principal.

Anybody who has been following cryptocurrencies knows where this story is going: Eddy’s $12,000 investment is now worth well over $500,000, a return exceeding 4,100% in just a few years.

“I don’t know if he’s a prodigy, but he’s close,” says Eddy’s father, Gary Zillan. Eddy, now 18, is a high school senior in Orange, Ohio, near Cleveland. He hopes to study dentistry next year at Case Western Reserve University. But if that doesn’t work out, he has a Plan B, since he just launched a company that provides tutorials and insights on cryptocurrencies. “Hopefully he’ll be a multimillionaire by the time he’s my age,” says his father, who is 46.

View photos Eddy Zillan, 18, of Orange, Ohio, has amassed well over $500,000 worth of bitcoin and other cryptocurrencies. (Photo courtesy of Eddy Zillan) More

Bitcoin and other cryptocurrencies are suddenly the hottest investment since the dot-com bubble, after a stunning surge in value during the last year.

The price of bitcoin, the most well-known cryptocurrency, has soared by more than 700% in 2017. Ethereum is up a mind-boggling 3,900% — and early purchasers are suddenly watching the zeroes multiply on their accounts. Many crypto investors are reluctant to talk about their holdings, since alt-currencies are still associated with illicit activity, and they tend to appeal to non-traditionalists in the first place. But we found some willing to tell us their experiences. There are also plenty of detractors who insist cryptocurrencies are Ponzi schemes or worse. Yet regulators may soon bestow validity on cryptocurrencies by allowing broader investments, such as exchange-traded funds (ETFs), to track their value.

The origins of bitcoin

Bitcoin is a digital payment system launched in 2009 by a person or group using the name Satoshi Nakamoto. A network of coders with powerful computers has slowly “mined” more bitcoin since then by running complex computations that adhere to a set of founding principles, making bitcoin a kind of crowd-sourced currency. The market value of all bitcoin in the world is around $132 billion at current prices, roughly comparable to the current value of McDonald’s (MCD).

Other cryptocurrencies, sometimes referred to as “altcoins,” have emerged as well, including ether, the token of the blockchain network ethereum ($32 billion in market cap), ripple ($9 billion), litecoin ($3.7 billion) and dash ($3.3 billion).

In a recent Yahoo Finance survey, 77% of respondents told us they have never purchased bitcoin — but of those, 11% said they’re planning to, and 38% said they’re thinking about it. As more people buy in, that interest alone could send the crypto rally even higher.

[See the full results of our bitcoin survey, conducted online Nov. 10-13.]

Ordinary people can buy cryptocurrencies through services like Coinbase, SpectroCoin or Kraken, usually by linking a bank account or credit card and following simple instructions. (Disclosure: I own a small amount of bitcoin.)

View photos Of 1,011 poll respondents saying they’ve purchased Bitcoin, 71% have made money. Source: Yahoo Finance survey conducted via SurveyMonkey More

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